From Newsgroup: uk.d-i-y

I was doing a summary for a mate and thought I might as well add it to the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons
--
Cheers, Rob
Sheffield, UK
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

RJH <patchmoney@gmx.com> wrote:

I was doing a summary for a mate and thought I might as well add it to the Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

I realise this is just a dump of an email, but it's a bit broad brush and
could do with being more specific and citing details. I think it's useful
as a kind of 'things to ask' checklist, perhaps organised as bullet points?

Some comments:

MCS registration (you canrCOt export/import without it) shouldnrCOt take longer than a couple of weeks rCo IrCOve known it take years, or if they go bust, never. Ask them how long it takes.

You *can* export without MCS. Octopus at least will accept a standard electrical installation certificate issued by any sparky who is registered
with one of the bodies like NICEIC, Elecsa, etc (basically any sparky who
can do notifiable work, rather than handyman types). Octopus charge -u250
for doing the paperwork to enable you.

There's also the 'plug in solar' route, which is becoming available. We
don't know what will happen about export there (probably no export, but if a smart meter is in place maybe some supplier will allow it?)

You can of course import without restriction, just like every house in the country imports from the grid.

The 'I've known it take years' comment could really do with some evidence.
Was it a bloke down the pub who told you this story, was it written up in a newspaper, etc?

Ask if their installations are compatible with the main energy companies rCo Eon and Octopus especially.

Every installation is compatible with every energy company - it's just kWh exported. What you're talking about is 'smart' features where your import/export is set by an hourly tariff - this is only relevant if you have
a battery (or an EV). For those it needs to support the API that gets them
the hourly tariff data.

Inverters rCo quite large (suitcase sized). Check efficiency (in terms of inverting, and idle power consumption) and susceptibility to ambient temperatures rCo failures reported in hot/attic locations. Check the
maximum loads it can deal with rCo 3kWhr typical and may not be enough if
you want to run a shower independently from the grid. On which, see about EPS rCo emergency power supply whereby the system can run off grid. Complexity varies between whole house to a single socket.

Inverters can also be small, as in microinverters the size of a VHS cassette which often live on the back of panels.

Loads are in kW not kWh.

Your DNO will say how much export you are allowed. The paperwork (G98) is easier if it's less than 16A per phase (3.68kW single-phase), as above this (G99) the DNO can impose restrictions and needs to pre-approve the design.
You can have a larger inverter to eg charge batteries as long as the export
is capped to the allowed G98/G99 limit.

Batteries rCo check bulk fits (5 kWhr about the size of a suitcase and c.100kg). ideal capacity rCo difficult to know rCo somewhere between 5 and 20
kWhrs. The capacity chosen is never quite right, largely because future pricing and patterns of use are unknowable. For example, current deals
offer off-peak electricity at a 75% discount. So you could almost live off-grid if you have a large enough battery, with needs met by discounted grid and solar. And pricing of batteries seems to be unstable. Whatever
you choose, check that the system if modular rCo easy to bolt on additional batteries.

Battery size also depends on the loads you have. Do you run lots of stuff
like computers 24/7? Do you have electric heat like a heat pump, or is
heating gas?

I don't think 'pricing of batteries' is unstable: pricing of batteries is coming down. Perhaps that trend may reverse at some point, but predicting
the future is hard. Increasingly it's the cost of the packaging that's dominating rather than the cost of the cells themselves.

New tech like sodium ion may help to reduce packaging costs - eg as it'll
work in sub-zero conditions it can be happily mounted outside. Sodium ion
is also cheaper as the materials are abundant.

Another thing is distributed v centralised battery. Some battery systems
are standalone in that they just connect to 230v AC, while others are integrated with the solar inverter. Integrated systems are cheaper, but
mean you have to put solar inverter and battery in the same place. With a
230v AC connection you can put batteries in any location that has mains, and
if you need more battery then just buy another one (with its own inverter)
and add it in another spot on your existing 230v wiring. Then they're operating independently, although software to integrate systems from
multiple vendors is more tricky (a third party system like Home Assistant
may be helpful here).

Choice of panels rCo check the output (500W is good for a standard panel)
and efficiency (get as close to 25% as you can), reputation of
manufacturer, technology. Size and choice also will depend on pitch, shading, and guarantee (including cell degradation). Cost isnrCOt a major variable in the scheme of things rCo choose the best you can, donrCOt look at the cost (within reason!).

The higher wattage panels are bifacial, meaning they have cells both sides. You might get that if using them as a fence, or above a light-coloured roof surface where a lot of light is reflected to the back side. If you are
putting them right up against a dark coloured roof you won't get much
benefit from being bifacial (I think the bifacial bit gives a ~15% boost to output, which you won't get).

Ask about anti-bird nesting protection. benefits appear mixed.

What's mixed, ooi? It's just some spikes to stop birds getting behind the panels - eg if they don't nest they may sit and crap on the panels which is
not great for efficiency.

snow puts a lot of stress on it

ah, I hadn't thought about that. I could imagine all sorts of problems with ice dams and whatnot.

anything but north-facing works

According to: https://globalsolaratlas.info/detail?c=52.479699,-1.902691,11&s=52.479699,-1.902691&m=site&pv=small,180,37,1
https://globalsolaratlas.info/detail?c=52.479699,-1.902691,11&s=52.479699,-1.902691&m=site&pv=small,0,37,1

for a site in Birmingham, north-facing gets about half the output as south facing. For a 1kW panel you get 458 kWh/y instead of 935kWh/y.

So north facing still 'works', but it doesn't work as well. Either way you need to do the sums - if you only have a N facing roof you can maybe still
make it work.


In general, I think I might be tempted to reframe the article as:

1. Gather some basic information about your site:
- potential locations for panels
- roof data (dimensions, angle of pitch, compass bearing, any sources of shading like chimneys or dormers)
- what your energy consumption profile looks through the day in spring,
summer, autumn, winter (eg smart meter data)
- what your electricity supply looks like (pictures of consumer unit, supply fuse, meter, etc)
- could you move more consumption to electric (EV, heat pump, induction hob, electric hot water)?

2. Calculate:
- how much roof area you have to play with
- how many panels you might reasonably fit (roughly speaking 1x2m panels at 500W each)
- roughly how much energy you might expect at different times of day and
times of year at your location (eg via globalsolaratlas)
- what you might do with that energy (eg run baseload, store in a battery for evening)
- can you practically timeshift appliances, eg dishwasher, tumble dryer, EV charging) to peak generation time

3. Start talking to installers being more informed about what you actually want.


I think there's a danger with a lot of the solar quoting surveys which just
ask 'how many panels do you want'; unless the answer is going to be 'as many
as will fit' you probably want to be somewhat informed about what sort of number fits what you're going to do with it.

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11 May 2026 at 12:01:05 BST, Theo wrote:

RJH <patchmoney@gmx.com> wrote:

I was doing a summary for a mate and thought I might as well add it to the >> Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

I realise this is just a dump of an email, but it's a bit broad brush and could do with being more specific and citing details. I think it's useful
as a kind of 'things to ask' checklist, perhaps organised as bullet points?

Yes, I can set it out a bit better, with context.

Some comments:

MCS registration (you canrCOt export/import without it) shouldnrCOt take
longer than a couple of weeks rCo IrCOve known it take years, or if they go >> bust, never. Ask them how long it takes.

You *can* export without MCS. Octopus at least will accept a standard electrical installation certificate issued by any sparky who is registered with one of the bodies like NICEIC, Elecsa, etc (basically any sparky who
can do notifiable work, rather than handyman types). Octopus charge -u250 for doing the paperwork to enable you.

There's also the 'plug in solar' route, which is becoming available. We don't know what will happen about export there (probably no export, but if a smart meter is in place maybe some supplier will allow it?)

Good to know, thanks.

You can of course import without restriction, just like every house in the country imports from the grid.

Yes.

The 'I've known it take years' comment could really do with some evidence. Was it a bloke down the pub who told you this story, was it written up in a newspaper, etc?

A friend/former colleague/neighbour. Pretty sure he's not lying. Mine took days. Maybe stress it's anecdote.

Ask if their installations are compatible with the main energy companies rCo >> Eon and Octopus especially.

Every installation is compatible with every energy company - it's just kWh exported. What you're talking about is 'smart' features where your import/export is set by an hourly tariff - this is only relevant if you have a battery (or an EV). For those it needs to support the API that gets them the hourly tariff data.

Thanks - I'll delete that bit. From memory some energy companies ask for details of installed kit - assumed that was because it might matter, but evidently not.

Inverters rCo quite large (suitcase sized). Check efficiency (in terms of >> inverting, and idle power consumption) and susceptibility to ambient
temperatures rCo failures reported in hot/attic locations. Check the
maximum loads it can deal with rCo 3kWhr typical and may not be enough if
you want to run a shower independently from the grid. On which, see about >> EPS rCo emergency power supply whereby the system can run off grid.
Complexity varies between whole house to a single socket.

Inverters can also be small, as in microinverters the size of a VHS cassette which often live on the back of panels.

Ah didn't know that - the ones I've seen are a lot larger.

Loads are in kW not kWh.

Yep :-)

Your DNO will say how much export you are allowed. The paperwork (G98) is easier if it's less than 16A per phase (3.68kW single-phase), as above this (G99) the DNO can impose restrictions and needs to pre-approve the design. You can have a larger inverter to eg charge batteries as long as the export is capped to the allowed G98/G99 limit.

Yes, I meant that in terms of the inverter -shoudl have been clearer. Mine comes in several versions - 3kW up to 16kW (I think).

Batteries rCo check bulk fits (5 kWhr about the size of a suitcase and
c.100kg). ideal capacity rCo difficult to know rCo somewhere between 5 and 20
kWhrs. The capacity chosen is never quite right, largely because future
pricing and patterns of use are unknowable. For example, current deals
offer off-peak electricity at a 75% discount. So you could almost live
off-grid if you have a large enough battery, with needs met by discounted
grid and solar. And pricing of batteries seems to be unstable. Whatever
you choose, check that the system if modular rCo easy to bolt on additional >> batteries.

Battery size also depends on the loads you have. Do you run lots of stuff like computers 24/7? Do you have electric heat like a heat pump, or is heating gas?

I don't think 'pricing of batteries' is unstable: pricing of batteries is coming down. Perhaps that trend may reverse at some point, but predicting the future is hard. Increasingly it's the cost of the packaging that's dominating rather than the cost of the cells themselves.

OK, thanks, I'll change that to stable, decreasing.

New tech like sodium ion may help to reduce packaging costs - eg as it'll work in sub-zero conditions it can be happily mounted outside. Sodium ion
is also cheaper as the materials are abundant.

Another thing is distributed v centralised battery. Some battery systems
are standalone in that they just connect to 230v AC, while others are integrated with the solar inverter. Integrated systems are cheaper, but
mean you have to put solar inverter and battery in the same place. With a 230v AC connection you can put batteries in any location that has mains, and if you need more battery then just buy another one (with its own inverter) and add it in another spot on your existing 230v wiring. Then they're operating independently, although software to integrate systems from
multiple vendors is more tricky (a third party system like Home Assistant
may be helpful here).

I'll copy/paste that if I may.

Choice of panels rCo check the output (500W is good for a standard panel)
and efficiency (get as close to 25% as you can), reputation of
manufacturer, technology. Size and choice also will depend on pitch,
shading, and guarantee (including cell degradation). Cost isnrCOt a major >> variable in the scheme of things rCo choose the best you can, donrCOt look at
the cost (within reason!).

The higher wattage panels are bifacial, meaning they have cells both sides. You might get that if using them as a fence, or above a light-coloured roof surface where a lot of light is reflected to the back side. If you are putting them right up against a dark coloured roof you won't get much
benefit from being bifacial (I think the bifacial bit gives a ~15% boost to output, which you won't get).

Yes, I was aware of bifacial - didn't realise it affected output on a piched roof/15cm from surface, live/learn, I'll mention that.

Ask about anti-bird nesting protection. benefits appear mixed.

What's mixed, ooi? It's just some spikes to stop birds getting behind the panels - eg if they don't nest they may sit and crap on the panels which is not great for efficiency.

Just something my installer told me - sometimes they don't work, stay fixed, damaged over time. Some installs no problems reported. Just be reasonably sure you need them was the point I was trying to get across.

snow puts a lot of stress on it

ah, I hadn't thought about that. I could imagine all sorts of problems with ice dams and whatnot.

My neighbour's was in her gutter after the only dusting of snow we had last winter.

anything but north-facing works

According to: https://globalsolaratlas.info/detail?c=52.479699,-1.902691,11&s=52.479699,-1.902691&m=site&pv=small,180,37,1
https://globalsolaratlas.info/detail?c=52.479699,-1.902691,11&s=52.479699,-1.902691&m=site&pv=small,0,37,1

for a site in Birmingham, north-facing gets about half the output as south facing. For a 1kW panel you get 458 kWh/y instead of 935kWh/y.

So north facing still 'works', but it doesn't work as well. Either way you need to do the sums - if you only have a N facing roof you can maybe still make it work.

Interesting. Again, didn't know that. 50% is a lot more than I expected. In fact I was on a course and an installer made clear they wouldn't install N-facing, and the room appeared to agree (well, no-one disagreed).

In general, I think I might be tempted to reframe the article as:

1. Gather some basic information about your site:
- potential locations for panels
- roof data (dimensions, angle of pitch, compass bearing, any sources of shading like chimneys or dormers)
- what your energy consumption profile looks through the day in spring, summer, autumn, winter (eg smart meter data)
- what your electricity supply looks like (pictures of consumer unit, supply fuse, meter, etc)
- could you move more consumption to electric (EV, heat pump, induction hob, electric hot water)?

2. Calculate:
- how much roof area you have to play with
- how many panels you might reasonably fit (roughly speaking 1x2m panels at 500W each)
- roughly how much energy you might expect at different times of day and times of year at your location (eg via globalsolaratlas)
- what you might do with that energy (eg run baseload, store in a battery for evening)
- can you practically timeshift appliances, eg dishwasher, tumble dryer, EV charging) to peak generation time

3. Start talking to installers being more informed about what you actually want.

I think there's a danger with a lot of the solar quoting surveys which just ask 'how many panels do you want'; unless the answer is going to be 'as many as will fit' you probably want to be somewhat informed about what sort of number fits what you're going to do with it.

Many thanks. I'll leave it a bit and come back to it when I have more time. Roof to get on :-)
--
Cheers, Rob
Sheffield, UK
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it to the Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery longevity),
under stairs cupboard (fire risk right under your primary means of
escape etc).
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 11/05/2026 15:15, John Rumm wrote:

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it to
the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery longevity), under stairs cupboard (fire risk right under your primary means of
escape etc).

There is now a whole lot of recent regulation (April 2026), previously
just recommendations. Batteries should not be installed in lofts,
bedrooms, under stairs or or less than 1m from doors and windows. and if fitted inside a house consideration must be given for a fire proof
enclosure and ventilation. Garages seem to be OK. Limited to 40kWh if
fitted inside a house.
--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 12/05/2026 07:27, alan_m wrote:

On 11/05/2026 15:15, John Rumm wrote:

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it
to the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery
longevity), under stairs cupboard (fire risk right under your primary
means of escape etc).

The battery on my installation weights 110kg. How could one get it into
a loft> or even upstairs?

There is now a whole lot of recent regulation (April 2026), previously
just recommendations. Batteries should not be installed in lofts,
bedrooms, under stairs or or less than 1m from doors and windows. and if fitted inside a house consideration must be given for a fire proof
enclosure and ventilation. Garages seem to be OK. Limited to 40kWh if
fitted inside a house.

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Charles Hope wrote:

On 12/05/2026 07:27, alan_m wrote:

On 11/05/2026 15:15, John Rumm wrote:

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it
to the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery
longevity), under stairs cupboard (fire risk right under your primary
means of escape etc).

The battery on my installation weights 110kg. How could one get it into
a loft> or even upstairs?

With difficulty ;-)

There is now a whole lot of recent regulation (April 2026), previously
just recommendations. Batteries should not be installed in lofts,
bedrooms, under stairs or or less than 1m from doors and windows. and
if fitted inside a house consideration must be given for a fire proof
enclosure and ventilation. Garages seem to be OK. Limited to 40kWh if
fitted inside a house.

Is this a good place to ask what batteries people are using? I'm not
convinced that solar makes sense for us, but a battery (or batteries) to
load shift from peak rate to off-peak might, especially if it can live
in a shed.

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 12 May 2026 at 10:15:02 BST, Charles Hope wrote:

On 12/05/2026 07:27, alan_m wrote:

On 11/05/2026 15:15, John Rumm wrote:

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it
to the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery
longevity), under stairs cupboard (fire risk right under your primary
means of escape etc).

The battery on my installation weights 110kg. How could one get it into
a loft> or even upstairs?

I think they're modular or disaassemble easily - maybe 4 x 25kg battery packs clip together inside the box sort of thing?

There is now a whole lot of recent regulation (April 2026), previously
just recommendations. Batteries should not be installed in lofts,
bedrooms, under stairs or or less than 1m from doors and windows. and if
fitted inside a house consideration must be given for a fire proof
enclosure and ventilation. Garages seem to be OK. Limited to 40kWh if
fitted inside a house.

Interesting, thanks. Quite hard to stay ahead of the curve . . .
--
Cheers, Rob
Sheffield, UK
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

RJH <patchmoney@gmx.com> wrote:

On 11 May 2026 at 12:01:05 BST, Theo wrote:

The 'I've known it take years' comment could really do with some evidence. Was it a bloke down the pub who told you this story, was it written up in a newspaper, etc?

A friend/former colleague/neighbour. Pretty sure he's not lying. Mine took days. Maybe stress it's anecdote.

As ever with these stories, it helps to get to the bottom of why there was a delay. Did they just not reply to attempts to contact them? Was some bit
of paper missing, that stalled the process because it was hard to generate? Did one party go bust before the process was completed?

ie is this a 'they take forever to do paperwork' problem, which could apply
to anyone, or a 'unusual circumstances happened' which caused the delay, and
if those circumstances don't happen to you (something you can maybe know in advance) then you're fine.

eg if you're having surgery for condition X, those people who also have condition Y make it much more risky and drag down the average. But if you don't have condition Y you know the odds are much better.

Newspaper reports tend to give a bit more detail which explain the delay, whereas fourth hand whispers down the pub don't.

Ask if their installations are compatible with the main energy companies rCo
Eon and Octopus especially.

Every installation is compatible with every energy company - it's just kWh exported. What you're talking about is 'smart' features where your import/export is set by an hourly tariff - this is only relevant if you have
a battery (or an EV). For those it needs to support the API that gets them the hourly tariff data.

Thanks - I'll delete that bit. From memory some energy companies ask for details of installed kit - assumed that was because it might matter, but evidently not.

Sometimes it's because they'll only offer the smart tariff if you have a compatible EV/charger/heatpump/etc that they can talk to. If you don't, they'll only offer their regular tariffs. eg 'Intelligent Octopus Go' needs
a compatible EV or charger that allows them to control the charging period,
but 'Octopus Go' will work with any.

Inverters rCo quite large (suitcase sized). Check efficiency (in terms of >> inverting, and idle power consumption) and susceptibility to ambient
temperatures rCo failures reported in hot/attic locations. Check the
maximum loads it can deal with rCo 3kWhr typical and may not be enough if >> you want to run a shower independently from the grid. On which, see about >> EPS rCo emergency power supply whereby the system can run off grid.
Complexity varies between whole house to a single socket.

Inverters can also be small, as in microinverters the size of a VHS cassette
which often live on the back of panels.

Ah didn't know that - the ones I've seen are a lot larger.

Microinverters mean each panel (pair) is a separate AC generator. ie you're just distributing 230V AC around the place rather than higher current DC wiring.

The downside of putting them on the back of panels is access can be a
problem if you need to replace them later - you might need to replace the inverter after 10 years but the panels after 20+. You could of course put
them somewhere else.

New tech like sodium ion may help to reduce packaging costs - eg as it'll work in sub-zero conditions it can be happily mounted outside. Sodium ion is also cheaper as the materials are abundant.

Another thing is distributed v centralised battery. Some battery systems are standalone in that they just connect to 230v AC, while others are integrated with the solar inverter. Integrated systems are cheaper, but mean you have to put solar inverter and battery in the same place. With a 230v AC connection you can put batteries in any location that has mains, and
if you need more battery then just buy another one (with its own inverter) and add it in another spot on your existing 230v wiring. Then they're operating independently, although software to integrate systems from multiple vendors is more tricky (a third party system like Home Assistant may be helpful here).

I'll copy/paste that if I may.

Feel free.

Microinverters are the same idea on the generation side. They're
particularly useful if you have several roof aspects, eg a complicated roof with only space for a panel or two on each section. Rather than trying to cable those back to a central inverter, and with quite different shading properties, you can just scatter panels and their microinverters about
wherever you can find spare roof.

I think you could add a section about shading. Panel output is reduced by shading, and when you put panels in series then shading of one panel can
reduce the current flowing through the whole string. Ideally you want the whole string to have similar shading, ie all face the same way, have nothing like chimneys or trees that might cast a shadow on one panel not all. But another thing you can do is have a power optimiser. This is a DC/DC
converter that runs each panel/group of panels at its optimum via Maximum
Power Point Tracking (MPPT), and then you combine those into a string
feeding into the big inverter. That makes the best out of each panel
without shading limiting the output.

Optimisers cost extra and are a bit similar to microinverters but without
the AC side, so they're cheaper but still a substantial fraction of the
cost of the panels.

Choice of panels rCo check the output (500W is good for a standard panel) >> and efficiency (get as close to 25% as you can), reputation of
manufacturer, technology. Size and choice also will depend on pitch,
shading, and guarantee (including cell degradation). Cost isnrCOt a major >> variable in the scheme of things rCo choose the best you can, donrCOt look at
the cost (within reason!).

The higher wattage panels are bifacial, meaning they have cells both sides. You might get that if using them as a fence, or above a light-coloured roof surface where a lot of light is reflected to the back side. If you are putting them right up against a dark coloured roof you won't get much benefit from being bifacial (I think the bifacial bit gives a ~15% boost to output, which you won't get).

Yes, I was aware of bifacial - didn't realise it affected output on a piched roof/15cm from surface, live/learn, I'll mention that.

It's a little bit of marketing inflating the numbers compared with what you might get in practice. OTOH if they can make bifacial for a small cost
delta and it gets you a bit more generation in some cases, then why not?

So north facing still 'works', but it doesn't work as well. Either way you need to do the sums - if you only have a N facing roof you can maybe still make it work.

Interesting. Again, didn't know that. 50% is a lot more than I expected. In fact I was on a course and an installer made clear they wouldn't install N-facing, and the room appeared to agree (well, no-one disagreed).

It would double your payback time, which maybe means the economics doesn't
work for a pro install. But if you were DIYing and could keep costs down
(eg no scaffolding) then maybe doubling payback from say 3 years to 6 is acceptable.

Installers just want an easy life and maybe aren't interested
in awkward jobs - eg this guy fitted vertical panels but had a hard time getting installers to do it because MCS didn't have an approved system: https://www.youtube.com/watch?v=PzbCg-tj77g
- but mounting flat things to a wall is hardly rocket science.

Basically any cost calculation is no longer about the panels any more, it's
all about the ancillaries (labour, scaffolding, mounting system). Those are where you can make the difference in payback times. Availability of the
'plug in' systems may help cut those costs down further - eg no need for MCS certification cutting labour costs.

Many thanks. I'll leave it a bit and come back to it when I have more time. Roof to get on :-)

Did you consider solar panels on that roof? :-)

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 12/05/2026 10:15, Charles Hope wrote:

The battery on my installation weights 110kg. How could one get it into
a loft> or even upstairs?

Eat your spinach...
--
Gun Control: The law that ensures that only criminals have guns.

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

RJH <patchmoney@gmx.com> wrote:

On 12 May 2026 at 10:15:02 BST, Charles Hope wrote:

On 12/05/2026 07:27, alan_m wrote:

On 11/05/2026 15:15, John Rumm wrote:

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it
to the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery
longevity), under stairs cupboard (fire risk right under your primary
means of escape etc).

The battery on my installation weights 110kg. How could one get it into
a loft> or even upstairs?

I think they're modular or disaassemble easily - maybe 4 x 25kg battery packs clip together inside the box sort of thing?

Many of them use 19" server-rack cases, so they come in lumps of 4U or 6U
that are installed in a 19" rack inside the outer chassis, and then wired
up. Typically everything operates using 48V. There may be a fancy cosmetic exterior so it looks less like a wiring closet from the outside.

https://www.fogstar.co.uk/collections/solar-battery-storage
has examples.

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 12 May 2026 at 12:59:37 BST, Theo wrote:

RJH <patchmoney@gmx.com> wrote:

On 11 May 2026 at 12:01:05 BST, Theo wrote:

The 'I've known it take years' comment could really do with some evidence. >>> Was it a bloke down the pub who told you this story, was it written up in a >>> newspaper, etc?

A friend/former colleague/neighbour. Pretty sure he's not lying. Mine took >> days. Maybe stress it's anecdote.

As ever with these stories,

This is something I followed from the beginning - not really 'a story'. The company was pretty useless by all accounts and is now dissolved.

it helps to get to the bottom of why there was a
delay. Did they just not reply to attempts to contact them? Was some bit
of paper missing, that stalled the process because it was hard to generate? Did one party go bust before the process was completed?

ie is this a 'they take forever to do paperwork' problem, which could apply to anyone, or a 'unusual circumstances happened' which caused the delay, and if those circumstances don't happen to you (something you can maybe know in advance) then you're fine.

eg if you're having surgery for condition X, those people who also have condition Y make it much more risky and drag down the average. But if you don't have condition Y you know the odds are much better.

Newspaper reports tend to give a bit more detail which explain the delay, whereas fourth hand whispers down the pub don't.

He never had an explanation.

Ask if their installations are compatible with the main energy companies rCo
Eon and Octopus especially.

Every installation is compatible with every energy company - it's just kWh >>> exported. What you're talking about is 'smart' features where your
import/export is set by an hourly tariff - this is only relevant if you have
a battery (or an EV). For those it needs to support the API that gets them >>> the hourly tariff data.

Thanks - I'll delete that bit. From memory some energy companies ask for
details of installed kit - assumed that was because it might matter, but
evidently not.

Sometimes it's because they'll only offer the smart tariff if you have a compatible EV/charger/heatpump/etc that they can talk to. If you don't, they'll only offer their regular tariffs. eg 'Intelligent Octopus Go' needs a compatible EV or charger that allows them to control the charging period, but 'Octopus Go' will work with any.

OK thanks, noted.

Inverters rCo quite large (suitcase sized). Check efficiency (in terms of >>>> inverting, and idle power consumption) and susceptibility to ambient
temperatures rCo failures reported in hot/attic locations. Check the
maximum loads it can deal with rCo 3kWhr typical and may not be enough if >>>> you want to run a shower independently from the grid. On which, see about >>>> EPS rCo emergency power supply whereby the system can run off grid.
Complexity varies between whole house to a single socket.

Inverters can also be small, as in microinverters the size of a VHS cassette
which often live on the back of panels.

Ah didn't know that - the ones I've seen are a lot larger.

Microinverters mean each panel (pair) is a separate AC generator. ie you're just distributing 230V AC around the place rather than higher current DC wiring.

The downside of putting them on the back of panels is access can be a
problem if you need to replace them later - you might need to replace the inverter after 10 years but the panels after 20+. You could of course put them somewhere else.

OK, thanks, didn't realise they were a thing.

New tech like sodium ion may help to reduce packaging costs - eg as it'll >>> work in sub-zero conditions it can be happily mounted outside. Sodium ion >>> is also cheaper as the materials are abundant.

Another thing is distributed v centralised battery. Some battery systems >>> are standalone in that they just connect to 230v AC, while others are
integrated with the solar inverter. Integrated systems are cheaper, but >>> mean you have to put solar inverter and battery in the same place. With a >>> 230v AC connection you can put batteries in any location that has mains, and
if you need more battery then just buy another one (with its own inverter) >>> and add it in another spot on your existing 230v wiring. Then they're
operating independently, although software to integrate systems from
multiple vendors is more tricky (a third party system like Home Assistant >>> may be helpful here).

I'll copy/paste that if I may.

Feel free.

Microinverters are the same idea on the generation side. They're particularly useful if you have several roof aspects, eg a complicated roof with only space for a panel or two on each section. Rather than trying to cable those back to a central inverter, and with quite different shading properties, you can just scatter panels and their microinverters about wherever you can find spare roof.

I think you could add a section about shading. Panel output is reduced by shading, and when you put panels in series then shading of one panel can reduce the current flowing through the whole string. Ideally you want the whole string to have similar shading, ie all face the same way, have nothing like chimneys or trees that might cast a shadow on one panel not all. But another thing you can do is have a power optimiser. This is a DC/DC converter that runs each panel/group of panels at its optimum via Maximum Power Point Tracking (MPPT), and then you combine those into a string
feeding into the big inverter. That makes the best out of each panel
without shading limiting the output.

Yes, thanks, I do mention shading more than once, but more detail could be included. As it happens the person I wrote in for is unlikely to be affected
by shading.

Optimisers cost extra and are a bit similar to microinverters but without
the AC side, so they're cheaper but still a substantial fraction of the
cost of the panels.

Choice of panels rCo check the output (500W is good for a standard panel) >>>> and efficiency (get as close to 25% as you can), reputation of
manufacturer, technology. Size and choice also will depend on pitch,
shading, and guarantee (including cell degradation). Cost isnrCOt a major >>>> variable in the scheme of things rCo choose the best you can, donrCOt look at
the cost (within reason!).

The higher wattage panels are bifacial, meaning they have cells both sides. >>> You might get that if using them as a fence, or above a light-coloured roof >>> surface where a lot of light is reflected to the back side. If you are
putting them right up against a dark coloured roof you won't get much
benefit from being bifacial (I think the bifacial bit gives a ~15% boost to >>> output, which you won't get).

Yes, I was aware of bifacial - didn't realise it affected output on a piched >> roof/15cm from surface, live/learn, I'll mention that.

It's a little bit of marketing inflating the numbers compared with what you might get in practice. OTOH if they can make bifacial for a small cost
delta and it gets you a bit more generation in some cases, then why not?

Quite - especially for the 15%. My installer didn't even mention them. And I didn't think to ask, given my application (standard pitched roof). Live and learn :-)

So north facing still 'works', but it doesn't work as well. Either way you >>> need to do the sums - if you only have a N facing roof you can maybe still >>> make it work.

Interesting. Again, didn't know that. 50% is a lot more than I expected. In >> fact I was on a course and an installer made clear they wouldn't install
N-facing, and the room appeared to agree (well, no-one disagreed).

It would double your payback time, which maybe means the economics doesn't work for a pro install. But if you were DIYing and could keep costs down
(eg no scaffolding) then maybe doubling payback from say 3 years to 6 is acceptable.

Installers just want an easy life and maybe aren't interested
in awkward jobs - eg this guy fitted vertical panels but had a hard time getting installers to do it because MCS didn't have an approved system: https://www.youtube.com/watch?v=PzbCg-tj77g
- but mounting flat things to a wall is hardly rocket science.

Basically any cost calculation is no longer about the panels any more, it's all about the ancillaries (labour, scaffolding, mounting system). Those are where you can make the difference in payback times. Availability of the 'plug in' systems may help cut those costs down further - eg no need for MCS certification cutting labour costs.

Yes, I do mention that, but could add more detail.

Many thanks. I'll leave it a bit and come back to it when I have more time. >> Roof to get on :-)

Did you consider solar panels on that roof? :-)

Good point! It's actually got a half-decent aspect . . . but it's only 2.5m x 1.5m, and tapping it in to the existing system is likely to be the biggest
cost (common theme developing).
--
Cheers, Rob
Sheffield, UK
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

RJH <patchmoney@gmx.com> wrote:

On 12 May 2026 at 12:59:37 BST, Theo wrote:

RJH <patchmoney@gmx.com> wrote:

On 11 May 2026 at 12:01:05 BST, Theo wrote:

The 'I've known it take years' comment could really do with some evidence.
Was it a bloke down the pub who told you this story, was it written up in a
newspaper, etc?

A friend/former colleague/neighbour. Pretty sure he's not lying. Mine took >> days. Maybe stress it's anecdote.

As ever with these stories,

This is something I followed from the beginning - not really 'a story'. The company was pretty useless by all accounts and is now dissolved.

OK, so that's 'the company can't be bothered' rather than any systemic
problem. Your job as client is to choose a company who can be bothered, not
a bunch of cowboys.

(I think there is an escalation path via MCS, but not sure how that works)

Yes, I was aware of bifacial - didn't realise it affected output on a piched
roof/15cm from surface, live/learn, I'll mention that.

It's a little bit of marketing inflating the numbers compared with what you might get in practice. OTOH if they can make bifacial for a small cost delta and it gets you a bit more generation in some cases, then why not?

Quite - especially for the 15%. My installer didn't even mention them. And I didn't think to ask, given my application (standard pitched roof). Live and learn :-)

If the panels are bifacial, be aware that the power output numbers for the panels include the bifacial aspect. So butted up against a dark roof you
might expect a ~15% drop in output because there's nothing to reflect light
to the back side.

Did you consider solar panels on that roof? :-)

Good point! It's actually got a half-decent aspect . . . but it's only 2.5m x 1.5m, and tapping it in to the existing system is likely to be the biggest cost (common theme developing).

It sounds perfect for a 'plug in solar' install with a panel and a microinverter. Just needs a mains connection, could be via a FCU. Wait for them to show up in Lidl...

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 12/05/2026 10:15, Charles Hope wrote:

On 12/05/2026 07:27, alan_m wrote:

On 11/05/2026 15:15, John Rumm wrote:

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it
to the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery
longevity), under stairs cupboard (fire risk right under your primary
means of escape etc).

The battery on my installation weights 110kg. How could one get it into
a loft> or even upstairs?

Many are modular - installed in more modest units that can be ganged
together.
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk | \=================================================================/
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 12/05/2026 21:22, John Rumm wrote:

On 12/05/2026 10:15, Charles Hope wrote:

On 12/05/2026 07:27, alan_m wrote:

On 11/05/2026 15:15, John Rumm wrote:

On 11/05/2026 11:12, RJH wrote:

I was doing a summary for a mate and thought I might as well add it >>>>> to the
Wiki . . . hope it's appropriate, and obvs edit at will.

https://wiki.diyfaq.org.uk/index.php?title=Solar:_Pros_and_Cons

Perhaps a section on locations for battery installs. Quit often
installers seem to go for places that are "easy" but not necessarily
ideal, e.g. lofts (high temperature swings bade for battery
longevity), under stairs cupboard (fire risk right under your
primary means of escape etc).

The battery on my installation weights 110kg. How could one get it
into a loft> or even upstairs?

Many are modular - installed in more modest units that can be ganged together.

There seems to be a trend for exterior wall mounted batteries so the
form factor is different from rack mounted stuff like pylontech.

The advantage of pylontech is that they are fairly catholic to
paralleling batteries of different ages.

It is apparently possible to parallel different makes of battery as long
as they contain the same number of, same chemistry, cells in series by intercepting the CANbus signals from the inverter and spoofing them so
the battery sees what it expects but that has proved beyond me.I still
have a redundant 6.5kWh ac coupled battery and inverter I would like to
make use of,(the battery at least).

My set up has been a decent cost saving investment in 10 years of
retirement, my total gas and electric bills last year was -u62.

I only use gas for DHW in winter and the only reason not to have it cut
off is I think it would make a house sale difficult plus I have a
cunning plan.
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

AJH <news@loampitsfarm.co.uk> wrote:

There seems to be a trend for exterior wall mounted batteries so the
form factor is different from rack mounted stuff like pylontech.

The advantage of pylontech is that they are fairly catholic to
paralleling batteries of different ages.

It is apparently possible to parallel different makes of battery as long
as they contain the same number of, same chemistry, cells in series by intercepting the CANbus signals from the inverter and spoofing them so
the battery sees what it expects but that has proved beyond me.I still
have a redundant 6.5kWh ac coupled battery and inverter I would like to
make use of,(the battery at least).

If the battery comes with its own inverter, it's just a 230v device I'd have thought? You can hook that up to the mains and it'll charge and discharge separately - it doesn't need to be paralleled with the other battery you
have.

Now, deciding when to charge and discharge is another question. eg you probably don't want battery A to be discharging when battery B is
discharging, otherwise you're just moving energy around (with losses) rather than storing or consuming. But that's something external control systems
(eg Home Assistant) can tell them both what to do.

If your don't have comms between the battery and the inverter, that's where protocols like pylontech come in - there are widgets to translate from
one protocol to another if they don't speak the same. There are also
widgets to translate between EV batteries and domestic inverters[1].

Theo

[1] https://github.com/dalathegreat/Battery-Emulator
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Theo <theom+news@chiark.greenend.org.uk> wrote:

Now, deciding when to charge and discharge is another question. eg you probably don't want battery A to be discharging when battery B is discharging, otherwise you're just moving energy around (with losses) rather than storing or consuming. But that's something external control systems
(eg Home Assistant) can tell them both what to do.

Typo:
"while battery B is *charging*"
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 15/05/2026 12:28, Theo wrote:
of,(the battery at least).

If the battery comes with its own inverter, it's just a 230v device I'd have thought? You can hook that up to the mains and it'll charge and discharge separately - it doesn't need to be paralleled with the other battery you have.

Yes but apart from the extra ~80W overhead of the extra inverter there's
the problem of conflicts between the solar PV hybrid inverter and the AC
one. so under normal circumstances when no solar PV electricity is being exported one can charge the AC coupled battery. . I'm concerned what
happens when there is no solar power and the house is running off
battery. What conflicts might occur? I think the AC coupled battery will discharge first until it shuts down, then the hybrid battery would take
over. As I am not sure I hesitate to do it.

Had the people that installed the hybrid just left the AC coupled unit
alone I might have experimented but as they insisted on decommissioning
it I cannot decide.

Now, deciding when to charge and discharge is another question. eg you probably don't want battery A to be discharging when battery B is discharging, otherwise you're just moving energy around (with losses) rather than storing or consuming. But that's something external control systems
(eg Home Assistant) can tell them both what to do.

Yes as above.

I don't have home assistant as it is too technical and involved for me
to understand.

If your don't have comms between the battery and the inverter, that's where protocols like pylontech come in - there are widgets to translate from
one protocol to another if they don't speak the same. There are also
widgets to translate between EV batteries and domestic inverters[1].

Theo

[1] https://github.com/dalathegreat/Battery-Emulator

Nice find Theo but probably beyond my capabilities.

I had a friend come round and try and sniff the protocols using a Teensy
4.1 Triple CAN Board with 240x240 LCD and Ethernet |u 1 which I bought
for the purpose but it had us both flummoxed.

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

AJH <news@loampitsfarm.co.uk> wrote:

On 15/05/2026 12:28, Theo wrote:
of,(the battery at least).

If the battery comes with its own inverter, it's just a 230v device I'd have
thought? You can hook that up to the mains and it'll charge and discharge separately - it doesn't need to be paralleled with the other battery you have.

Yes but apart from the extra ~80W overhead of the extra inverter there's
the problem of conflicts between the solar PV hybrid inverter and the AC one. so under normal circumstances when no solar PV electricity is being exported one can charge the AC coupled battery. . I'm concerned what
happens when there is no solar power and the house is running off
battery. What conflicts might occur? I think the AC coupled battery will discharge first until it shuts down, then the hybrid battery would take over. As I am not sure I hesitate to do it.

I expect that each inverter has a current transformer around the meter tails
to sense how much current the house is taking and how much is coming
from/going to the grid. To run the house from battery they want to output
just enough to match the loads so that the grid draw is zero, but also
nothing is being exported.

So you can move these CTs around to set how much current the batteries are generating. eg if you put one on the live to the upstairs sockets circuit
and one on the live to the downstairs sockets circuit, each battery would output enough to supply loads on those circuits. (they have a
directionality of current flow, typically marked with an arrow, so make sure they aren't put on backwards, in which case they'll think import is actually export). There is no problem if both inverters are outputting at the same
time - worst case you'll export when you didn't intend to.

You could also have relays to switch between different CTs, eg connect
inverter A to the main house CT and inverter B to a dummy CT with no wires through it, with the result that inverter A will power the house and B will output (roughly) nothing. Then switch them around and inverter B will power the house. That's doable with no messing about with CANbus, and no software
at all if you wish (although a bit of logic in software is always possible,
eg 'if inverter A is no longer outputting [sensed by CT or by the red light
on the front] then switch to inverter B')

Had the people that installed the hybrid just left the AC coupled unit
alone I might have experimented but as they insisted on decommissioning
it I cannot decide.

Assuming there's nothing unsafe about it, I suspect they just weren't interested in trying to make them work together.

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

On 15/05/2026 22:42, Theo wrote:

Assuming there's nothing unsafe about it, I suspect they just weren't interested in trying to make them work together.

I think it was more to do with complying with the DNO, With two
inverters and G100 approval it may have been the extra theoretical
export potential.

I think your logic is probably right though. I shall see about mounting
the inverter and think about where the CTs should go.

Theo I still have your email address from when we met in Haslemere, is
it alright if I contact you ?

Andrew
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Theo wrote:

I expect that each inverter has a current transformer around the meter tails to sense how much current the house is taking and how much is coming from/going to the grid.

Can a CT differentiate between import and export?
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Andy Burns <usenet@andyburns.uk> wrote:

Theo wrote:

I expect that each inverter has a current transformer around the meter tails
to sense how much current the house is taking and how much is coming from/going to the grid.

Can a CT differentiate between import and export?

Yes, the current reverses direction and so does the magnetic field, meaning
the CT output voltage goes negative.

It can only sense the current in the wire it's clamped around though, it doesn't have a 'whole system' view. eg battery outputting on one ring main that's consumed by another would look like export if you put the CT around
the tail of the exporting ring main, even though nothing might pass through
the meter.

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

AJH <news@loampitsfarm.co.uk> wrote:

On 15/05/2026 22:42, Theo wrote:

Assuming there's nothing unsafe about it, I suspect they just weren't interested in trying to make them work together.

I think it was more to do with complying with the DNO, With two
inverters and G100 approval it may have been the extra theoretical
export potential.

Ah, that may be a reason. If you need to have G100 then they probably need assurance that you won't export more than the allowed limit, and a random collection of boxes might not meet the G100 requirements.

I think your logic is probably right though. I shall see about mounting
the inverter and think about where the CTs should go.

Theo I still have your email address from when we met in Haslemere, is
it alright if I contact you ?

Feel free.

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Theo wrote:

Andy Burns <usenet@andyburns.uk> wrote:

Theo wrote:

I expect that each inverter has a current transformer around the meter tails
to sense how much current the house is taking and how much is coming
from/going to the grid.

Can a CT differentiate between import and export?

Yes, the current reverses direction

Other that at 50 Hz ?

and so does the magnetic field, meaning
the CT output voltage goes negative.

It can only sense the current in the wire it's clamped around though, it doesn't have a 'whole system' view. eg battery outputting on one ring main that's consumed by another would look like export if you put the CT around the tail of the exporting ring main, even though nothing might pass through the meter.

Theo

--- Synchronet 3.22a-Linux NewsLink 1.2

From Newsgroup: uk.d-i-y

Andy Burns <usenet@andyburns.uk> wrote:

Theo wrote:

Andy Burns <usenet@andyburns.uk> wrote:

Theo wrote:

I expect that each inverter has a current transformer around the meter tails
to sense how much current the house is taking and how much is coming
from/going to the grid.

Can a CT differentiate between import and export?

Yes, the current reverses direction

Other that at 50 Hz ?

I believe you can tell from the phase shift. A negative current flow in the primary of the CT turns into a 180 degree phase shift of the voltage induced across the secondary.

That does mean you need a reference for mains phase to compare, which the inverter needs anyway.

Theo
--- Synchronet 3.22a-Linux NewsLink 1.2