PV back on the table?

[Tinbum]

I've put my Growatts up for sale but, to be honest, I'd be quite happy to keep them as they have been really good. I'm slowly working on the RS485 communication to see if I can figure it out. The batteries don't power up unless they have communication with their current BMS. I can see the communication but I'm still trying to learn about how Modbus RS485 RTU protocol works.

[Paul_F]

Fag-packet maths here - this is taken from our planned new-build which we've just asked the architects to submit for planning permission:

• 15.5kW of panels on a SW/NE alignment - cost of panels + GSE trays + inverter is ~£10k at Midsummer Wholesale.
• Covers ~73m² of roof area - cost saving from not needing tiles or slates @ £30/m2 is ~£2k. This should roughly balance out the additional wiring and installation costs given that scaffolding will already be there and first fix wiring is happening anyway.
• Output is 12.7 MWh/year. Value is between 5-25p/kWh (depending on assumptions about self-consumption, electric cars, home battery, wholesale prices, etc.) - £635 to £3175 value.
• Working assumption for our situation is ~15p/kWh on average - this gives payback of about 7 years.

Batteries don't work for us given the normal price of hybrid systems + batteries in the UK. There are hybrid inverters out there which are cost effective for us (e.g. this Sungrow one) - unfortunately 3-phase inverters aren't really very common over here so we'd probably need to import it ourselves. If so I might be very tempted to take a gamble on buying some LiFePO₄ battery sets (not just the cells) on Alibaba although almost certainly not as part of the build.

[Tinbum]

Remember for new build in the UK you get the VAT back on most things- not white goods (which they are very keen on).

[AE-NMidlands]

For retro-fits is it right/correct that you get a battery at a lower rate of VAT, a solar alone at the full rate, but all of a solar-with-battery at the reduced rate? (except the labour, of course)
A

[Stinsy]

For retro-fits is it right/correct that you get a battery at a lower rate of VAT, a solar alone at the full rate, but all of a solar-with-battery at the reduced rate? (except the labour, of course)
A

Correct. Batteries are 5% if bought att he same time as solar installation. 20% all other times...

[Paul_F]

Remember for new build in the UK you get the VAT back on most things- not white goods (which they are very keen on).

I've not forgotten - those prices are ex-VAT. Worth clarifying for others though...