Second PV system?

[Robfitz]

I’ve had solar PV on the south facing part of my roof since 2014 and get paid under the FIT scheme. Current system generates 4300-4400kwh a year on average. My immediate plan is to add an AC coupled inverter and battery to the existing system in the next couple of months.

Is it possible to add a second entirely separate PV system on the east/west facing parts of the roof without it interfering with the FIT on the existing system? I don’t want to touch the existing one and mess up the FIT but have space for another 12-14 panels. If I added the second PV system next year could it use a hybrid inverter with another battery directly attached?

I know it would need approvals but see a number of you have much larger installs so presume the DNO are open to this in theory?

[Joeboy]

Short answer is yes you can. The established route is second system T'd into your battery system dc-dc. That would be after you seek approval from dno for the battery system install & ac coupled hybrid inverter as they will be a part of your FIT circuit.

[Stinsy]

Yes you can do that. A few points:

- So long as the new system doesn't go through your FiT meter then it doesn't affect FiT payments. (Technically you are permitted to add to a FiT array and have it go through the meter but you have to account for the extra capacity proportionally and this is rarely advantageous).
- You'll need DNO permission for the additional inverter capacity. (I assume you have 4kWp of panels on a 3.6kW inverter currently).
- You might as well fit an additional hybrid inverter now, you can then add batteries/solar in whatever order you like.

[Robfitz]

Thank you both.

I was thinking I’d end up with 3 inverters and 2 separate battery systems: original PV inverter in the loft, ac inverter and battery in the downstairs cupboard with the generation meter for that PV system and then the hybrid inverter for the second PV with an additional battery attached directly in the loft.

From what you are saying I could do it with just 2 inverters if I fit a hybrid one now, though I presume I’d want that to be in the loft to be proximate to the panels and then fit the batteries up there? Guess that is just extra wiring back from the downstairs cupboard upto the loft. It may make sense to do it at once and save the vat on the inverter and battery.

Had a quick search on gov.uk and it suggested the Generation part of the FIT payment could continue unchanged but would need to opt out of the deemed export element and would then get combined export payment from both systems under the SEG scheme for what is actually exported if I understand correctly?

[nowty]

Had a quick search on gov.uk and it suggested the Generation part of the FIT payment could continue unchanged but would need to opt out of the deemed export element and would then get combined export payment from both systems under the SEG scheme for what is actually exported if I understand correctly?

Only if you really want to opt out of deemed FIT exports which is guaranteed and RPI uplifted. Once you've opted out there is no going back and SEG only guarantees the amount you get will be more than zero. For me its not worth it as I self use 90% of what I generate.

[Robfitz]

Ok so I could leave the existing one completely as is. Second system would be SEG?

[nowty]

Ok so I could leave the existing one completely as is. Second system would be SEG?

No, you cannot get FIT export payments and SEG together. You have to make the choice depending on your circumstances, I am just making the point that it might not necessarily be the right decision.

[Robfitz]

Ok understood - thanks.

[Stinsy]

You definitely don’t want to opt out of deemed export on your FiT if you can help it! With batteries your export will be teeny but you’ll be paid for 50%. It is free money!

You should focus on self-consumption. Batteries are best, but if you have 8kWp of solar you’ll need a diverter on your DHW tank and a suitable BEV charging point as well if you stand a hope of using what you generate in August!

[Robfitz]

Have a solar I boost on the immersion heater that recently died and looking at an Eddi to replace it. EV probably a couple of years off but is the plan.

Was thinking this would broaden the generation over the year rather than just the peak and if going to spend the money now don’t want to end up making the wrong decision.