FoxESS Community - Owners & Installers Forum

Hi all,

I'm looking to get a new solar PV but not too sure on what size to go. We're in Worcestershire, UK in a 5 bedroom detached house. We're 2 adults and 2 young kids and someone is generally home most the time.

We're looking at a 6.51kw solar system (we can only fit about 14 panels on our roof due to it having a few velux windows in the way).

I've got 2 quotes from the supplier we're thinking of using with different sizes invertor and batteries.

We use approx 6000kwh annually on Octopus IOG, about 1500-2000 of that is for our EV. We don't currently have a heat pump but we're considering it in 3-5 years.

Both quotes have the same 14 aiko panels and then:

Quote 1 has a KH7 (7kw) invertor and 1x EP12 (11.5kw) battery.

Quote 2 has a KH 10 (10kw) invertor and 2x EP12 batteries (23kw)

There is about £2600 difference between the 2 quotes.

Question is I guess. Is it worth the extra for the higher kw invertor and more batteries or should I stick with the 1 EP12?

Any help or advice would be great. Thanks

I would go with the extra battery personally, a heat pump will around 3x less kWh than the gas use. (rule of thumb)
So 18,000 kWh of gas would give 6,000kWh of electric, and the single EP12 would struggle.

The 2nd EP12 would allow you to purchase/store solar for lowest household running costs.
Once you get a heatpump, then you may have to switch to Octopus Cosy for Winter.

At such a small price difference i’d go with the bigger system as well, it’ll give you more usable power in the home (pesak 10 vs 7kw) and having more batteries will increase their life and make your life better as you won’t suffer from temperature problems as much in a cold winter plus that extra capacity will help on the few days where you need that bit more.

Make sure the installer wires the system so that it cannot see the EV usage or you’ll be charging the car with your home batteries.