SolaX Triple 5.8 kWh with SolaX AC inverter to date it has been working fine, the APP is reliable although a bit on the slow side. £4,500 fitted in October 2022. complete with a HIES warranty. SolaX comes with a 10 year warranty which can be extended to 20 years if taken out up to 3 years after registration, we may consider extending the warranty.
We import approximately 3000 kWh, 1800 kWh is used to charge up the PHEV and 1200 kWh for domestic use, the 3000 kWh is charged up Octopus Agile off peak we are wavering between 10/12 pence kWh. We export approximately 3000 kWh @ 15 pence kWh are electric bill is virtually zero.
I realise you situation is totally different to ours, the 5.8 kWh is financially about right for use. 2 x 5.8 kWh battery would probably suit your needs you are probably looking at £6,500 fitted.
Does the Foster include the inverter and fitting ?
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.