A further update. After 3 months the batteries have cut the bought in power by 25%. This means a just under 12 year payback based on the part of the year with least sunshine. Despite that we have seen days with nearly no bought in power.
Today after a few sunny days we started on battery power and have bought in 360 kWh vs a usage of 11 KWh. The payback so far is under 12 years and I'm sure will get below 6 easily over a full year.
In addition to increasing electricity costs, another factor that's reducing the time to breakeven is capital depreciation. We were earning bugger all interest from the money we used to buy our solar setup, and if we'd left it in the bank it would now be worth at least 10% less. In the last year our setup has provided us with over £1200 worth of electricity. Based on my model of future inflation I reckon payback will be in 8 years for my setup, which is fine by me.
Tim H. 1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE
