Talk me into or out of solar for a renovated 1930s terrace
Trying to work out whether solar is actually financially worth it for our house in the UK, and I would really appreciate some grounded opinions from people who are not salespeople.
We live in a 1930s red brick terrace in South East England with an east/west facing roof. The house is currently under major renovation, and we have already done most of the realistic insulation and efficiency upgrades that are practical for this type of house. It has been fully rewired, loft insulation upgraded, windows improved, and downstairs wet underfloor heating is currently being installed.
The house already feels dramatically better thermally. Upstairs rooms sit around 20–21.5C with very little radiator use, and the house holds heat surprisingly well now.
We have had two solar quotes:
16x LONGi 535W panels
10.24kWh Dyness battery
Solis 6kW hybrid inverter
Quoted generation: 5664 kWh/year
£9640 installed
12x AIKO 465W panels
10kWh Growatt battery
5kW inverter
~£8100
My problem is that the more I research solar, the more it feels like a “lovely to have” rather than an obvious financial decision.
We would likely need finance 6k towards the project(~6% probably), export rates already seem to be falling, battery lifespan worries me relative to payback time, and inverter replacement costs are another factor. We also do not have an EV, and because the house only has on-street parking, it is unlikely we would ever realistically install a home charger.
The irony is that because the house is already becoming much more energy efficient, the solar savings potential also seems lower.
I am struggling to justify another £8–10k financed project during an already expensive renovation when the return seems to be 10+ years away.
Am I being overly cautious here, or is this actually a fairly reasonable conclusion in the current UK market?