After twelve months, Andrew Till of Mr. EV has a complete set of numbers from his solar and battery installation. The setup is 30 solar panels on an east-west facing roof, combined capacity 13.5 kW, paired with two Alpha batteries totalling 20 kWh of storage. Total system cost was £18,990. Over the year, the household paid £2,530 for electricity, earned £1,015 by exporting surplus power to the grid, and saved £2,969 by using solar and stored power rather than drawing from the grid at peak rates. Combined savings and export income come to £2,983 for the year, putting the payback period at 6.4 years on the original system cost.
The headline figure has important context. The house runs on electric radiators, one of the least efficient forms of electric heating. A heat pump would reduce energy use substantially, improving the solar and battery economics further. Two electric vehicles are also charged on-site, almost entirely at the off-peak rate. The system is configured so the cars and the home draw from separate parts of the setup: the household uses battery power stored overnight, while the EVs charge overnight without competing for that same reserve. Over approximately eleven months, both vehicles consumed 2,877 kWh at a cost of around £201. Without the solar and battery installation, the estimated annual electricity bill would have been around £4,500.
The payback calculation required a spreadsheet rather than the Alpha battery app, which over-reports savings when two inverters are linked in parallel. A software fix is in development but hasn't reached the UK yet. Adjusting for that, the net electricity cost for the year came to £1,516 after subtracting export income. The 6.4-year payback already beats the 7 to 8 years Heatable projected at installation. One complication arose in April: a settings change caused the inverters to suppress generation for several weeks, losing meaningful export income before the problem was identified. The electric radiators also cause occasional brief draws from the grid during the day because their power spikes are faster than the battery inverter can respond to.
Bottom line: A 6.4-year payback on a system that also reduces grid exposure, adds to house value, and currently carries 0 percent VAT (through March 2027) makes a reasonable case. The exact number will shift with future electricity pricing, but the direction is broadly right for a household that's prepared to manage the system actively.