Interesting figures. Here are the figures I got for comparison (3kW PV, 4.8kWh battery, SSW facing panels, NE of London.

We used 277 kWh, which would have cost us £77 (including £13 standing charge) We paid: £20 (including £13 standing charge) Solar gave us about 70% We sold back 229 kWh at £34.40 (£0.15/kWh fixed rate)

Total cost for the month was £-13.72, although we're waiting for some figures to come through from our supplier which could knock that down a bit more.

Like you, we use gas for heating and hot water, but when electricity prices are low I use that to heat some water. Gas cost for the month was £11.51 of which £8.52 was standing charge.