A Northampton family who wanted the most roof for the money
Laurence owns a family home in Northampton with a roof that could carry a lot of panels. What he asked for was not the biggest possible system, nor the cheapest. It was the best ratio: maximum output from the usable roof, at a price that made the payback period short, with a battery properly matched to the array rather than bolted on.
Get the panel-to-cost ratio right
It is easy to make a system look good by spending more. Add panels, add storage, and the generation figure climbs while the payback quietly stretches out. It is also easy to go the other way and fit a small array that pays back fast but never moves the bill much. The roof here comfortably carried twenty-three panels, so the design question was how much storage to put behind them before the extra cost stopped earning its keep.
Twenty-three all-black panels and 18 kWh behind them
We fitted twenty-three Aiko 475W all-black modules, 10.93 kWp, sized to the full usable roof, with a SigenStor EC 10.0SP hybrid inverter and two SigenStor BAT 10.0 batteries giving 18 kWh of usable storage. That is enough for round-the-clock self-supply without paying for capacity that would sit idle. Bird mesh went on all the pitched-roof panels, and the all-black modules were chosen for how the roof looks as well as what it makes. Survey to commissioning, £14,900.
- 23 × Aiko 475W solar panels (10.93 kWp total)
- SigenStor EC 10.0SP hybrid inverter
- 2 × SigenStor BAT 10.0, 18 kWh usable storage
- All-black modules chosen for kerb appeal as well as output
- Bird mesh fitted to all pitched-roof panels
Over 10,000 kWh a year, paid back in about eight
The system generates about 10,060 kWh a year and roughly 65% of it is used in the house. That is around £1,860 a year, about £155 a month, and in the region of £46,000 across 25 years. At £14,900 installed, the system pays for itself in about eight years, one of the shorter paybacks of the homes on this site, which is exactly what Laurence asked for.
Generation and saving figures on this page are estimates, modelled from the system size and a typical UK yield for the location. They are not meter readings. Generation is system size in kWp multiplied by regional specific yield. Savings count self-consumed units at the 24.67p/kWh Ofgem residential rate and exported units at 7p/kWh, over 25 years with no tariff rises applied. Carbon uses 0.21 kg CO₂ per kWh displaced, and trees are illustrative only. Your own numbers depend on your roof, your consumption and your tariff at the time of install.
