The system
10.45 kWp across an east/west roof, a hybrid inverter and 15.06 kWh of storage. £11,999 fully installed. The quote was for 21 panels, but the installers found room for a 22nd on the day, so we got an extra 475W at no cost.
| Panels | 22 × Aiko 475W N-type ABC, all-black, east/west split roof |
| Array | 10.45 kWp · east group azimuth 98° tilt 30°, west group azimuth 278° tilt 32° · ~11.5% annual shading loss per survey |
| Inverter | Sigenergy EC 8.0 SP, an 8 kW hybrid with built-in EMS and Modbus TCP over the LAN. The installer fitted a 6 kW EC 6.0 SP by mistake at first, and it was later swapped for the right unit. The full story → |
| Battery | SigenStor BAT 6.0 + BAT 10.0 = 15.06 kWh LiFePO₄ nominal, 14.60 kWh usable, 10,000-cycle rated. Combined continuous ~7.6 kW, capped by the inverter at 8 kW. |
| Metering | Sigenergy's own plant meters, logged into Home Assistant every 10 seconds |
| Installed | 4 June 2026 |
| Est. generation | ~7,500 kWh/yr before losses (modelled). Real output is running ahead of that. |
| Total cost | £11,999 fully installed, VAT at 0%. That's £1,148 per kWp including the battery |
| Grid connection | G99 approved with no export limit. Certification cleared and export has been paid since 22 September 2026. |
| Tariff | Intelligent Octopus Go import with Outgoing Octopus flat 12p export. Why this tariff → |
| Quoted payback | ~5.4 years on the proposal's model. Tracked daily → |
Warranties, in plain terms
Aiko panel product warranty
Panel performance, ≥87% output
Sigenergy inverter
Battery, or 10,000 cycles
East/west works better than you might think. Peak output is lower than a south-facing array would give, but generation is spread over more of the day, with morning sun on the east face and evening sun on the west. With a battery and time-of-use pricing that suits us. Output lines up better with when we use power, and there's less clipping against the inverter's limit at midday.
The original business case
The pre-install modelling, based on our real smart meter data (we use about 3,667 kWh a year), put year one at £2,029 against the £11,999 cost, with payback in about five and a half years. This site checks that projection against real data every day, on the stats page.
| Revenue stream | Year 1 | How |
|---|---|---|
| Self-consumption | £750 | ~2,800 kWh self-used at a blended avoided rate around 27p |
| Solar export | £465 | ~3,880 kWh of surplus at flat 12p, paid since 22 September 2026 |
| Battery peak-shifting | £260 | Discharge 4–7pm to dodge the evening peak |
| Cheap-slot charging | £120 | Charge in the cheapest overnight half-hours |
| Axle VPP events | £150 | £1/kWh grid-stress dispatches |
| Saving Sessions | £120 | Auto-join and force discharge, November to March only |
| Weather optimisation | £89 | Solcast-driven charge planning via Predbat |
| Load shifting | £75 | Appliances run on solar surplus |
| Total | £2,029 | Payback ~5.4 years |
Projections assume 4% energy inflation and 5% system losses. They're the forecast, and the stats page shows what actually happened.