Solar panel calculator
How much a home solar system would generate where you live, what it could save and roughly how long it takes to pay back. No sign-up, no installer leads.
Solar output across the UK
Estimated yearly output per kWp, by postcode area, from the European Commission’s PVGIS model:
| Area | South, 35° | East/west | 4 kWp south: kWh a year | Value a year* |
|---|---|---|---|---|
| London (E) | 1020 | 818 | 4,080 | £782 |
| Plymouth (PL) | 1108 | 869 | 4,432 | £849 |
| Cardiff (CF) | 1042 | 809 | 4,168 | £799 |
| Birmingham (B) | 966 | 774 | 3,864 | £740 |
| Norwich (NR) | 1041 | 826 | 4,164 | £798 |
| Manchester (M) | 886 | 717 | 3,544 | £679 |
| Belfast (BT) | 919 | 728 | 3,676 | £704 |
| Newcastle (NE) | 950 | 738 | 3,800 | £728 |
| Edinburgh (EH) | 904 | 706 | 3,616 | £693 |
| Aberdeen (AB) | 916 | 702 | 3,664 | £702 |
*With 50% used at home at 26.32p per kWh and the rest exported at 12p.
These are modelled figures for a clear, unshaded roof. Across all real UK systems, government statistics put average output at about 805 kWh per kW in 2024, a dull year, and about 970 in 2025, the sunniest on record. See our home solar guide and the kilowatt-peak glossary entry.
How the calculator works
- Generation = system size (kWp) × PVGIS yearly yield for your postcode area and roof direction.
- Bill savings = generation × share used at home × your electricity price.
- Export income = the rest × your Smart Export Guarantee rate.
- Payback = system cost ÷ (savings + export income).
Using more of your own power raises the savings, because a kWh you use is worth the full unit rate while an exported kWh earns much less. A home battery or running appliances in the middle of the day helps. The default price is the Ofgem price cap for 1 October to 31 December 2026; the default export rate of 12p is the Energy Saving Trust’s “typical” figure; the default cost is the 2025/26 median from government MCS data.
Frequently asked questions
How much electricity do solar panels produce in the UK?
By the PVGIS model, from about 770 kWh a year per kWp of south-facing panels in Shetland to about 1,150 on the south coast of England, at a 35° tilt. A typical 4 kWp home system in London produces about 4,080 kWh a year by the PVGIS estimate. Real systems often produce less because of shading, dirt and less-than-ideal roofs.
Do solar panels work facing east or west?
Yes. By the PVGIS model, east- or west-facing panels at a 35° pitch produce about 18–24% less than south-facing ones in the UK, spread more evenly across the morning or afternoon. The calculator shows the figure for your area.
How much do solar panels save?
It depends on how much of the electricity you use yourself. Each kWh you use saves you the full unit rate (26.32p at the current price cap); each kWh you export earns the Smart Export Guarantee rate, which varies by supplier. The Energy Saving Trust says export typically pays around 12p a unit.
What does a solar panel system cost?
Government data from MCS-certified installations in 2025/26 shows a median of £1,595 per kW for systems up to 4 kW, so roughly £6,380 for 4 kWp. Quotes vary with roof, scaffolding and batteries.
What is the payback period?
System cost divided by yearly savings and export income. It ignores panel degradation, price changes and maintenance, such as replacing the inverter, so treat it as a rough guide.
General information, not financial advice; get several quotes from MCS-certified installers. Sources: PVGIS (European Commission JRC), DESNZ solar PV cost data, Energy Saving Trust, Ofgem.