The Short Answer
Ofgem's typical home, using 2,500 kWh a year, comes to 6 panels of 430W on an unshaded south-facing roof in the Midlands, and we'd size up if you're planning an electric car or a heat pump. A home with both needs about 18 panels.
To work out yours, find your yearly electricity use on your bill and divide it by what each kWp of panels makes a year where you live: 969 kWh on that Midlands roof, on the European Commission's PVGIS model (other areas below).
Matching your yearly use doesn't mean buying nothing, though. On the government's SAP 10.2 self-use formula, the typical home would use only about 34% of what its 6 panels make, with no battery. The rest is exported, mostly in summer, and you still buy power after dark and in winter.
So we wouldn't stop at your yearly use if the roof takes more. Small systems cost more per kW, and exported power still earns 12p, so in that same home a 4kW system (about 10 panels) pays back in about 11 years on the calculator's figures, against about 12 for 6 panels. That's why our cost and worth-it guides work on 4kW.
Work Out Your Number
Solar panel calculator
How many solar panels do you need?
Uses the European Commission's PVGIS solar model for your region and roof direction, not a single UK average.
On your bill or annual statement. Ofgem's typical home uses 2,500kWh.
Planning to add
Car: 7,100 miles a year at 3.3 miles per kWh (EV Database). Heat pump: 9,500kWh of heat at a SCOP of 3.5.
Which way does the roof face?
East and west roofs often split the panels across both sides, which suits a home that uses power morning and evening.
Panel size
Each panel is about 1.72m by 1.13m.
You need
6 panels
A 2.58kWp system, about 12 square metres of roof, making around 2,500kWh a year, enough to match your yearly use of 2,500kWh.
969
kWh per kWp a year here
£5,000
typical cost, 0% VAT
£421/yr
bill saving plus export
12 years
to pay for itself
Making as much as you use isn't the same as not buying any. Without a battery, on the government's SAP 10.2 self-use formula this home would use about 34% of its solar as it's made; the rest goes to the grid at the export rate and you still buy power after dark.
Yield: PVGIS v5.2, 35 degree pitch, 14% system losses, unshaded. Value: 34% used at home (the government's SAP 10.2 self-use formula for this system and your yearly use) at 26.32p, the rest exported at 12p (Outgoing Octopus, for Octopus supply customers on eligible tariffs). Cost at DESNZ's 2025/26 mean for home installs: £1,955 per kWp under 4kW, £1,645 from 4kW. Shading, pitch and your own tariff will move these numbers.
Typical Sizes
| Home | Electricity a year | 430W panels | System | Roof space | Cost (DESNZ home mean) |
|---|---|---|---|---|---|
| Ofgem's typical home | 2,500 kWh | 6 | 2.58kWp | about 12 square metres | £5,000 |
| Typical home plus an electric car | 4,700 kWh | 12 | 5.16kWp | about 23 square metres | £8,500 |
| Typical home plus a heat pump | 5,200 kWh | 13 | 5.59kWp | about 25 square metres | £9,200 |
| Typical home plus both | 7,400 kWh | 18 | 7.74kWp | about 35 square metres | £12,700 |
Where the figures come from: Ofgem's typical consumption figure for a home; the car at DfT's average of 7,100 miles a year and EV Database's 3.3 miles per kWh (about 2,200 kWh); the heat pump heating a 3-bed (9,500 kWh of heat, from DESNZ's measured gas use) at a SCOP of 3.5 (about 2,700 kWh). Costs are at DESNZ's mean for home installs, which is higher per kW below 4kW, with 0% VAT until 31 March 2027. A heat pump uses most in winter, when panels make least, so solar covers only part of it.
Where You Live and Which Way the Roof Faces
The European Commission's PVGIS model gives these yearly kWh for each kWp at a 35 degree pitch with 14% system losses. The sizes above use the Midlands south figure; our savings figures elsewhere use a rounder 950.
| Area | South | South-east or south-west | East or west | North |
|---|---|---|---|---|
| South West England (Plymouth) | 1,098 | 1,037 | 870 | 571 |
| London and South East | 1,025 | 955 | 796 | 547 |
| South Wales (Cardiff) | 1,029 | 977 | 822 | 538 |
| Midlands (Birmingham) | 969 | 904 | 757 | 526 |
| North West England (Manchester) | 886 | 831 | 704 | 497 |
| Northern Ireland (Belfast) | 918 | 861 | 722 | 499 |
| Central Scotland (Edinburgh) | 915 | 855 | 709 | 478 |
| Highlands (Inverness) | 806 | 758 | 641 | 450 |
In the Midlands, east or west gives up about 22% against south and north about 46%, so direction matters more than whether you live in Plymouth or Manchester. With an east and west roof, we'd consider panels on both sides, which spreads the output across the day.
Will It Fit on Your Roof?
A typical 430W panel is about 1.72m by 1.13m; that's about 1.95 square metres each, which is what the table and calculator use, so leave a little extra for gaps and edges. Measure the roof face you'd use, take off chimneys, roof windows and vents, and divide by 2 to be safe. If the roof won't take enough, put the number in the calculator above and it'll tell you what share of your use it covers.
Shade
Trees, chimneys, dormers and next door all cut output, and a low winter sun makes shadows longer. On a simple string inverter, a shaded panel holds back the others on its string; optimisers or microinverters let each panel work on its own, which is worth it on a partly shaded roof. Ask the installer for the shading assessment behind their generation estimate. Our inverter types guide covers the choice.
Over 3.68kW: Network Approval
Small systems connect under the network rule known as G98, which covers generators up to 16A per phase, about 3.68kW on a normal single-phase supply. Anything bigger needs the network operator's approval first (G99), which can take weeks. The installer applies. Some fit a 3.68kW inverter to a bigger array to stay under G98, so check which your quote assumes.
Planning Permission
In England, panels on a house are usually permitted development. The Planning Portal's limits include no higher than the highest part of a pitched roof (excluding the chimney), no more than 200mm proud of the roof slope, and none on a building in the grounds of a listed building. In a conservation area or World Heritage Site, panels can't go on a wall facing a highway. The rules changed on 27 August 2026 and you can use either the old or new rules until 27 August 2027. Wales, Scotland and Northern Ireland have their own rules, so check with your council. Leaseholders may need the freeholder's permission.
What You Don't Need
- Premium high-efficiency panels, in our view, unless the roof is short of space. Their selling point is more watts per square metre, which only matters when you run out of roof.
- A battery just because the system is big. Our battery guide runs the numbers.
Next: what solar costs and whether it's worth it.
Get your system sized by an installer
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