The short answer: most UK homes fit a system of between 3 kW and 6 kW, costing from about £5,000 to £11,000 installed. Bigger systems cost more in total but less for each kilowatt.
Cost, panels and output by size
| System size | Panels | Installed cost | Cost per kW | Typical yearly output |
|---|---|---|---|---|
| 3 kW | 8 | £5,000 to £6,000 | £1,670 to £2,000 | 2,550 kWh |
| 4 kW | 10 | £6,000 to £8,000 | £1,500 to £2,000 | 3,400 kWh |
| 5 kW | 13 | £7,000 to £9,000 | £1,400 to £1,800 | 4,250 kWh |
| 6 kW | 15 | £8,000 to £11,000 | £1,330 to £1,830 | 5,100 kWh |
Panel numbers assume 400 W panels. Output assumes a south-facing, unshaded roof and a typical UK figure of 850 kWh a year for each kW.
For comparison, government data puts the median price for systems up to 4 kW at £1,595 per kW in 2025/26.
Why bigger systems cost less per kW
Scaffolding, the inverter, the electrical work and the installer's time on site cost much the same whether you fit eight panels or fifteen. Only the panels and mounting kit grow with the system. That is why the step from 4 kW to 6 kW is usually the cheapest capacity you can buy.
Which size suits which home
| Your home | Yearly electricity use | Size to consider |
|---|---|---|
| Small home, low use | Under 2,000 kWh | 3 kW |
| Typical three-bedroom home | About 2,500 to 3,500 kWh | 4 kW |
| Larger home or higher use | 3,500 to 4,500 kWh | 5 kW |
| Electric car or heat pump, now or planned | Over 4,500 kWh | 6 kW or more |
Your roof may decide for you. A 4 kW system needs roughly 20 to 24 square metres.
Should you fill the roof?
Often, yes. Extra panels are cheap once the installer is on the roof, and spare power is sold to the grid. On a good export tariff of around 15p per kWh, extra panels still pay for themselves. On a poor tariff they take much longer, so check your export rate first. See Smart Export Guarantee rates.
Larger systems can need approval from your network operator before installation. Your installer handles this.
Solar cost calculator UK edition
What would solar cost, and what would it be worth to you?
Six questions. No email address, no phone number. You get a size, a price range, a yearly figure and a payback range, with every assumption shown underneath.
Question 1 of 6
Your estimate
This is an estimate for general information, not a quote. It was correct at the time of publication and uses the assumptions shown. The performance of solar PV systems is impossible to predict with certainty, because sunlight varies from place to place and year to year. Only a survey by a certified installer can give you an accurate design and price. This is not financial advice.
Your answers go with you in this browser tab only, so the quote form does not ask again.
How we worked this out
| Assumption | Value | Source |
|---|---|---|
| Installed cost | 3 kW solar: £5,000–£6,000; 4 kW solar: £6,000–£8,000; 5 kW solar: £7,000–£9,000; 6 kW solar: £8,000–£11,000; 5 kWh battery: £2,500–£5,000; 10 kWh battery: £4,500–£8,000 | Published UK price guides, government installation cost data (2025/26) and MCS installation costs (2025) |
| Electricity price | 26.32p per kWh | Ofgem price cap, Direct Debit, October to December 2026 |
| Export rate | 15p per kWh | Which? fixed export tariff comparison, April 2026 |
| Output per kW | 850 kWh per year for a south-facing roof | National estimate used by this calculator: a 4 kW system generating 3,400 kWh per year |
| Roof direction factors | South: 100%; South-east: 95%; South-west: 95%; East: 82%; West: 82%; North-east: 67%; North-west: 67%; North: 55%; Flat roof: 90%; Not sure: 82% | Published UK output tables; indicative factors used by this calculator |
| Shade factors | No shade: 100%; Some shade: 90%; Heavy shade: 75% | Calculator estimates; an MCS installer measures shade on site |
| How home use is estimated | Home use of solar power is estimated using an approximation based on MCS 032 | |
See also the cost to install solar panels and solar and battery costs.
Sources
Correct at the time of publication, 14 November 2026.
- Department for Energy Security and Net Zero, solar PV cost data: https://www.gov.uk/government/statistics/solar-pv-cost-data
- MCS, solar panels: costs and considerations: https://mcscertified.com/consumers/technologies/solar-photovoltaic-pv/
- Price ranges are drawn from published UK price guides. Cost per kW and output figures are our own calculations.