A typical 4.5kWp solar system costs about £7,600 in 2026. Here is what 3kW, 4kW, 5kW and 6kW systems typically cost, make and save, and what each will cost once VAT returns in April 2027.
The short answer
A typical 4.5kWp home system costs about £7,600 to install, according to the Energy Saving Trust. Smaller systems cost less in total and larger ones more. Here is roughly what each common size costs, makes and saves in 2026, and what it will cost once VAT returns.
Costs by system size
The table scales the Energy Saving Trust’s £7,600 for 4.5kWp in a straight line to other sizes. In practice larger systems often cost a little less per kWp, and real quotes vary with your roof, the equipment and where you live, so treat these figures as a guide. The VAT column shows what the same system would cost once the 0% rate ends on 31 March 2027.
System size | Panels (about) | Typical cost now | Same system with 5% VAT | Electricity a year | Typical saving a year |
|---|---|---|---|---|---|
3kWp | 8 | £5,070 | £5,320 | 2,500 kWh | £240 to £450 |
4kWp | 10 | £6,760 | £7,090 | 3,400 kWh | £280 to £580 |
4.5kWp | 12 | £7,600 | £7,980 | 3,800 kWh | £310 to £650 |
5kWp | 13 | £8,440 | £8,870 | 4,200 kWh | £330 to £710 |
6kWp | 15 | £10,130 | £10,640 | 5,000 kWh | £370 to £840 |
How we worked it out:
- Electricity made: about 840kWh a year for each kWp, the government’s median for 2023/24. In 2024/25, the least sunny year since 2012/13, it was about 806kWh. Homes further south usually make more.
- Share used at home: the MCS tables for a home using 2,500 to 2,999kWh a year with someone in about half the day, no battery. That is about 15% to 25% depending on system size, because a bigger system makes more than the home can use at the time.
- Prices: electricity you use saves 26.32p per kWh (the October to December 2026 price cap). Exported electricity earns about 4p per kWh on tariffs open to anyone, and up to about 15p from some suppliers if you also buy your electricity from them.
You can change these assumptions in our solar savings calculator.
A worked example: 4kWp vs 6kWp
Take a home that has room for either system. A 4kWp system costs about £6,760 and makes about 3,400kWh a year. A 6kWp system costs about £10,130, roughly £3,370 more, and makes about 5,000kWh a year.
Without a battery, most of the extra electricity from the bigger system is exported rather than used, so its extra value depends heavily on your export rate. At 4p per kWh the bigger system adds about £90 a year; at 15p it adds about £260. That is why a good export tariff, or a battery, matters more as systems get bigger.
Which size do you need?
Start from your yearly electricity use, which is on your annual statement. Dividing it by about 840 gives a rough system size that would make as much electricity as you use in a year. Ofgem’s typical home uses 2,500kWh, which works out at about 3kWp. Many homes fit more if the roof allows, especially if an electric car or heat pump is planned. Our guide to how many solar panels you need goes into more detail.
What else affects the price
- A battery: about £4,600 for a 5kWh battery (Energy Saving Trust), and fitting it with the panels usually saves on installation costs.
- Your roof: awkward shapes, height and access add time and scaffolding.
- Equipment: the panels, the inverter, and any extra equipment for shaded roofs.
- Connection: larger systems need permission from the electricity network before they are connected, which can add time.
Prices have been falling
Which?, using government figures built from the official MCS installation records, reports that the cost of small systems (up to 4kW) fell by 7% between 2024/25 and 2025/26. Getting more than one quote is the best way to know you are paying a fair price: see our checklist for comparing quotes.
What to do next
For a price for your own roof, get free solar quotes from an installer who covers your area. It’s free and there’s no obligation.
Sources
- Energy Saving Trust: Solar panels (updated 1 Oct 2026)
- Energy Saving Trust: Solar panel battery storage (6 Oct 2026)
- GOV.UK: Solar PV cost data (28 May 2026)
- Ofgem: Energy price cap rates (Oct 2026)
- Which?: The best and worst SEG tariffs (24 Apr 2026)
- GOV.UK: Extension of VAT energy-saving materials relief (11 Jan 2024)
- Ofgem: Summary of changes to the price cap (typical consumption values) (June 2026)
- DESNZ: Feed-in Tariff load factor analysis 2024/25 (18 Dec 2025)
- MCS: Self-consumption guidance (MGD 003), lookup tables 9-12 (1 Aug 2019)
- Which?: Solar panel costs (updated 3 Aug 2026)