Key Takeaways
- Cost: a 4kW home system averages about £6,600–£7,800 installed (DESNZ cost data, 2025/26 mean £1,645–£1,955 per kW), with 0% VAT until 31 March 2027.
- Output: 4kW facing south makes roughly 3,500–4,300 kWh a year depending on location — about 3,540 in Manchester, 3,870 in Birmingham, 4,260 in Truro (PVGIS).
- Value: at October–December 2026 price-cap rates, roughly £630–£760 a year without a battery if you use 40% of the output and export the rest at 12p/kWh.
- Payback: about 9–12 years on those assumptions — shorter if you use more of the output yourself or get a keener price, longer on a shaded or north-facing roof.
- Export rates vary from 3p to 18p/kWh depending on supplier and whether you buy your electricity from them. There is no government-set rate.
- Funded solar is rare. This guide is about paying or financing a system yourself.
Updated 23 September 2026: costs moved to the government's 2025/26 solar cost series, savings re-worked at the October 2026 price cap (electricity now carries 0% VAT until March 2027), export rates re-checked with suppliers, and a city-by-city payback table added. Earlier versions of this page quoted national averages that no longer hold.
The real cost in 2026
The most reliable benchmark is the government's own series. Across domestic solar installations registered with MCS between April 2025 and March 2026, the mean installed cost was £1,955 per kW for systems up to 4kW and £1,645 per kW for 4–10kW, VAT included and batteries excluded (DESNZ Solar PV cost data, updated 28 May 2026).
| System | Typical installed price | Best for |
|---|---|---|
| 3kW | £4,900–£5,900 | Terraces, lower electricity use |
| 4kW | £6,600–£7,800 | Typical 3-bed semi |
| 6kW | £9,900–£11,700 | Larger homes, EV or heat pump |
Each size priced between the two DESNZ band averages. Scaffolding, roof type and inverter choice move individual quotes; see solar panel costs for what drives the price. Solar panels and batteries installed in homes are zero-rated for VAT until 31 March 2027, returning to 5% from 1 April 2027 (HMRC Notice 708/6).
How much will you save?
Solar pays you in two ways: every unit you use replaces a unit you would have bought at the price-cap rate, and every unit you export earns your export tariff. From 1 October to 31 December 2026 the GB average price-cap electricity rate is 26.32p/kWh — with no VAT on domestic electricity until 31 March 2027 (Ofgem). A unit used is worth roughly twice a unit exported, which is why how much you use yourself matters more than anything else.
Without a battery, a household out at work during the day might use around 40% of what it generates; a battery can push that to around 70%. Those are planning assumptions, not measurements — your installer's MCS estimate and your own usage pattern are what count.
City by city: a 4kW system at October 2026 prices
| Area | Output per kW (south) | Regional unit rate | Value, no battery | Value, with battery | Payback, no battery |
|---|---|---|---|---|---|
| Cornwall (Truro) | 1,066 kWh | 26.58p | £760 | £950 | 8.7–10.3 years |
| Bristol | 1,023 kWh | 26.58p | £730 | £910 | 9.0–10.7 years |
| Doncaster | 975 kWh | 25.60p | £680 | £840 | 9.7–11.5 years |
| Nottingham | 970 kWh | 25.36p | £670 | £830 | 9.8–11.6 years |
| Birmingham | 968 kWh | 25.60p | £680 | £830 | 9.7–11.6 years |
| Newcastle | 948 kWh | 25.46p | £660 | £810 | 10.0–11.9 years |
| Sheffield | 947 kWh | 25.60p | £660 | £820 | 10.0–11.8 years |
| Manchester | 886 kWh | 26.49p | £630 | £780 | 10.4–12.4 years |
Output: PVGIS 5.3, 35° south-facing, 14% losses. Value: 40% (no battery) or 70% (with battery) used at the regional October–December 2026 price-cap unit rate, the rest exported at 12p/kWh. Payback: DESNZ price range for 4kW (£6,600–£7,800) divided by the no-battery value; the battery's own cost is not included. Each area links to its local guide with planning, housing and grid details.
Smart Export Guarantee: what you're paid for exports
Under the Smart Export Guarantee, suppliers with 150,000 or more domestic customers must offer an export tariff, and the rate must always be above zero — but suppliers set the rate, and you can choose any SEG supplier, not just the one you buy from (Ofgem). You need an MCS-certified installation and a smart or export meter.
| Supplier | Tariff | Rate | Who can get it |
|---|---|---|---|
| Octopus Energy | Outgoing Octopus | 12p variable | Octopus import customers on eligible tariffs |
| E.ON Next | Next Export Exclusive | 13p, 12-month fixed | E.ON Next import customers |
| E.ON Next | Next Flex Export | 6p variable | Anyone |
| British Gas | Export Premium | 12p | British Gas electricity customers, systems up to 15kW |
| EDF | Export 12m | 13p | Existing EDF electricity customers |
| OVO | SEG Beyond Exclusive | 12p | OVO electricity customers |
| ScottishPower | SmartGen Premium | 12p | ScottishPower import customers at the same address |
| EDF / British Gas / OVO | Open SEG tariffs | 3p–4p | Anyone |
Rates from each supplier's own website, checked 23 September 2026. Some suppliers pay more (up to 17.5p–20p) only where they installed the system themselves. Rates change; check before you switch.
Payback: when do you break even?
On the assumptions above, a 4kW system without a battery pays for itself in roughly 9 to 12 years — nearer 9 in Cornwall and Bristol, nearer 12 in Manchester. Panels commonly carry 25-year performance warranties, so most systems keep generating well beyond payback, but plan for an inverter replacement at some point in the system's life and a slow decline in panel output.
Three things shorten payback more than anything: a keener price per kW, using more of the output yourself (working from home, an EV charged in the day, a heat pump, or a battery), and a better export rate. Three things lengthen it: shading, a north-facing roof, and an expensive scaffold.
Is a battery worth it?
A battery stores daytime surplus for the evening, so fewer units are exported at 12p and more replace units bought at around 26p. On the table above that lifts the value of a 4kW system by roughly £150–£190 a year. Whether that pays back depends entirely on the battery's price, which varies widely — ask for it as a separate line on the quote and divide its cost by that extra value. A battery also lets you charge from the grid on a cheap overnight tariff, which can matter more than solar storage in winter. Standalone and retrofitted batteries are also 0% VAT until March 2027. More in the battery storage guide.
Can you still get solar funded?
Rarely. ECO4 closes on 31 December 2026, and in England the Warm Homes: Local Grant can fund solar for lower-income households in homes rated EPC D to G, through councils. If that might be you, start with the solar panel grants guide. Everyone else pays, finances or subscribes — which is what the rest of this guide is about.
Does your roof work for solar?
Direction
- South-facing: the best output.
- East or west-facing: still viable — on PVGIS data an east or west roof produces about 77–80% of a south-facing one across the cities we cover.
- North-facing: usually not worth it.
Pitch
- Around 30–40 degrees is ideal; most pitched UK roofs are close enough.
- Flat roofs can work with angled frames; permitted development allows panels up to 0.6m above a flat roof.
Shade
Chimneys, trees, dormers and neighbouring buildings can cut output sharply, especially with a single string inverter. Your installer should carry out a shading assessment as part of the MCS performance estimate; on partly shaded roofs, optimisers or microinverters recover some of the loss.
When solar isn't worth it
- You expect to move within a few years and don't think the panels will add to the sale price.
- The only usable roof faces north or is heavily shaded.
- The roof needs replacing soon — do that first, or combine the jobs.
- The quote is well above the DESNZ range with no clear reason.