Solar Calculator UK 2026
Size a UK rooftop system and see your real savings under the Smart Export Guarantee (SEG). There's no upfront subsidy now — the money comes from avoiding the high import price and earning a (smaller) SEG rate on exports.
1 Your system
A typical UK home installs 3.5–5 kWp (≈ 8–12 panels).
UK averages ~900–1,000 kWh per kWp per year (south-facing); less for east/west or northern Scotland.
2 Tariffs
SEG rates as of May 2026 — they change, and you can switch export supplier independently of your import supplier. "Tied" rates require you to buy your electricity from the same supplier too.
3 Time-of-use / EV tariff
UK dynamic tariffs charge a cheap overnight rate (e.g. ~7p, 23:30–05:30) and a higher day rate. With a battery you can store cheap night grid power and day solar, then use it during expensive peak hours.
4 Battery & cost
A battery lifts self-consumption from ~35% to ~70%. Since you save the full import price (~24.5p) on self-used power but only earn the SEG rate on exports, self-consumption is worth far more.
A typical 4 kWp UK install runs ~£5,000–£8,000. Residential solar & battery carry 0% VAT in Great Britain until 31 March 2027, then revert to 5%. Note: panel prices have faced upward pressure in 2026 (changes to Chinese export-VAT rebates affecting global module costs), so quotes may run higher than older figures — enter your actual quoted price.
Indicative estimates only. SEG rates are set by suppliers and track wholesale prices; import prices change with the cap. There's no upfront government subsidy — the FiT closed to new applicants in 2019. Confirm current rates and get MCS-certified quotes before purchasing.
How this is calculated
• Self-consumption: every unit you use yourself avoids the import price (~24.5p/kWh) — the biggest saving.
• SEG export: surplus sent to the grid earns your supplier's SEG rate. These vary a lot (≈4p standard up to ~16.5p; Octopus Flux/Agile reach 24–30p at peak with a battery), and you can switch export supplier independently of your import supplier — "tied" rates require taking import from the same supplier.
Because import price is much higher than most SEG rates, using your own solar is worth roughly 2–5× more than exporting it — which is why a battery (lifting self-use ~35%→70%) helps.
Time-of-use / EV tariffs: dynamic tariffs (e.g. Octopus Intelligent Go ~7p overnight) let a battery store cheap night grid power as well as day solar. Night-charging saving = energy shifted × (day rate − night rate). Needs a battery and a TOU tariff.
Fixed vs Agile export (battery owners): with Octopus Flux paused to new signups (March 2026), battery owners compare the flat Outgoing rate (12p) against Outgoing Agile, which tracks wholesale prices — it averaged ~9.4p over the last year but spikes to 25–30p in the 4–7 PM peak, when an automated battery can sell stored solar. The comparison shows peak kWh × peak rate + remaining export × Agile average, versus all export at the fixed rate. Agile wins only if you reliably dump into the peak; otherwise fixed can be safer. These are estimates, not a half-hourly simulation.
0% VAT: residential solar & battery carry 0% VAT in Great Britain until 31 March 2027, then revert to 5% (HMRC). Enter your cost VAT-free if installing before then. You also need an MCS-certified install and a smart meter to claim SEG. SEG rates shown are as of May 2026 — verify current rates before purchasing.
Solar in the UK: how the Smart Export Guarantee works
Solar makes good sense in the UK despite its cloudy reputation — modern panels generate usefully even in diffuse light, and high electricity prices mean the power you offset is valuable. There's no upfront subsidy any more (the Feed-in Tariff closed to new applicants in 2019), but you earn from exported surplus through the Smart Export Guarantee (SEG), and you save most by using your own solar. This calculator estimates both, using SEG rates re-verified for 2026 and treating self-consumption and export separately, as honest UK solar maths requires.
SEG rates change and are presented here as dated references; confirm current tariffs before purchasing.
What the SEG is — and isn't
The Smart Export Guarantee requires larger energy suppliers to pay you for electricity you export to the grid. It replaced the more generous Feed-in Tariff, and crucially it only pays for exported units — there's no payment for what you generate and use yourself. Rates vary widely by supplier: the regulatory minimum sits around 4p/kWh, while the best flat rates are higher — for example, Octopus's popular Outgoing Fixed tariff (cut from 15p to 12p in March 2026), Good Energy around 15p, and bundled tariffs from E.ON Next and British Gas around 15–16.5p for their own import customers. Battery owners on time-of-use export tariffs (Octopus Flux and Agile) can earn 25–32p during peak windows. You'll need an MCS-certified installation and a smart meter to claim SEG.
Self-consumption beats export — by a lot
Here's the key to UK solar economics: a unit of solar you use yourself is worth far more than one you export. Using your own generation avoids buying grid electricity at the import rate (around 25p/kWh), whereas exporting earns you the SEG rate (often 4–15p). So self-consumed solar is worth roughly two to five times exported solar. That's why the falling export rates — Octopus's cut from 15p to 12p reflects a wider trend as UK solar capacity grows — matter less than people fear: the bulk of your savings comes from using your own power, not selling it. Shifting flexible loads (washing, dishwasher, hot water, EV charging) into daylight hours, or adding a battery, raises self-consumption and is the single most effective way to improve returns.
The 0% VAT window and other rules
Residential solar and battery installations currently carry 0% VAT in Great Britain until 31 March 2027, after which the rate is scheduled to return to 5% (not the standard 20%). That's a genuine, dated saving worth factoring into timing — though it's a reason to plan sensibly, not to rush into a poor decision. You'll also need an MCS-certified installer to qualify for SEG and for the VAT relief, and a smart meter to measure exports. These are practical requirements rather than obstacles, but worth knowing before you commit.
Frequently asked questions
For most homes, yes. High electricity prices mean the power you offset is valuable, and panels generate usefully even in the UK's diffuse light. The savings come mainly from self-consumption rather than export, so using your own solar (or storing it) is what makes the case strong.
Among flat rates, Octopus Outgoing Fixed (12p, reduced from 15p in March 2026), Good Energy (~15p) and bundled tariffs from E.ON Next and British Gas (~15–16.5p for their import customers) are competitive. Battery owners on time-of-use tariffs can earn 25–32p in peak windows. The standard SEG minimum is around 4p.
A battery raises self-consumption — letting you use more of your own solar instead of exporting it cheaply — and enables high-rate time-of-use export tariffs. With export rates falling, storing and using your own power is increasingly where the value lies, though a battery's cost still has to be weighed against the savings it adds.
No — the FiT closed to new applicants in 2019. New solar homes earn through the Smart Export Guarantee instead, which pays only for exported electricity. There's no upfront generation subsidy now, so the case rests on bill savings plus SEG export income.