Solar explained to clever people by people who are not trying to be clever

Solar Panels in PL23 (Cornwall)

See if solar pays off for you in Cornwall — price, savings and payback in under a minute (official UK data).

Solar Calculator

Change the settings below to see how costs and savings work for your situation.

System Size

Roof Direction

Battery Storage

Export Value

Your Numbers

Break-even
11.7 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£1,045
What you save every year
Profit Over 25 Years
£13,924
After paying itself off, you're this much ahead

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How we calculate this

Solar generation: Based on typical south-facing roof at 35° angle. We account for weather, dirt, and system losses (14%).

How much you'll use directly:

  • Without battery: You'll use about 40% of what you generate. The rest gets sold back to the grid.
  • With 5 kWh battery: You'll use about 70% (battery stores extra for evening use).
  • With 10 kWh battery: You'll use about 75% (more storage means less exported).
  • Panel-only payback: Bigger systems don’t shorten payback—cost and savings rise together per kW.
  • Battery & payback: Batteries raise self-use and cut bills, but added hardware cost often lengthens break-even at typical UK rates.
  • When a battery can still make sense:
    • Evening-heavy usage patterns
    • Time-of-use tariffs / cheap night rates
    • Low export rate vs. high unit rate
    • Heat pump or EV charging synergy
    • Optional backup/resilience (system-dependent)
    • Lower evening-hour CO₂ vs. grid

Costs: Battery prices are typically £700 per kWh. Export tariffs vary by supplier (usually 5–15p per kWh).

Grid connection: Systems up to about 3.7 kW typically need just a notification (G98). Larger systems may need permission (G99).

These are typical values based on average usage patterns. Your actual results will vary based on your roof, shading, and how you use electricity.

Your area in context

Read the full story

A typical roof here lands around 6.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 1041 kWh per year on a south-facing roof. We value self-used electricity at 26.8p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.8p/kWh
Standing charge
54.0p/day
Sunshine yield (south)
1041 kWh/kW
Export price (baseline)
10p/kWh

Browse the scenarios below. Each battery size has its own expand — open the one that matches your plan (or just explore). For each system size (2–8 kW) we show annual output, how much you use directly, what gets exported, annual benefit, upfront cost, break-even, and a 20-year net. Negative numbers are possible — that’s the honest trade-off when adding more battery than your usage profile justifies.

No battery 5 kW example → Annual benefit: £871, Upfront: £10,173, Break-even: 11.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 833 kWh 1250 kWh £223 £125 £348 £4,069 11.7 yrs £2,899
3 kW 3124 kWh 1250 kWh 1875 kWh £335 £187 £523 £6,104 11.7 yrs £4,349
4 kW 4166 kWh 1666 kWh 2499 kWh £447 £250 £697 £8,138 11.7 yrs £5,799
5 kW 5207 kWh 2083 kWh 3124 kWh £559 £312 £871 £10,173 11.7 yrs £7,248
6 kW 6248 kWh 2499 kWh 3749 kWh £670 £375 £1,045 £12,207 11.7 yrs £8,698
7 kW 7290 kWh 2916 kWh 4374 kWh £782 £437 £1,219 £14,242 11.7 yrs £10,147
8 kW 8331 kWh 3333 kWh 4999 kWh £894 £500 £1,394 £16,276 11.7 yrs £11,597

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

3 kWh battery 5 kW example → Annual benefit: £1,046, Upfront: £12,273, Break-even: 11.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1250 kWh 833 kWh £335 £83 £418 £6,169 14.7 yrs £2,201
3 kW 3124 kWh 1875 kWh 1250 kWh £503 £125 £628 £8,204 13.1 yrs £4,351
4 kW 4166 kWh 2499 kWh 1666 kWh £670 £167 £837 £10,238 12.2 yrs £6,501
5 kW 5207 kWh 3124 kWh 2083 kWh £838 £208 £1,046 £12,273 11.7 yrs £8,651
6 kW 6248 kWh 3749 kWh 2499 kWh £1,006 £250 £1,255 £14,307 11.4 yrs £10,802
7 kW 7290 kWh 4374 kWh 2916 kWh £1,173 £292 £1,465 £16,342 11.2 yrs £12,952
8 kW 8331 kWh 4999 kWh 3333 kWh £1,341 £333 £1,674 £18,376 11.0 yrs £15,102

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

5 kWh battery 5 kW example → Annual benefit: £1,134, Upfront: £13,673, Break-even: 12.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1458 kWh 625 kWh £391 £62 £454 £7,569 16.7 yrs £1,501
3 kW 3124 kWh 2187 kWh 937 kWh £587 £94 £680 £9,604 14.1 yrs £4,002
4 kW 4166 kWh 2916 kWh 1250 kWh £782 £125 £907 £11,638 12.8 yrs £6,502
5 kW 5207 kWh 3645 kWh 1562 kWh £978 £156 £1,134 £13,673 12.1 yrs £9,003
6 kW 6248 kWh 4374 kWh 1875 kWh £1,173 £187 £1,361 £15,707 11.5 yrs £11,504
7 kW 7290 kWh 5103 kWh 2187 kWh £1,369 £219 £1,587 £17,742 11.2 yrs £14,004
8 kW 8331 kWh 5832 kWh 2499 kWh £1,564 £250 £1,814 £19,776 10.9 yrs £16,505

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

7.5 kWh battery 5 kW example → Annual benefit: £1,160, Upfront: £15,423, Break-even: 13.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1520 kWh 562 kWh £408 £56 £464 £9,319 20.1 yrs £-39
3 kW 3124 kWh 2281 kWh 844 kWh £612 £84 £696 £11,354 16.3 yrs £2,567
4 kW 4166 kWh 3041 kWh 1125 kWh £816 £112 £928 £13,388 14.4 yrs £5,173
5 kW 5207 kWh 3801 kWh 1406 kWh £1,019 £141 £1,160 £15,423 13.3 yrs £7,779
6 kW 6248 kWh 4561 kWh 1687 kWh £1,223 £169 £1,392 £17,457 12.5 yrs £10,384
7 kW 7290 kWh 5322 kWh 1968 kWh £1,427 £197 £1,624 £19,492 12.0 yrs £12,990
8 kW 8331 kWh 6082 kWh 2249 kWh £1,631 £225 £1,856 £21,526 11.6 yrs £15,596

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

10 kWh battery 5 kW example → Annual benefit: £1,178, Upfront: £17,173, Break-even: 14.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1562 kWh 521 kWh £419 £52 £471 £11,069 23.5 yrs £-1,648
3 kW 3124 kWh 2343 kWh 781 kWh £628 £78 £707 £13,104 18.5 yrs £1,027
4 kW 4166 kWh 3124 kWh 1041 kWh £838 £104 £942 £15,138 16.1 yrs £3,703
5 kW 5207 kWh 3905 kWh 1302 kWh £1,047 £130 £1,178 £17,173 14.6 yrs £6,379
6 kW 6248 kWh 4686 kWh 1562 kWh £1,257 £156 £1,413 £19,207 13.6 yrs £9,055
7 kW 7290 kWh 5467 kWh 1822 kWh £1,466 £182 £1,649 £21,242 12.9 yrs £11,731
8 kW 8331 kWh 6248 kWh 2083 kWh £1,676 £208 £1,884 £23,276 12.4 yrs £14,406

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

13.5 kWh battery 5 kW example → Annual benefit: £1,195, Upfront: £19,623, Break-even: 16.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1604 kWh 479 kWh £430 £48 £478 £13,519 28.3 yrs £-3,958
3 kW 3124 kWh 2406 kWh 719 kWh £645 £72 £717 £15,554 21.7 yrs £-1,212
4 kW 4166 kWh 3208 kWh 958 kWh £860 £96 £956 £17,588 18.4 yrs £1,533
5 kW 5207 kWh 4009 kWh 1198 kWh £1,075 £120 £1,195 £19,623 16.4 yrs £4,279
6 kW 6248 kWh 4811 kWh 1437 kWh £1,290 £144 £1,434 £21,657 15.1 yrs £7,025
7 kW 7290 kWh 5613 kWh 1677 kWh £1,505 £168 £1,673 £23,692 14.2 yrs £9,771
8 kW 8331 kWh 6415 kWh 1916 kWh £1,721 £192 £1,912 £25,726 13.5 yrs £12,517

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 2,035, battery £/kWh = 700.

Figures are illustrative and use the same method as the calculator above. For exact results, adjust your roof direction, tariff, and usage in the calculator.

Your Area at a Glance

Your Electricity Rate
26.82p/kWh
Daily Fixed Charge
54.03p/day
Local Sunshine
1041kWh/kW
A 1 kW system generates ~1041 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
6.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 68% • Flats: 14% • Bungalows: 15% Based on 1,494 properties

Coverage

Cornwall (100%)

Areas Covered

Fowey, Tywardreath & Par, Looe West, Pelynt, Lansallos & Lanteglos

Data Sources & Assumptions

Solar yield: PVGIS (EU Joint Research Centre), January 2025 data

Electricity rates: Ofgem price cap, Q4 2025

Installation costs: MCS certified installer data, March 2025

Property data: EPC open data (Open Government Licence), aggregated

All estimates are typical values. Actual results vary based on your specific situation, roof characteristics, and usage patterns.