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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TR20 (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
11.4 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£1,071
What you save every year
Profit Over 25 Years
£14,565
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

In Southern Western, the current unit rate is 26.82p/kWh with a 54.03p/day standing charge. Your postcode’s south-facing sunshine yield is 1067 kWh/kW — 54 above the regional median (1013).

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 1067 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)
1067 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: £892, Upfront: £10,173, Break-even: 11.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2134 kWh 854 kWh 1280 kWh £229 £128 £357 £4,069 11.4 yrs £3,070
3 kW 3201 kWh 1280 kWh 1921 kWh £343 £192 £535 £6,104 11.4 yrs £4,605
4 kW 4268 kWh 1707 kWh 2561 kWh £458 £256 £714 £8,138 11.4 yrs £6,141
5 kW 5335 kWh 2134 kWh 3201 kWh £572 £320 £892 £10,173 11.4 yrs £7,676
6 kW 6402 kWh 2561 kWh 3841 kWh £687 £384 £1,071 £12,207 11.4 yrs £9,211
7 kW 7469 kWh 2988 kWh 4481 kWh £801 £448 £1,249 £14,242 11.4 yrs £10,746
8 kW 8536 kWh 3414 kWh 5121 kWh £916 £512 £1,428 £16,276 11.4 yrs £12,281

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: £1,072, Upfront: £12,273, Break-even: 11.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2134 kWh 1280 kWh 854 kWh £343 £85 £429 £6,169 14.4 yrs £2,406
3 kW 3201 kWh 1921 kWh 1280 kWh £515 £128 £643 £8,204 12.8 yrs £4,659
4 kW 4268 kWh 2561 kWh 1707 kWh £687 £171 £858 £10,238 11.9 yrs £6,912
5 kW 5335 kWh 3201 kWh 2134 kWh £858 £213 £1,072 £12,273 11.4 yrs £9,165
6 kW 6402 kWh 3841 kWh 2561 kWh £1,030 £256 £1,286 £14,307 11.1 yrs £11,418
7 kW 7469 kWh 4481 kWh 2988 kWh £1,202 £299 £1,501 £16,342 10.9 yrs £13,671
8 kW 8536 kWh 5121 kWh 3414 kWh £1,374 £341 £1,715 £18,376 10.7 yrs £15,924

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: £1,162, Upfront: £13,673, Break-even: 11.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2134 kWh 1494 kWh 640 kWh £401 £64 £465 £7,569 16.3 yrs £1,724
3 kW 3201 kWh 2241 kWh 960 kWh £601 £96 £697 £9,604 13.8 yrs £4,336
4 kW 4268 kWh 2988 kWh 1280 kWh £801 £128 £929 £11,638 12.5 yrs £6,948
5 kW 5335 kWh 3734 kWh 1600 kWh £1,002 £160 £1,162 £13,673 11.8 yrs £9,560
6 kW 6402 kWh 4481 kWh 1921 kWh £1,202 £192 £1,394 £15,707 11.3 yrs £12,172
7 kW 7469 kWh 5228 kWh 2241 kWh £1,402 £224 £1,626 £17,742 10.9 yrs £14,784
8 kW 8536 kWh 5975 kWh 2561 kWh £1,603 £256 £1,859 £19,776 10.6 yrs £17,395

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: £1,189, Upfront: £15,423, Break-even: 13.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2134 kWh 1558 kWh 576 kWh £418 £58 £475 £9,319 19.6 yrs £189
3 kW 3201 kWh 2337 kWh 864 kWh £627 £86 £713 £11,354 15.9 yrs £2,909
4 kW 4268 kWh 3116 kWh 1152 kWh £836 £115 £951 £13,388 14.1 yrs £5,628
5 kW 5335 kWh 3894 kWh 1440 kWh £1,044 £144 £1,189 £15,423 13.0 yrs £8,348
6 kW 6402 kWh 4673 kWh 1728 kWh £1,253 £173 £1,426 £17,457 12.2 yrs £11,068
7 kW 7469 kWh 5452 kWh 2017 kWh £1,462 £202 £1,664 £19,492 11.7 yrs £13,787
8 kW 8536 kWh 6231 kWh 2305 kWh £1,671 £230 £1,902 £21,526 11.3 yrs £16,507

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: £1,206, Upfront: £17,173, Break-even: 14.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2134 kWh 1600 kWh 533 kWh £429 £53 £483 £11,069 22.9 yrs £-1,417
3 kW 3201 kWh 2401 kWh 800 kWh £644 £80 £724 £13,104 18.1 yrs £1,374
4 kW 4268 kWh 3201 kWh 1067 kWh £858 £107 £965 £15,138 15.7 yrs £4,166
5 kW 5335 kWh 4001 kWh 1334 kWh £1,073 £133 £1,206 £17,173 14.2 yrs £6,957
6 kW 6402 kWh 4801 kWh 1600 kWh £1,288 £160 £1,448 £19,207 13.3 yrs £9,748
7 kW 7469 kWh 5602 kWh 1867 kWh £1,502 £187 £1,689 £21,242 12.6 yrs £12,540
8 kW 8536 kWh 6402 kWh 2134 kWh £1,717 £213 £1,930 £23,276 12.1 yrs £15,331

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: £1,224, Upfront: £19,623, Break-even: 16.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2134 kWh 1643 kWh 491 kWh £441 £49 £490 £13,519 27.6 yrs £-3,724
3 kW 3201 kWh 2465 kWh 736 kWh £661 £74 £735 £15,554 21.2 yrs £-860
4 kW 4268 kWh 3286 kWh 982 kWh £881 £98 £980 £17,588 18.0 yrs £2,003
5 kW 5335 kWh 4108 kWh 1227 kWh £1,102 £123 £1,224 £19,623 16.0 yrs £4,866
6 kW 6402 kWh 4929 kWh 1472 kWh £1,322 £147 £1,469 £21,657 14.7 yrs £7,729
7 kW 7469 kWh 5751 kWh 1718 kWh £1,542 £172 £1,714 £23,692 13.8 yrs £10,592
8 kW 8536 kWh 6573 kWh 1963 kWh £1,763 £196 £1,959 £25,726 13.1 yrs £13,455

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.

Insights for TR20

Figures below are tailored to TR20 — click through for full league tables.

Big-Roof Britain Rank #279 of 2182
6.0 kWp (UK avg 5.1 kWp)
~13 panels (≈430 W)
Solar Payback Index Rank #171 of 2997
9.9 years (UK avg 11.3 years)
~£1,232 /yr • £12,207 upfront
Standing-Charge Drag Rank #565 of 2997
16.0% (UK avg 21.7%) drag on savings
£197 fixed • ~£1,232 /yr value

Your Area at a Glance

Your Electricity Rate
26.82p/kWh
Daily Fixed Charge
54.03p/day
Local Sunshine
1067kWh/kW
A 1 kW system generates ~1067 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: 69% • Flats: 4% • Bungalows: 26% Based on 3,250 properties

Coverage

Cornwall (100%)

Areas Covered

Long Rock, Marazion & St Erth, Ludgvan, Madron, Gulval & Heamoor, Porthleven, Breage & Germoe, Land's End + 7 more

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.

Compare nearby areas

Nearby in Southern Western

TR93 (Cornwall)
≈0.6 km away
Local sunshine: ~1,066 kWh/kWp · -0% vs TR20
TR17 (Cornwall)
≈1.9 km away
Local sunshine: ~1,067 kWh/kWp · -0% vs TR20
TR18 (Cornwall)
≈3.4 km away
Local sunshine: ~1,066 kWh/kWp · -0% vs TR20
TR26 (Cornwall)
≈8.5 km away
Local sunshine: ~1,009 kWh/kWp · -5% vs TR20
TR27 (Cornwall)
≈8.5 km away
Local sunshine: ~1,067 kWh/kWp · +0% vs TR20
TR19 (Cornwall)
≈12.2 km away
Local sunshine: ~1,083 kWh/kWp · +2% vs TR20

Similar sunshine across the UK

PO31 (Isle of Wight)
~1,067 kWh/kWp · +0% vs TR20
BN8 (Lewes)
~1,067 kWh/kWp · -0% vs TR20
SO42 (New Forest)
~1,068 kWh/kWp · +0% vs TR20