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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TR12 (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
11.1 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£1,101
What you save every year
Profit Over 25 Years
£15,323
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 1097 kWh/kW — 84 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 1097 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)
1097 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: £918, Upfront: £10,173, Break-even: 11.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2194 kWh 878 kWh 1317 kWh £235 £132 £367 £4,069 11.1 yrs £3,272
3 kW 3291 kWh 1317 kWh 1975 kWh £353 £197 £551 £6,104 11.1 yrs £4,908
4 kW 4389 kWh 1755 kWh 2633 kWh £471 £263 £734 £8,138 11.1 yrs £6,544
5 kW 5486 kWh 2194 kWh 3291 kWh £589 £329 £918 £10,173 11.1 yrs £8,181
6 kW 6583 kWh 2633 kWh 3950 kWh £706 £395 £1,101 £12,207 11.1 yrs £9,817
7 kW 7680 kWh 3072 kWh 4608 kWh £824 £461 £1,285 £14,242 11.1 yrs £11,453
8 kW 8777 kWh 3511 kWh 5266 kWh £942 £527 £1,468 £16,276 11.1 yrs £13,089

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: £1,102, Upfront: £12,273, Break-even: 11.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2194 kWh 1317 kWh 878 kWh £353 £88 £441 £6,169 14.0 yrs £2,649
3 kW 3291 kWh 1975 kWh 1317 kWh £530 £132 £661 £8,204 12.4 yrs £5,023
4 kW 4389 kWh 2633 kWh 1755 kWh £706 £176 £882 £10,238 11.6 yrs £7,397
5 kW 5486 kWh 3291 kWh 2194 kWh £883 £219 £1,102 £12,273 11.1 yrs £9,771
6 kW 6583 kWh 3950 kWh 2633 kWh £1,059 £263 £1,323 £14,307 10.8 yrs £12,146
7 kW 7680 kWh 4608 kWh 3072 kWh £1,236 £307 £1,543 £16,342 10.6 yrs £14,520
8 kW 8777 kWh 5266 kWh 3511 kWh £1,412 £351 £1,764 £18,376 10.4 yrs £16,894

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: £1,194, Upfront: £13,673, 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 2194 kWh 1536 kWh 658 kWh £412 £66 £478 £7,569 15.8 yrs £1,987
3 kW 3291 kWh 2304 kWh 987 kWh £618 £99 £717 £9,604 13.4 yrs £4,730
4 kW 4389 kWh 3072 kWh 1317 kWh £824 £132 £956 £11,638 12.2 yrs £7,473
5 kW 5486 kWh 3840 kWh 1646 kWh £1,030 £165 £1,194 £13,673 11.4 yrs £10,217
6 kW 6583 kWh 4608 kWh 1975 kWh £1,236 £197 £1,433 £15,707 11.0 yrs £12,960
7 kW 7680 kWh 5376 kWh 2304 kWh £1,442 £230 £1,672 £17,742 10.6 yrs £15,704
8 kW 8777 kWh 6144 kWh 2633 kWh £1,648 £263 £1,911 £19,776 10.3 yrs £18,447

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: £1,222, Upfront: £15,423, Break-even: 12.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2194 kWh 1602 kWh 592 kWh £430 £59 £489 £9,319 19.1 yrs £458
3 kW 3291 kWh 2403 kWh 889 kWh £644 £89 £733 £11,354 15.5 yrs £3,312
4 kW 4389 kWh 3204 kWh 1185 kWh £859 £118 £978 £13,388 13.7 yrs £6,166
5 kW 5486 kWh 4005 kWh 1481 kWh £1,074 £148 £1,222 £15,423 12.6 yrs £9,020
6 kW 6583 kWh 4806 kWh 1777 kWh £1,289 £178 £1,467 £17,457 11.9 yrs £11,874
7 kW 7680 kWh 5606 kWh 2074 kWh £1,504 £207 £1,711 £19,492 11.4 yrs £14,729
8 kW 8777 kWh 6407 kWh 2370 kWh £1,718 £237 £1,955 £21,526 11.0 yrs £17,583

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: £1,241, Upfront: £17,173, Break-even: 13.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2194 kWh 1646 kWh 549 kWh £441 £55 £496 £11,069 22.3 yrs £-1,144
3 kW 3291 kWh 2469 kWh 823 kWh £662 £82 £744 £13,104 17.6 yrs £1,784
4 kW 4389 kWh 3291 kWh 1097 kWh £883 £110 £992 £15,138 15.3 yrs £4,712
5 kW 5486 kWh 4114 kWh 1371 kWh £1,103 £137 £1,241 £17,173 13.8 yrs £7,639
6 kW 6583 kWh 4937 kWh 1646 kWh £1,324 £165 £1,489 £19,207 12.9 yrs £10,567
7 kW 7680 kWh 5760 kWh 1920 kWh £1,545 £192 £1,737 £21,242 12.2 yrs £13,495
8 kW 8777 kWh 6583 kWh 2194 kWh £1,766 £219 £1,985 £23,276 11.7 yrs £16,423

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: £1,259, Upfront: £19,623, Break-even: 15.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2194 kWh 1690 kWh 505 kWh £453 £50 £504 £13,519 26.8 yrs £-3,447
3 kW 3291 kWh 2534 kWh 757 kWh £680 £76 £755 £15,554 20.6 yrs £-445
4 kW 4389 kWh 3379 kWh 1009 kWh £906 £101 £1,007 £17,588 17.5 yrs £2,557
5 kW 5486 kWh 4224 kWh 1262 kWh £1,133 £126 £1,259 £19,623 15.6 yrs £5,559
6 kW 6583 kWh 5069 kWh 1514 kWh £1,359 £151 £1,511 £21,657 14.3 yrs £8,560
7 kW 7680 kWh 5914 kWh 1766 kWh £1,586 £177 £1,763 £23,692 13.4 yrs £11,562
8 kW 8777 kWh 6758 kWh 2019 kWh £1,813 £202 £2,014 £25,726 12.8 yrs £14,564

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 TR12

Figures below are tailored to TR12 — click through for full league tables.

Big-Roof Britain Rank #103 of 2182
6.5 kWp (UK avg 5.1 kWp)
~14 panels (≈430 W)
Solar Payback Index Rank #74 of 2997
9.6 years (UK avg 11.3 years)
~£1,267 /yr • £12,207 upfront
Standing-Charge Drag Rank #512 of 2997
15.6% (UK avg 21.7%) drag on savings
£197 fixed • ~£1,267 /yr value

Your Area at a Glance

Your Electricity Rate
26.82p/kWh
Daily Fixed Charge
54.03p/day
Local Sunshine
1097kWh/kW
A 1 kW system generates ~1097 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: 60% • Flats: 6% • Bungalows: 34% Based on 3,240 properties

Coverage

Cornwall (100%)

Areas Covered

Mullion & St Keverne, Helston South & Meneage, Constantine, Mabe & Mawnan

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

TR13 (Cornwall)
≈8.0 km away
Local sunshine: ~1,082 kWh/kWp · -1% vs TR12
TR11 (Cornwall)
≈14.3 km away
Local sunshine: ~1,021 kWh/kWp · -7% vs TR12
TR10 (Cornwall)
≈14.7 km away
Local sunshine: ~1,027 kWh/kWp · -6% vs TR12
TR14 (Cornwall)
≈19.5 km away
Local sunshine: ~1,008 kWh/kWp · -8% vs TR12
TR3 (Cornwall)
≈19.7 km away
Local sunshine: ~1,038 kWh/kWp · -5% vs TR12
TR15 (Cornwall)
≈20.6 km away
Local sunshine: ~1,012 kWh/kWp · -8% vs TR12

Similar sunshine across the UK

PO11 (Havant)
~1,096 kWh/kWp · -0% vs TR12
PO9 (Havant)
~1,096 kWh/kWp · -0% vs TR12
PO2 (Portsmouth)
~1,096 kWh/kWp · -0% vs TR12