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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TR27 (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
£10,173
What you pay to get started
Annual Benefit
£893
What you save every year
Profit Over 25 Years
£12,148
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 5.0 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: £893, 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 2135 kWh 854 kWh 1281 kWh £229 £128 £357 £4,069 11.4 yrs £3,074
3 kW 3202 kWh 1281 kWh 1921 kWh £344 £192 £536 £6,104 11.4 yrs £4,610
4 kW 4270 kWh 1708 kWh 2562 kWh £458 £256 £714 £8,138 11.4 yrs £6,147
5 kW 5337 kWh 2135 kWh 3202 kWh £573 £320 £893 £10,173 11.4 yrs £7,684
6 kW 6405 kWh 2562 kWh 3843 kWh £687 £384 £1,071 £12,207 11.4 yrs £9,221
7 kW 7472 kWh 2989 kWh 4483 kWh £802 £448 £1,250 £14,242 11.4 yrs £10,757
8 kW 8540 kWh 3416 kWh 5124 kWh £916 £512 £1,429 £16,276 11.4 yrs £12,294

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 2135 kWh 1281 kWh 854 kWh £344 £85 £429 £6,169 14.4 yrs £2,410
3 kW 3202 kWh 1921 kWh 1281 kWh £515 £128 £643 £8,204 12.7 yrs £4,665
4 kW 4270 kWh 2562 kWh 1708 kWh £687 £171 £858 £10,238 11.9 yrs £6,920
5 kW 5337 kWh 3202 kWh 2135 kWh £859 £213 £1,072 £12,273 11.4 yrs £9,175
6 kW 6405 kWh 3843 kWh 2562 kWh £1,031 £256 £1,287 £14,307 11.1 yrs £11,430
7 kW 7472 kWh 4483 kWh 2989 kWh £1,202 £299 £1,501 £16,342 10.9 yrs £13,685
8 kW 8540 kWh 5124 kWh 3416 kWh £1,374 £342 £1,716 £18,376 10.7 yrs £15,939

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 2135 kWh 1494 kWh 640 kWh £401 £64 £465 £7,569 16.3 yrs £1,728
3 kW 3202 kWh 2242 kWh 961 kWh £601 £96 £697 £9,604 13.8 yrs £4,342
4 kW 4270 kWh 2989 kWh 1281 kWh £802 £128 £930 £11,638 12.5 yrs £6,956
5 kW 5337 kWh 3736 kWh 1601 kWh £1,002 £160 £1,162 £13,673 11.8 yrs £9,570
6 kW 6405 kWh 4483 kWh 1921 kWh £1,202 £192 £1,395 £15,707 11.3 yrs £12,184
7 kW 7472 kWh 5231 kWh 2242 kWh £1,403 £224 £1,627 £17,742 10.9 yrs £14,798
8 kW 8540 kWh 5978 kWh 2562 kWh £1,603 £256 £1,859 £19,776 10.6 yrs £17,412

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 2135 kWh 1558 kWh 576 kWh £418 £58 £476 £9,319 19.6 yrs £193
3 kW 3202 kWh 2338 kWh 865 kWh £627 £86 £713 £11,354 15.9 yrs £2,915
4 kW 4270 kWh 3117 kWh 1153 kWh £836 £115 £951 £13,388 14.1 yrs £5,637
5 kW 5337 kWh 3896 kWh 1441 kWh £1,045 £144 £1,189 £15,423 13.0 yrs £8,359
6 kW 6405 kWh 4675 kWh 1729 kWh £1,254 £173 £1,427 £17,457 12.2 yrs £11,080
7 kW 7472 kWh 5455 kWh 2017 kWh £1,463 £202 £1,665 £19,492 11.7 yrs £13,802
8 kW 8540 kWh 6234 kWh 2306 kWh £1,672 £231 £1,903 £21,526 11.3 yrs £16,524

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: £1,207, 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 2135 kWh 1601 kWh 534 kWh £429 £53 £483 £11,069 22.9 yrs £-1,413
3 kW 3202 kWh 2402 kWh 801 kWh £644 £80 £724 £13,104 18.1 yrs £1,381
4 kW 4270 kWh 3202 kWh 1067 kWh £859 £107 £966 £15,138 15.7 yrs £4,174
5 kW 5337 kWh 4003 kWh 1334 kWh £1,074 £133 £1,207 £17,173 14.2 yrs £6,968
6 kW 6405 kWh 4804 kWh 1601 kWh £1,288 £160 £1,448 £19,207 13.3 yrs £9,761
7 kW 7472 kWh 5604 kWh 1868 kWh £1,503 £187 £1,690 £21,242 12.6 yrs £12,555
8 kW 8540 kWh 6405 kWh 2135 kWh £1,718 £213 £1,931 £23,276 12.1 yrs £15,349

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: £1,225, 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 2135 kWh 1644 kWh 491 kWh £441 £49 £490 £13,519 27.6 yrs £-3,719
3 kW 3202 kWh 2466 kWh 737 kWh £661 £74 £735 £15,554 21.2 yrs £-854
4 kW 4270 kWh 3288 kWh 982 kWh £882 £98 £980 £17,588 17.9 yrs £2,012
5 kW 5337 kWh 4110 kWh 1228 kWh £1,102 £123 £1,225 £19,623 16.0 yrs £4,877
6 kW 6405 kWh 4932 kWh 1473 kWh £1,323 £147 £1,470 £21,657 14.7 yrs £7,742
7 kW 7472 kWh 5754 kWh 1719 kWh £1,543 £172 £1,715 £23,692 13.8 yrs £10,608
8 kW 8540 kWh 6575 kWh 1964 kWh £1,764 £196 £1,960 £25,726 13.1 yrs £13,473

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 TR27

Figures below are tailored to TR27 — click through for full league tables.

Big-Roof Britain Rank #832 of 2182
5.2 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #173 of 2997
9.9 years (UK avg 11.3 years)
~£1,027 /yr • £10,173 upfront
Standing-Charge Drag Rank #1252 of 2997
19.2% (UK avg 21.7%) drag on savings
£197 fixed • ~£1,027 /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
5.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 64% • Flats: 12% • Bungalows: 24% Based on 5,360 properties

Coverage

Cornwall (100%)

Areas Covered

Hayle West, Gwinear-Gwithian & Hayle East, Long Rock, Marazion & St Erth, St Ives East, Lelant & Carbis Bay, Crowan, Sithney & Wendron + 3 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

TR26 (Cornwall)
≈5.4 km away
Local sunshine: ~1,009 kWh/kWp · -5% vs TR27
TR17 (Cornwall)
≈7.7 km away
Local sunshine: ~1,067 kWh/kWp · -0% vs TR27
TR20 (Cornwall)
≈8.5 km away
Local sunshine: ~1,067 kWh/kWp · -0% vs TR27
TR14 (Cornwall)
≈8.9 km away
Local sunshine: ~1,008 kWh/kWp · -6% vs TR27
TR93 (Cornwall)
≈8.9 km away
Local sunshine: ~1,066 kWh/kWp · -0% vs TR27
TR18 (Cornwall)
≈11.6 km away
Local sunshine: ~1,066 kWh/kWp · -0% vs TR27

Similar sunshine across the UK

SO42 (New Forest)
~1,068 kWh/kWp · +0% vs TR27
IP10 (East Suffolk)
~1,068 kWh/kWp · +0% vs TR27
PO31 (Isle of Wight)
~1,067 kWh/kWp · -0% vs TR27