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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in PL25 (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
11.8 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£860
What you save every year
Profit Over 25 Years
£11,336
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 1029 kWh/kW — 15 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 1029 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)
1029 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: £860, Upfront: £10,173, 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 2057 kWh 823 kWh 1234 kWh £221 £123 £344 £4,069 11.8 yrs £2,814
3 kW 3086 kWh 1234 kWh 1852 kWh £331 £185 £516 £6,104 11.8 yrs £4,221
4 kW 4115 kWh 1646 kWh 2469 kWh £441 £247 £688 £8,138 11.8 yrs £5,628
5 kW 5143 kWh 2057 kWh 3086 kWh £552 £309 £860 £10,173 11.8 yrs £7,035
6 kW 6172 kWh 2469 kWh 3703 kWh £662 £370 £1,032 £12,207 11.8 yrs £8,441
7 kW 7200 kWh 2880 kWh 4320 kWh £772 £432 £1,204 £14,242 11.8 yrs £9,848
8 kW 8229 kWh 3292 kWh 4937 kWh £883 £494 £1,377 £16,276 11.8 yrs £11,255

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: £1,033, Upfront: £12,273, Break-even: 11.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2057 kWh 1234 kWh 823 kWh £331 £82 £413 £6,169 14.9 yrs £2,098
3 kW 3086 kWh 1852 kWh 1234 kWh £497 £123 £620 £8,204 13.2 yrs £4,197
4 kW 4115 kWh 2469 kWh 1646 kWh £662 £165 £827 £10,238 12.4 yrs £6,296
5 kW 5143 kWh 3086 kWh 2057 kWh £828 £206 £1,033 £12,273 11.9 yrs £8,395
6 kW 6172 kWh 3703 kWh 2469 kWh £993 £247 £1,240 £14,307 11.5 yrs £10,494
7 kW 7200 kWh 4320 kWh 2880 kWh £1,159 £288 £1,447 £16,342 11.3 yrs £12,593
8 kW 8229 kWh 4937 kWh 3292 kWh £1,324 £329 £1,653 £18,376 11.1 yrs £14,692

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: £1,120, Upfront: £13,673, Break-even: 12.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2057 kWh 1440 kWh 617 kWh £386 £62 £448 £7,569 16.9 yrs £1,390
3 kW 3086 kWh 2160 kWh 926 kWh £579 £93 £672 £9,604 14.3 yrs £3,835
4 kW 4115 kWh 2880 kWh 1234 kWh £772 £123 £896 £11,638 13.0 yrs £6,280
5 kW 5143 kWh 3600 kWh 1543 kWh £966 £154 £1,120 £13,673 12.2 yrs £8,725
6 kW 6172 kWh 4320 kWh 1852 kWh £1,159 £185 £1,344 £15,707 11.7 yrs £11,170
7 kW 7200 kWh 5040 kWh 2160 kWh £1,352 £216 £1,568 £17,742 11.3 yrs £13,615
8 kW 8229 kWh 5760 kWh 2469 kWh £1,545 £247 £1,792 £19,776 11.0 yrs £16,060

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: £1,146, Upfront: £15,423, Break-even: 13.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2057 kWh 1502 kWh 555 kWh £403 £56 £458 £9,319 20.3 yrs £-152
3 kW 3086 kWh 2253 kWh 833 kWh £604 £83 £687 £11,354 16.5 yrs £2,396
4 kW 4115 kWh 3004 kWh 1111 kWh £806 £111 £917 £13,388 14.6 yrs £4,945
5 kW 5143 kWh 3755 kWh 1389 kWh £1,007 £139 £1,146 £15,423 13.5 yrs £7,494
6 kW 6172 kWh 4505 kWh 1666 kWh £1,208 £167 £1,375 £17,457 12.7 yrs £10,043
7 kW 7200 kWh 5256 kWh 1944 kWh £1,410 £194 £1,604 £19,492 12.2 yrs £12,592
8 kW 8229 kWh 6007 kWh 2222 kWh £1,611 £222 £1,833 £21,526 11.7 yrs £15,141

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: £1,163, Upfront: £17,173, Break-even: 14.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2057 kWh 1543 kWh 514 kWh £414 £51 £465 £11,069 23.8 yrs £-1,764
3 kW 3086 kWh 2314 kWh 771 kWh £621 £77 £698 £13,104 18.8 yrs £854
4 kW 4115 kWh 3086 kWh 1029 kWh £828 £103 £931 £15,138 16.3 yrs £3,472
5 kW 5143 kWh 3857 kWh 1286 kWh £1,035 £129 £1,163 £17,173 14.8 yrs £6,090
6 kW 6172 kWh 4629 kWh 1543 kWh £1,241 £154 £1,396 £19,207 13.8 yrs £8,708
7 kW 7200 kWh 5400 kWh 1800 kWh £1,448 £180 £1,628 £21,242 13.0 yrs £11,326
8 kW 8229 kWh 6172 kWh 2057 kWh £1,655 £206 £1,861 £23,276 12.5 yrs £13,944

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: £1,180, Upfront: £19,623, Break-even: 16.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2057 kWh 1584 kWh 473 kWh £425 £47 £472 £13,519 28.6 yrs £-4,076
3 kW 3086 kWh 2376 kWh 710 kWh £637 £71 £708 £15,554 22.0 yrs £-1,388
4 kW 4115 kWh 3168 kWh 946 kWh £850 £95 £944 £17,588 18.6 yrs £1,299
5 kW 5143 kWh 3960 kWh 1183 kWh £1,062 £118 £1,180 £19,623 16.6 yrs £3,986
6 kW 6172 kWh 4752 kWh 1420 kWh £1,275 £142 £1,417 £21,657 15.3 yrs £6,673
7 kW 7200 kWh 5544 kWh 1656 kWh £1,487 £166 £1,653 £23,692 14.3 yrs £9,361
8 kW 8229 kWh 6336 kWh 1893 kWh £1,699 £189 £1,889 £25,726 13.6 yrs £12,048

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 PL25

Figures below are tailored to PL25 — click through for full league tables.

Big-Roof Britain Rank #1193 of 2182
4.9 kWp (UK avg 5.1 kWp)
~10 panels (≈430 W)
Solar Payback Index Rank #339 of 2997
10.3 years (UK avg 11.3 years)
~£990 /yr • £10,173 upfront
Standing-Charge Drag Rank #1387 of 2997
19.9% (UK avg 21.7%) drag on savings
£197 fixed • ~£990 /yr value

Your Area at a Glance

Your Electricity Rate
26.82p/kWh
Daily Fixed Charge
54.03p/day
Local Sunshine
1029kWh/kW
A 1 kW system generates ~1029 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: 60% • Flats: 25% • Bungalows: 14% Based on 8,287 properties

Coverage

Cornwall (100%)

Areas Covered

St Austell Bethel & Holmbush, St Austell Central & Gover, St Austell Poltair & Mount Charles, Mevagissey & St Austell Bay, Penwithick & Boscoppa, St Mewan & Grampound, Truro Moresk & Trehaverne, St Blazey + 1 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

PL26 (Cornwall)
≈3.7 km away
Local sunshine: ~1,028 kWh/kWp · -0% vs PL25
PL24 (Cornwall)
≈4.6 km away
Local sunshine: ~1,049 kWh/kWp · +2% vs PL25
PL23 (Cornwall)
≈9.8 km away
Local sunshine: ~1,041 kWh/kWp · +1% vs PL25
PL22 (Cornwall)
≈10.7 km away
Local sunshine: ~1,019 kWh/kWp · -1% vs PL25
TR9 (Cornwall)
≈14.2 km away
Local sunshine: ~988 kWh/kWp · -4% vs PL25
PL31 (Cornwall)
≈14.8 km away
Local sunshine: ~982 kWh/kWp · -5% vs PL25

Similar sunshine across the UK

IP14 (Mid Suffolk)
~1,029 kWh/kWp · -0% vs PL25
NR30 (Great Yarmouth)
~1,028 kWh/kWp · -0% vs PL25
SP2 (Wiltshire)
~1,028 kWh/kWp · -0% vs PL25