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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SN25 (Swindon)

See if solar pays off for you in Swindon — 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
12.4 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£821
What you save every year
Profit Over 25 Years
£10,341
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, the current unit rate is 26.48p/kWh with a 44.62p/day standing charge. Your postcode’s south-facing sunshine yield is 989 kWh/kW — 12 below the regional median (1001).

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 989 kWh per year on a south-facing roof. We value self-used electricity at 26.5p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.5p/kWh
Standing charge
44.6p/day
Sunshine yield (south)
989 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: £821, Upfront: £10,173, Break-even: 12.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1978 kWh 791 kWh 1187 kWh £210 £119 £328 £4,069 12.4 yrs £2,495
3 kW 2967 kWh 1187 kWh 1780 kWh £314 £178 £492 £6,104 12.4 yrs £3,743
4 kW 3956 kWh 1583 kWh 2374 kWh £419 £237 £656 £8,138 12.4 yrs £4,990
5 kW 4945 kWh 1978 kWh 2967 kWh £524 £297 £821 £10,173 12.4 yrs £6,238
6 kW 5934 kWh 2374 kWh 3561 kWh £629 £356 £985 £12,207 12.4 yrs £7,486
7 kW 6923 kWh 2769 kWh 4154 kWh £733 £415 £1,149 £14,242 12.4 yrs £8,733
8 kW 7913 kWh 3165 kWh 4748 kWh £838 £475 £1,313 £16,276 12.4 yrs £9,981

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: £984, Upfront: £12,273, Break-even: 12.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1978 kWh 1187 kWh 791 kWh £314 £79 £393 £6,169 15.7 yrs £1,699
3 kW 2967 kWh 1780 kWh 1187 kWh £471 £119 £590 £8,204 13.9 yrs £3,599
4 kW 3956 kWh 2374 kWh 1583 kWh £629 £158 £787 £10,238 13.0 yrs £5,498
5 kW 4945 kWh 2967 kWh 1978 kWh £786 £198 £984 £12,273 12.5 yrs £7,398
6 kW 5934 kWh 3561 kWh 2374 kWh £943 £237 £1,180 £14,307 12.1 yrs £9,298
7 kW 6923 kWh 4154 kWh 2769 kWh £1,100 £277 £1,377 £16,342 11.9 yrs £11,197
8 kW 7913 kWh 4748 kWh 3165 kWh £1,257 £317 £1,574 £18,376 11.7 yrs £13,097

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: £1,065, Upfront: £13,673, Break-even: 12.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1978 kWh 1385 kWh 593 kWh £367 £59 £426 £7,569 17.8 yrs £951
3 kW 2967 kWh 2077 kWh 890 kWh £550 £89 £639 £9,604 15.0 yrs £3,177
4 kW 3956 kWh 2769 kWh 1187 kWh £733 £119 £852 £11,638 13.7 yrs £5,402
5 kW 4945 kWh 3462 kWh 1484 kWh £917 £148 £1,065 £13,673 12.8 yrs £7,628
6 kW 5934 kWh 4154 kWh 1780 kWh £1,100 £178 £1,278 £15,707 12.3 yrs £9,854
7 kW 6923 kWh 4846 kWh 2077 kWh £1,283 £208 £1,491 £17,742 11.9 yrs £12,079
8 kW 7913 kWh 5539 kWh 2374 kWh £1,467 £237 £1,704 £19,776 11.6 yrs £14,305

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: £1,089, Upfront: £15,423, 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 1978 kWh 1444 kWh 534 kWh £382 £53 £436 £9,319 21.4 yrs £-603
3 kW 2967 kWh 2166 kWh 801 kWh £574 £80 £654 £11,354 17.4 yrs £1,720
4 kW 3956 kWh 2888 kWh 1068 kWh £765 £107 £872 £13,388 15.4 yrs £4,044
5 kW 4945 kWh 3610 kWh 1335 kWh £956 £134 £1,089 £15,423 14.2 yrs £6,367
6 kW 5934 kWh 4332 kWh 1602 kWh £1,147 £160 £1,307 £17,457 13.4 yrs £8,690
7 kW 6923 kWh 5054 kWh 1869 kWh £1,338 £187 £1,525 £19,492 12.8 yrs £11,014
8 kW 7913 kWh 5776 kWh 2136 kWh £1,530 £214 £1,743 £21,526 12.3 yrs £13,337

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: £1,106, Upfront: £17,173, Break-even: 15.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1978 kWh 1484 kWh 495 kWh £393 £49 £442 £11,069 25.0 yrs £-2,223
3 kW 2967 kWh 2225 kWh 742 kWh £589 £74 £663 £13,104 19.8 yrs £166
4 kW 3956 kWh 2967 kWh 989 kWh £786 £99 £885 £15,138 17.1 yrs £2,554
5 kW 4945 kWh 3709 kWh 1236 kWh £982 £124 £1,106 £17,173 15.5 yrs £4,943
6 kW 5934 kWh 4451 kWh 1484 kWh £1,179 £148 £1,327 £19,207 14.5 yrs £7,332
7 kW 6923 kWh 5193 kWh 1731 kWh £1,375 £173 £1,548 £21,242 13.7 yrs £9,720
8 kW 7913 kWh 5934 kWh 1978 kWh £1,571 £198 £1,769 £23,276 13.2 yrs £12,109

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: £1,122, Upfront: £19,623, Break-even: 17.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1978 kWh 1523 kWh 455 kWh £403 £45 £449 £13,519 30.1 yrs £-4,542
3 kW 2967 kWh 2285 kWh 682 kWh £605 £68 £673 £15,554 23.1 yrs £-2,089
4 kW 3956 kWh 3046 kWh 910 kWh £807 £91 £898 £17,588 19.6 yrs £365
5 kW 4945 kWh 3808 kWh 1137 kWh £1,008 £114 £1,122 £19,623 17.5 yrs £2,819
6 kW 5934 kWh 4570 kWh 1365 kWh £1,210 £136 £1,346 £21,657 16.1 yrs £5,273
7 kW 6923 kWh 5331 kWh 1592 kWh £1,412 £159 £1,571 £23,692 15.1 yrs £7,727
8 kW 7913 kWh 6093 kWh 1820 kWh £1,613 £182 £1,795 £25,726 14.3 yrs £10,180

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 SN25

Figures below are tailored to SN25 — click through for full league tables.

Big-Roof Britain Rank #1088 of 2182
5.0 kWp (UK avg 5.1 kWp)
~10 panels (≈430 W)
Solar Payback Index Rank #1074 of 2997
10.8 years (UK avg 11.3 years)
~£943 /yr • £10,173 upfront
Standing-Charge Drag Rank #825 of 2997
17.3% (UK avg 21.7%) drag on savings
£163 fixed • ~£943 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
989kWh/kW
A 1 kW system generates ~989 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: 72% • Flats: 21% • Bungalows: 4% Based on 11,255 properties

Coverage

Swindon (100%)

Areas Covered

St Andrews, Priory Vale, Haydon Wick, Rodbourne Cheney, Covingham and Dorcan, Gorse Hill and Pinehurst, Penhill and Upper Stratton, Blunsdon and Highworth + 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

SN26 (Swindon)
≈2.3 km away
Local sunshine: ~991 kWh/kWp · +0% vs SN25
SN2 (Swindon)
≈2.6 km away
Local sunshine: ~990 kWh/kWp · +0% vs SN25
SN38 (Swindon)
≈4.0 km away
Local sunshine: ~990 kWh/kWp · +0% vs SN25
SN5 (Swindon)
≈4.3 km away
Local sunshine: ~989 kWh/kWp · -0% vs SN25
SN1 (Swindon)
≈4.9 km away
Local sunshine: ~990 kWh/kWp · +0% vs SN25
SN17 (Swindon)
≈6.3 km away
Local sunshine: ~993 kWh/kWp · +0% vs SN25

Similar sunshine across the UK

W8 (Kensington and Chelsea)
~989 kWh/kWp · -0% vs SN25
KT22 (Mole Valley)
~989 kWh/kWp · +0% vs SN25
SW3 (Kensington and Chelsea)
~989 kWh/kWp · -0% vs SN25