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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SN12 (Wiltshire)

See if solar pays off for you in Wiltshire — 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
12.3 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£824
What you save every year
Profit Over 25 Years
£10,434
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 994 kWh/kW — 8 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 994 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)
994 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: £824, Upfront: £10,173, Break-even: 12.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1987 kWh 795 kWh 1192 kWh £210 £119 £330 £4,069 12.3 yrs £2,525
3 kW 2981 kWh 1192 kWh 1788 kWh £316 £179 £495 £6,104 12.3 yrs £3,788
4 kW 3974 kWh 1590 kWh 2385 kWh £421 £238 £659 £8,138 12.3 yrs £5,050
5 kW 4968 kWh 1987 kWh 2981 kWh £526 £298 £824 £10,173 12.3 yrs £6,313
6 kW 5961 kWh 2385 kWh 3577 kWh £631 £358 £989 £12,207 12.3 yrs £7,575
7 kW 6955 kWh 2782 kWh 4173 kWh £737 £417 £1,154 £14,242 12.3 yrs £8,838
8 kW 7948 kWh 3179 kWh 4769 kWh £842 £477 £1,319 £16,276 12.3 yrs £10,100

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: £988, Upfront: £12,273, 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 1987 kWh 1192 kWh 795 kWh £316 £79 £395 £6,169 15.6 yrs £1,735
3 kW 2981 kWh 1788 kWh 1192 kWh £474 £119 £593 £8,204 13.8 yrs £3,652
4 kW 3974 kWh 2385 kWh 1590 kWh £631 £159 £790 £10,238 13.0 yrs £5,570
5 kW 4968 kWh 2981 kWh 1987 kWh £789 £199 £988 £12,273 12.4 yrs £7,487
6 kW 5961 kWh 3577 kWh 2385 kWh £947 £238 £1,186 £14,307 12.1 yrs £9,405
7 kW 6955 kWh 4173 kWh 2782 kWh £1,105 £278 £1,383 £16,342 11.8 yrs £11,322
8 kW 7948 kWh 4769 kWh 3179 kWh £1,263 £318 £1,581 £18,376 11.6 yrs £13,240

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: £1,070, 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 1987 kWh 1391 kWh 596 kWh £368 £60 £428 £7,569 17.7 yrs £990
3 kW 2981 kWh 2086 kWh 894 kWh £552 £89 £642 £9,604 15.0 yrs £3,235
4 kW 3974 kWh 2782 kWh 1192 kWh £737 £119 £856 £11,638 13.6 yrs £5,480
5 kW 4968 kWh 3477 kWh 1490 kWh £921 £149 £1,070 £13,673 12.8 yrs £7,725
6 kW 5961 kWh 4173 kWh 1788 kWh £1,105 £179 £1,284 £15,707 12.2 yrs £9,970
7 kW 6955 kWh 4868 kWh 2086 kWh £1,289 £209 £1,498 £17,742 11.8 yrs £12,215
8 kW 7948 kWh 5564 kWh 2385 kWh £1,473 £238 £1,712 £19,776 11.6 yrs £14,460

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: £1,094, Upfront: £15,423, Break-even: 14.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1987 kWh 1451 kWh 537 kWh £384 £54 £438 £9,319 21.3 yrs £-564
3 kW 2981 kWh 2176 kWh 805 kWh £576 £80 £657 £11,354 17.3 yrs £1,780
4 kW 3974 kWh 2901 kWh 1073 kWh £768 £107 £876 £13,388 15.3 yrs £4,123
5 kW 4968 kWh 3626 kWh 1341 kWh £960 £134 £1,094 £15,423 14.1 yrs £6,466
6 kW 5961 kWh 4352 kWh 1610 kWh £1,152 £161 £1,313 £17,457 13.3 yrs £8,809
7 kW 6955 kWh 5077 kWh 1878 kWh £1,344 £188 £1,532 £19,492 12.7 yrs £11,152
8 kW 7948 kWh 5802 kWh 2146 kWh £1,536 £215 £1,751 £21,526 12.3 yrs £13,496

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: £1,111, 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 1987 kWh 1490 kWh 497 kWh £395 £50 £444 £11,069 24.9 yrs £-2,183
3 kW 2981 kWh 2236 kWh 745 kWh £592 £75 £666 £13,104 19.7 yrs £226
4 kW 3974 kWh 2981 kWh 994 kWh £789 £99 £889 £15,138 17.0 yrs £2,635
5 kW 4968 kWh 3726 kWh 1242 kWh £987 £124 £1,111 £17,173 15.5 yrs £5,043
6 kW 5961 kWh 4471 kWh 1490 kWh £1,184 £149 £1,333 £19,207 14.4 yrs £7,452
7 kW 6955 kWh 5216 kWh 1739 kWh £1,381 £174 £1,555 £21,242 13.7 yrs £9,861
8 kW 7948 kWh 5961 kWh 1987 kWh £1,579 £199 £1,777 £23,276 13.1 yrs £12,270

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: £1,127, Upfront: £19,623, Break-even: 17.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1987 kWh 1530 kWh 457 kWh £405 £46 £451 £13,519 30.0 yrs £-4,502
3 kW 2981 kWh 2295 kWh 686 kWh £608 £69 £676 £15,554 23.0 yrs £-2,027
4 kW 3974 kWh 3060 kWh 914 kWh £810 £91 £902 £17,588 19.5 yrs £447
5 kW 4968 kWh 3825 kWh 1143 kWh £1,013 £114 £1,127 £19,623 17.4 yrs £2,921
6 kW 5961 kWh 4590 kWh 1371 kWh £1,215 £137 £1,353 £21,657 16.0 yrs £5,395
7 kW 6955 kWh 5355 kWh 1600 kWh £1,418 £160 £1,578 £23,692 15.0 yrs £7,869
8 kW 7948 kWh 6120 kWh 1828 kWh £1,621 £183 £1,803 £25,726 14.3 yrs £10,343

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 SN12

Figures below are tailored to SN12 — click through for full league tables.

Big-Roof Britain Rank #1067 of 2182
5.0 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #881 of 2997
10.7 years (UK avg 11.3 years)
~£947 /yr • £10,173 upfront
Standing-Charge Drag Rank #806 of 2997
17.2% (UK avg 21.7%) drag on savings
£163 fixed • ~£947 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
994kWh/kW
A 1 kW system generates ~994 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: 74% • Flats: 14% • Bungalows: 11% Based on 6,798 properties

Coverage

Wiltshire (100%)

Areas Covered

Melksham South, Melksham Without North & Shurnhold, Melksham Forest, Bowerhill, Melksham East, Melksham Without West & Rural, Devizes Rural West, Holt + 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

SN13 (Wiltshire)
≈7.4 km away
Local sunshine: ~986 kWh/kWp · -1% vs SN12
BA14 (Wiltshire)
≈7.6 km away
Local sunshine: ~1,000 kWh/kWp · +1% vs SN12
BA15 (Wiltshire)
≈8.5 km away
Local sunshine: ~1,001 kWh/kWp · +1% vs SN12
SN14 (Wiltshire)
≈10.2 km away
Local sunshine: ~985 kWh/kWp · -1% vs SN12
SN15 (Wiltshire)
≈10.2 km away
Local sunshine: ~985 kWh/kWp · -1% vs SN12
SN10 (Wiltshire)
≈10.3 km away
Local sunshine: ~999 kWh/kWp · +1% vs SN12

Similar sunshine across the UK

NN2 (West Northamptonshire)
~994 kWh/kWp · -0% vs SN12
NN3 (West Northamptonshire)
~994 kWh/kWp · -0% vs SN12
SE13 (Lewisham)
~993 kWh/kWp · -0% vs SN12