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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SP3 (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
11.9 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£1,027
What you save every year
Profit Over 25 Years
£13,463
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 1031 kWh/kW — 30 above the regional median (1001).

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 1031 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)
1031 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: £856, Upfront: £10,173, 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 2063 kWh 825 kWh 1238 kWh £218 £124 £342 £4,069 11.9 yrs £2,776
3 kW 3094 kWh 1238 kWh 1857 kWh £328 £186 £513 £6,104 11.9 yrs £4,165
4 kW 4126 kWh 1650 kWh 2475 kWh £437 £248 £685 £8,138 11.9 yrs £5,553
5 kW 5157 kWh 2063 kWh 3094 kWh £546 £309 £856 £10,173 11.9 yrs £6,941
6 kW 6189 kWh 2475 kWh 3713 kWh £655 £371 £1,027 £12,207 11.9 yrs £8,329
7 kW 7220 kWh 2888 kWh 4332 kWh £765 £433 £1,198 £14,242 11.9 yrs £9,717
8 kW 8251 kWh 3301 kWh 4951 kWh £874 £495 £1,369 £16,276 11.9 yrs £11,105

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: £1,026, Upfront: £12,273, Break-even: 12.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2063 kWh 1238 kWh 825 kWh £328 £83 £410 £6,169 15.0 yrs £2,036
3 kW 3094 kWh 1857 kWh 1238 kWh £492 £124 £615 £8,204 13.3 yrs £4,104
4 kW 4126 kWh 2475 kWh 1650 kWh £655 £165 £821 £10,238 12.5 yrs £6,172
5 kW 5157 kWh 3094 kWh 2063 kWh £819 £206 £1,026 £12,273 12.0 yrs £8,241
6 kW 6189 kWh 3713 kWh 2475 kWh £983 £248 £1,231 £14,307 11.6 yrs £10,309
7 kW 7220 kWh 4332 kWh 2888 kWh £1,147 £289 £1,436 £16,342 11.4 yrs £12,377
8 kW 8251 kWh 4951 kWh 3301 kWh £1,311 £330 £1,641 £18,376 11.2 yrs £14,445

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: £1,111, Upfront: £13,673, 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 2063 kWh 1444 kWh 619 kWh £382 £62 £444 £7,569 17.0 yrs £1,316
3 kW 3094 kWh 2166 kWh 928 kWh £574 £93 £666 £9,604 14.4 yrs £3,724
4 kW 4126 kWh 2888 kWh 1238 kWh £765 £124 £889 £11,638 13.1 yrs £6,132
5 kW 5157 kWh 3610 kWh 1547 kWh £956 £155 £1,111 £13,673 12.3 yrs £8,540
6 kW 6189 kWh 4332 kWh 1857 kWh £1,147 £186 £1,333 £15,707 11.8 yrs £10,948
7 kW 7220 kWh 5054 kWh 2166 kWh £1,338 £217 £1,555 £17,742 11.4 yrs £13,356
8 kW 8251 kWh 5776 kWh 2475 kWh £1,529 £248 £1,777 £19,776 11.1 yrs £15,765

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: £1,136, Upfront: £15,423, Break-even: 13.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2063 kWh 1506 kWh 557 kWh £399 £56 £454 £9,319 20.5 yrs £-230
3 kW 3094 kWh 2259 kWh 835 kWh £598 £84 £682 £11,354 16.7 yrs £2,280
4 kW 4126 kWh 3012 kWh 1114 kWh £798 £111 £909 £13,388 14.7 yrs £4,790
5 kW 5157 kWh 3765 kWh 1392 kWh £997 £139 £1,136 £15,423 13.6 yrs £7,300
6 kW 6189 kWh 4518 kWh 1671 kWh £1,196 £167 £1,363 £17,457 12.8 yrs £9,810
7 kW 7220 kWh 5271 kWh 1949 kWh £1,396 £195 £1,591 £19,492 12.3 yrs £12,320
8 kW 8251 kWh 6024 kWh 2228 kWh £1,595 £223 £1,818 £21,526 11.8 yrs £14,830

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: £1,153, Upfront: £17,173, Break-even: 14.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2063 kWh 1547 kWh 516 kWh £410 £52 £461 £11,069 24.0 yrs £-1,844
3 kW 3094 kWh 2321 kWh 774 kWh £615 £77 £692 £13,104 18.9 yrs £734
4 kW 4126 kWh 3094 kWh 1031 kWh £819 £103 £923 £15,138 16.4 yrs £3,312
5 kW 5157 kWh 3868 kWh 1289 kWh £1,024 £129 £1,153 £17,173 14.9 yrs £5,890
6 kW 6189 kWh 4641 kWh 1547 kWh £1,229 £155 £1,384 £19,207 13.9 yrs £8,468
7 kW 7220 kWh 5415 kWh 1805 kWh £1,434 £181 £1,614 £21,242 13.2 yrs £11,046
8 kW 8251 kWh 6189 kWh 2063 kWh £1,639 £206 £1,845 £23,276 12.6 yrs £13,624

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: £1,170, Upfront: £19,623, Break-even: 16.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2063 kWh 1588 kWh 474 kWh £421 £47 £468 £13,519 28.9 yrs £-4,158
3 kW 3094 kWh 2383 kWh 712 kWh £631 £71 £702 £15,554 22.2 yrs £-1,512
4 kW 4126 kWh 3177 kWh 949 kWh £841 £95 £936 £17,588 18.8 yrs £1,134
5 kW 5157 kWh 3971 kWh 1186 kWh £1,052 £119 £1,170 £19,623 16.8 yrs £3,780
6 kW 6189 kWh 4765 kWh 1423 kWh £1,262 £142 £1,404 £21,657 15.4 yrs £6,426
7 kW 7220 kWh 5559 kWh 1661 kWh £1,472 £166 £1,638 £23,692 14.5 yrs £9,072
8 kW 8251 kWh 6354 kWh 1898 kWh £1,682 £190 £1,872 £25,726 13.7 yrs £11,718

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 SP3

Figures below are tailored to SP3 — click through for full league tables.

Big-Roof Britain Rank #225 of 2182
6.1 kWp (UK avg 5.1 kWp)
~13 panels (≈430 W)
Solar Payback Index Rank #357 of 2997
10.3 years (UK avg 11.3 years)
~£1,180 /yr • £12,207 upfront
Standing-Charge Drag Rank #75 of 2997
13.8% (UK avg 21.7%) drag on savings
£163 fixed • ~£1,180 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
1031kWh/kW
A 1 kW system generates ~1031 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: 70% • Flats: 6% • Bungalows: 24% Based on 3,436 properties

Coverage

Wiltshire (100%)

Areas Covered

Nadder Valley, Tisbury, Till Valley, Fovant & Chalke Valley, Salisbury St Edmund's, Wylye Valley, Amesbury West

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

SP2 (Wiltshire)
≈14.6 km away
Local sunshine: ~1,028 kWh/kWp · -0% vs SP3
SP7 (Dorset)
≈14.6 km away
Local sunshine: ~1,004 kWh/kWp · -3% vs SP3
SP1 (Wiltshire)
≈15.7 km away
Local sunshine: ~1,019 kWh/kWp · -1% vs SP3
BA12 (Wiltshire)
≈17.6 km away
Local sunshine: ~1,011 kWh/kWp · -2% vs SP3
SP8 (Dorset)
≈18.9 km away
Local sunshine: ~1,013 kWh/kWp · -2% vs SP3
SP4 (Wiltshire)
≈19.9 km away
Local sunshine: ~1,018 kWh/kWp · -1% vs SP3

Similar sunshine across the UK

EX3 (Exeter)
~1,031 kWh/kWp · +0% vs SP3
TQ13 (Teignbridge)
~1,031 kWh/kWp · -0% vs SP3
CF32 (Bridgend)
~1,031 kWh/kWp · -0% vs SP3