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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SP4 (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
12.0 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£845
What you save every year
Profit Over 25 Years
£10,949
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 1018 kWh/kW — 17 above 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 1018 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)
1018 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: £845, Upfront: £10,173, 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 2037 kWh 815 kWh 1222 kWh £216 £122 £338 £4,069 12.0 yrs £2,690
3 kW 3055 kWh 1222 kWh 1833 kWh £324 £183 £507 £6,104 12.0 yrs £4,035
4 kW 4074 kWh 1629 kWh 2444 kWh £431 £244 £676 £8,138 12.0 yrs £5,380
5 kW 5092 kWh 2037 kWh 3055 kWh £539 £306 £845 £10,173 12.0 yrs £6,725
6 kW 6110 kWh 2444 kWh 3666 kWh £647 £367 £1,014 £12,207 12.0 yrs £8,070
7 kW 7129 kWh 2852 kWh 4277 kWh £755 £428 £1,183 £14,242 12.0 yrs £9,415
8 kW 8147 kWh 3259 kWh 4888 kWh £863 £489 £1,352 £16,276 12.0 yrs £10,760

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: £1,013, Upfront: £12,273, Break-even: 12.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2037 kWh 1222 kWh 815 kWh £324 £81 £405 £6,169 15.2 yrs £1,933
3 kW 3055 kWh 1833 kWh 1222 kWh £485 £122 £608 £8,204 13.5 yrs £3,949
4 kW 4074 kWh 2444 kWh 1629 kWh £647 £163 £810 £10,238 12.6 yrs £5,965
5 kW 5092 kWh 3055 kWh 2037 kWh £809 £204 £1,013 £12,273 12.1 yrs £7,982
6 kW 6110 kWh 3666 kWh 2444 kWh £971 £244 £1,215 £14,307 11.8 yrs £9,998
7 kW 7129 kWh 4277 kWh 2852 kWh £1,133 £285 £1,418 £16,342 11.5 yrs £12,014
8 kW 8147 kWh 4888 kWh 3259 kWh £1,294 £326 £1,620 £18,376 11.3 yrs £14,031

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: £1,097, Upfront: £13,673, 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 2037 kWh 1426 kWh 611 kWh £378 £61 £439 £7,569 17.3 yrs £1,204
3 kW 3055 kWh 2139 kWh 917 kWh £566 £92 £658 £9,604 14.6 yrs £3,556
4 kW 4074 kWh 2852 kWh 1222 kWh £755 £122 £877 £11,638 13.3 yrs £5,908
5 kW 5092 kWh 3564 kWh 1528 kWh £944 £153 £1,097 £13,673 12.5 yrs £8,260
6 kW 6110 kWh 4277 kWh 1833 kWh £1,133 £183 £1,316 £15,707 11.9 yrs £10,612
7 kW 7129 kWh 4990 kWh 2139 kWh £1,321 £214 £1,535 £17,742 11.6 yrs £12,964
8 kW 8147 kWh 5703 kWh 2444 kWh £1,510 £244 £1,755 £19,776 11.3 yrs £15,316

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: £1,122, Upfront: £15,423, Break-even: 13.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2037 kWh 1487 kWh 550 kWh £394 £55 £449 £9,319 20.8 yrs £-345
3 kW 3055 kWh 2230 kWh 825 kWh £591 £82 £673 £11,354 16.9 yrs £2,108
4 kW 4074 kWh 2974 kWh 1100 kWh £787 £110 £897 £13,388 14.9 yrs £4,561
5 kW 5092 kWh 3717 kWh 1375 kWh £984 £137 £1,122 £15,423 13.7 yrs £7,013
6 kW 6110 kWh 4461 kWh 1650 kWh £1,181 £165 £1,346 £17,457 13.0 yrs £9,466
7 kW 7129 kWh 5204 kWh 1925 kWh £1,378 £192 £1,571 £19,492 12.4 yrs £11,919
8 kW 8147 kWh 5948 kWh 2200 kWh £1,575 £220 £1,795 £21,526 12.0 yrs £14,371

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: £1,139, Upfront: £17,173, Break-even: 15.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2037 kWh 1528 kWh 509 kWh £405 £51 £455 £11,069 24.3 yrs £-1,960
3 kW 3055 kWh 2291 kWh 764 kWh £607 £76 £683 £13,104 19.2 yrs £559
4 kW 4074 kWh 3055 kWh 1018 kWh £809 £102 £911 £15,138 16.6 yrs £3,079
5 kW 5092 kWh 3819 kWh 1273 kWh £1,011 £127 £1,139 £17,173 15.1 yrs £5,599
6 kW 6110 kWh 4583 kWh 1528 kWh £1,214 £153 £1,366 £19,207 14.1 yrs £8,119
7 kW 7129 kWh 5347 kWh 1782 kWh £1,416 £178 £1,594 £21,242 13.3 yrs £10,639
8 kW 8147 kWh 6110 kWh 2037 kWh £1,618 £204 £1,822 £23,276 12.8 yrs £13,159

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: £1,155, Upfront: £19,623, Break-even: 17.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2037 kWh 1568 kWh 468 kWh £415 £47 £462 £13,519 29.3 yrs £-4,276
3 kW 3055 kWh 2353 kWh 703 kWh £623 £70 £693 £15,554 22.4 yrs £-1,689
4 kW 4074 kWh 3137 kWh 937 kWh £831 £94 £924 £17,588 19.0 yrs £898
5 kW 5092 kWh 3921 kWh 1171 kWh £1,038 £117 £1,155 £19,623 17.0 yrs £3,485
6 kW 6110 kWh 4705 kWh 1405 kWh £1,246 £141 £1,386 £21,657 15.6 yrs £6,072
7 kW 7129 kWh 5489 kWh 1640 kWh £1,454 £164 £1,618 £23,692 14.6 yrs £8,659
8 kW 8147 kWh 6273 kWh 1874 kWh £1,661 £187 £1,849 £25,726 13.9 yrs £11,246

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 SP4

Figures below are tailored to SP4 — click through for full league tables.

Big-Roof Britain Rank #702 of 2182
5.4 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #581 of 2997
10.5 years (UK avg 11.3 years)
~£971 /yr • £10,173 upfront
Standing-Charge Drag Rank #683 of 2997
16.8% (UK avg 21.7%) drag on savings
£163 fixed • ~£971 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
1018kWh/kW
A 1 kW system generates ~1018 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: 78% • Flats: 11% • Bungalows: 11% Based on 11,480 properties

Coverage

Wiltshire (99%)|Test Valley (1%)

Areas Covered

Amesbury East & Bulford, Old Sarum & Lower Bourne Valley, Amesbury West, Avon Valley, Winterslow & Upper Bourne Valley, Durrington, Amesbury South, Salisbury St Edmund's + 4 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

SP9 (Wiltshire)
≈10.3 km away
Local sunshine: ~1,016 kWh/kWp · -0% vs SP4
SP1 (Wiltshire)
≈11.2 km away
Local sunshine: ~1,019 kWh/kWp · +0% vs SP4
SP2 (Wiltshire)
≈11.4 km away
Local sunshine: ~1,028 kWh/kWp · +1% vs SP4
SP5 (Wiltshire)
≈16.1 km away
Local sunshine: ~1,019 kWh/kWp · +0% vs SP4
SN9 (Wiltshire)
≈18.7 km away
Local sunshine: ~989 kWh/kWp · -3% vs SP4
SP11 (Test Valley)
≈19.3 km away
Local sunshine: ~1,005 kWh/kWp · -1% vs SP4

Similar sunshine across the UK

ME7 (Medway)
~1,018 kWh/kWp · -0% vs SP4
TA14 (Somerset)
~1,018 kWh/kWp · -0% vs SP4
NR26 (North Norfolk)
~1,019 kWh/kWp · +0% vs SP4