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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in W1U (Westminster)

See if solar pays off for you in Westminster — 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
12.7 years
After this, it's pure profit
Upfront Cost
£6,104
What you pay to get started
Annual Benefit
£482
What you save every year
Profit Over 25 Years
£5,954
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 London, the current unit rate is 25.63p/kWh with a 46.06p/day standing charge. Your postcode’s south-facing sunshine yield is 989 kWh/kW — 1 below the regional median (991).

Read the full story

A typical roof here lands around 3.0 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 25.6p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
25.6p/kWh
Standing charge
46.1p/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: £804, Upfront: £10,173, Break-even: 12.7 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 £203 £119 £322 £4,069 12.7 yrs £2,362
3 kW 2968 kWh 1187 kWh 1781 kWh £304 £178 £482 £6,104 12.7 yrs £3,543
4 kW 3957 kWh 1583 kWh 2374 kWh £406 £237 £643 £8,138 12.7 yrs £4,723
5 kW 4946 kWh 1978 kWh 2968 kWh £507 £297 £804 £10,173 12.7 yrs £5,904
6 kW 5935 kWh 2374 kWh 3561 kWh £608 £356 £965 £12,207 12.7 yrs £7,085
7 kW 6925 kWh 2770 kWh 4155 kWh £710 £415 £1,125 £14,242 12.7 yrs £8,266
8 kW 7914 kWh 3166 kWh 4748 kWh £811 £475 £1,286 £16,276 12.7 yrs £9,447

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: £958, Upfront: £12,273, 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 1187 kWh 791 kWh £304 £79 £383 £6,169 16.1 yrs £1,499
3 kW 2968 kWh 1781 kWh 1187 kWh £456 £119 £575 £8,204 14.3 yrs £3,298
4 kW 3957 kWh 2374 kWh 1583 kWh £608 £158 £767 £10,238 13.4 yrs £5,097
5 kW 4946 kWh 2968 kWh 1978 kWh £761 £198 £958 £12,273 12.8 yrs £6,897
6 kW 5935 kWh 3561 kWh 2374 kWh £913 £237 £1,150 £14,307 12.4 yrs £8,696
7 kW 6925 kWh 4155 kWh 2770 kWh £1,065 £277 £1,342 £16,342 12.2 yrs £10,495
8 kW 7914 kWh 4748 kWh 3166 kWh £1,217 £317 £1,534 £18,376 12.0 yrs £12,294

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: £1,036, Upfront: £13,673, Break-even: 13.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1978 kWh 1385 kWh 594 kWh £355 £59 £414 £7,569 18.3 yrs £717
3 kW 2968 kWh 2077 kWh 890 kWh £532 £89 £621 £9,604 15.5 yrs £2,826
4 kW 3957 kWh 2770 kWh 1187 kWh £710 £119 £829 £11,638 14.0 yrs £4,934
5 kW 4946 kWh 3462 kWh 1484 kWh £887 £148 £1,036 £13,673 13.2 yrs £7,043
6 kW 5935 kWh 4155 kWh 1781 kWh £1,065 £178 £1,243 £15,707 12.6 yrs £9,151
7 kW 6925 kWh 4847 kWh 2077 kWh £1,242 £208 £1,450 £17,742 12.2 yrs £11,260
8 kW 7914 kWh 5540 kWh 2374 kWh £1,420 £237 £1,657 £19,776 11.9 yrs £13,368

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: £1,059, Upfront: £15,423, Break-even: 14.6 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 £370 £53 £424 £9,319 22.0 yrs £-847
3 kW 2968 kWh 2166 kWh 801 kWh £555 £80 £635 £11,354 17.9 yrs £1,354
4 kW 3957 kWh 2889 kWh 1068 kWh £740 £107 £847 £13,388 15.8 yrs £3,555
5 kW 4946 kWh 3611 kWh 1335 kWh £925 £134 £1,059 £15,423 14.6 yrs £5,757
6 kW 5935 kWh 4333 kWh 1603 kWh £1,110 £160 £1,271 £17,457 13.7 yrs £7,958
7 kW 6925 kWh 5055 kWh 1870 kWh £1,296 £187 £1,483 £19,492 13.1 yrs £10,159
8 kW 7914 kWh 5777 kWh 2137 kWh £1,481 £214 £1,694 £21,526 12.7 yrs £12,360

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: £1,074, Upfront: £17,173, Break-even: 16.0 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 £380 £49 £430 £11,069 25.8 yrs £-2,474
3 kW 2968 kWh 2226 kWh 742 kWh £570 £74 £645 £13,104 20.3 yrs £-211
4 kW 3957 kWh 2968 kWh 989 kWh £761 £99 £860 £15,138 17.6 yrs £2,053
5 kW 4946 kWh 3710 kWh 1237 kWh £951 £124 £1,074 £17,173 16.0 yrs £4,316
6 kW 5935 kWh 4451 kWh 1484 kWh £1,141 £148 £1,289 £19,207 14.9 yrs £6,579
7 kW 6925 kWh 5193 kWh 1731 kWh £1,331 £173 £1,504 £21,242 14.1 yrs £8,842
8 kW 7914 kWh 5935 kWh 1978 kWh £1,521 £198 £1,719 £23,276 13.5 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.

13.5 kWh battery 5 kW example → Annual benefit: £1,090, Upfront: £19,623, Break-even: 18.0 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 £390 £46 £436 £13,519 31.0 yrs £-4,800
3 kW 2968 kWh 2285 kWh 683 kWh £586 £68 £654 £15,554 23.8 yrs £-2,475
4 kW 3957 kWh 3047 kWh 910 kWh £781 £91 £872 £17,588 20.2 yrs £-150
5 kW 4946 kWh 3808 kWh 1138 kWh £976 £114 £1,090 £19,623 18.0 yrs £2,175
6 kW 5935 kWh 4570 kWh 1365 kWh £1,171 £137 £1,308 £21,657 16.6 yrs £4,500
7 kW 6925 kWh 5332 kWh 1593 kWh £1,367 £159 £1,526 £23,692 15.5 yrs £6,825
8 kW 7914 kWh 6094 kWh 1820 kWh £1,562 £182 £1,744 £25,726 14.8 yrs £9,150

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 W1U

Figures below are tailored to W1U — click through for full league tables.

Solar Payback Index Rank #1481 of 2997
11.1 years (UK avg 11.3 years)
~£1,104 /yr • £12,207 upfront
Standing-Charge Drag Rank #305 of 2997
15.2% (UK avg 21.7%) drag on savings
£168 fixed • ~£1,104 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/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
3.0kW
For eligible homes in this area

⚠️ This area is predominantly flats. Many residents require freeholder approval for solar installations. System size shown reflects houses and bungalows only.

Local Property Data

Property Types

Houses: 5% • Flats: 91% • Bungalows: 0% Based on 3,666 properties

Coverage

Westminster (100%)

Areas Covered

Marylebone, West End, Clerkenwell

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 London

W1 (Westminster)
≈0.1 km away
Local sunshine: ~989 kWh/kWp · +0% vs W1U
W1M (Westminster)
≈0.2 km away
Local sunshine: ~988 kWh/kWp · -0% vs W1U
W1G (Westminster)
≈0.3 km away
Local sunshine: ~988 kWh/kWp · -0% vs W1U
W1H (Westminster)
≈0.5 km away
Local sunshine: ~989 kWh/kWp · +0% vs W1U
W1C (Westminster)
≈0.5 km away
Local sunshine: ~988 kWh/kWp · -0% vs W1U
W1N (Westminster)
≈0.7 km away
Local sunshine: ~988 kWh/kWp · -0% vs W1U

Similar sunshine across the UK

BS16 (South Gloucestershire)
~989 kWh/kWp · -0% vs W1U
LL64 (Isle of Anglesey)
~989 kWh/kWp · +0% vs W1U
BS15 (South Gloucestershire)
~989 kWh/kWp · -0% vs W1U