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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in W1Y (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
£12,207
What you pay to get started
Annual Benefit
£963
What you save every year
Profit Over 25 Years
£11,864
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 987 kWh/kW — 3 below the regional median (991).

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 987 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)
987 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: £802, 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 1975 kWh 790 kWh 1185 kWh £202 £118 £321 £4,069 12.7 yrs £2,350
3 kW 2962 kWh 1185 kWh 1777 kWh £304 £178 £481 £6,104 12.7 yrs £3,525
4 kW 3950 kWh 1580 kWh 2370 kWh £405 £237 £642 £8,138 12.7 yrs £4,700
5 kW 4937 kWh 1975 kWh 2962 kWh £506 £296 £802 £10,173 12.7 yrs £5,875
6 kW 5924 kWh 2370 kWh 3555 kWh £607 £355 £963 £12,207 12.7 yrs £7,050
7 kW 6912 kWh 2765 kWh 4147 kWh £709 £415 £1,123 £14,242 12.7 yrs £8,225
8 kW 7899 kWh 3160 kWh 4740 kWh £810 £474 £1,284 £16,276 12.7 yrs £9,399

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: £957, 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 1975 kWh 1185 kWh 790 kWh £304 £79 £383 £6,169 16.1 yrs £1,485
3 kW 2962 kWh 1777 kWh 1185 kWh £456 £118 £574 £8,204 14.3 yrs £3,277
4 kW 3950 kWh 2370 kWh 1580 kWh £607 £158 £765 £10,238 13.4 yrs £5,069
5 kW 4937 kWh 2962 kWh 1975 kWh £759 £197 £957 £12,273 12.8 yrs £6,861
6 kW 5924 kWh 3555 kWh 2370 kWh £911 £237 £1,148 £14,307 12.5 yrs £8,654
7 kW 6912 kWh 4147 kWh 2765 kWh £1,063 £276 £1,339 £16,342 12.2 yrs £10,446
8 kW 7899 kWh 4740 kWh 3160 kWh £1,215 £316 £1,531 £18,376 12.0 yrs £12,238

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: £1,034, 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 1975 kWh 1382 kWh 592 kWh £354 £59 £414 £7,569 18.3 yrs £702
3 kW 2962 kWh 2074 kWh 889 kWh £531 £89 £620 £9,604 15.5 yrs £2,803
4 kW 3950 kWh 2765 kWh 1185 kWh £709 £118 £827 £11,638 14.1 yrs £4,904
5 kW 4937 kWh 3456 kWh 1481 kWh £886 £148 £1,034 £13,673 13.2 yrs £7,005
6 kW 5924 kWh 4147 kWh 1777 kWh £1,063 £178 £1,241 £15,707 12.7 yrs £9,106
7 kW 6912 kWh 4838 kWh 2074 kWh £1,240 £207 £1,447 £17,742 12.3 yrs £11,206
8 kW 7899 kWh 5529 kWh 2370 kWh £1,417 £237 £1,654 £19,776 12.0 yrs £13,307

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: £1,057, 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 1975 kWh 1442 kWh 533 kWh £369 £53 £423 £9,319 22.0 yrs £-863
3 kW 2962 kWh 2162 kWh 800 kWh £554 £80 £634 £11,354 17.9 yrs £1,331
4 kW 3950 kWh 2883 kWh 1066 kWh £739 £107 £846 £13,388 15.8 yrs £3,524
5 kW 4937 kWh 3604 kWh 1333 kWh £924 £133 £1,057 £15,423 14.6 yrs £5,718
6 kW 5924 kWh 4325 kWh 1600 kWh £1,108 £160 £1,268 £17,457 13.8 yrs £7,911
7 kW 6912 kWh 5046 kWh 1866 kWh £1,293 £187 £1,480 £19,492 13.2 yrs £10,105
8 kW 7899 kWh 5766 kWh 2133 kWh £1,478 £213 £1,691 £21,526 12.7 yrs £12,298

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: £1,072, 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 1975 kWh 1481 kWh 494 kWh £380 £49 £429 £11,069 25.8 yrs £-2,490
3 kW 2962 kWh 2222 kWh 741 kWh £569 £74 £643 £13,104 20.4 yrs £-234
4 kW 3950 kWh 2962 kWh 987 kWh £759 £99 £858 £15,138 17.6 yrs £2,021
5 kW 4937 kWh 3703 kWh 1234 kWh £949 £123 £1,072 £17,173 16.0 yrs £4,276
6 kW 5924 kWh 4443 kWh 1481 kWh £1,139 £148 £1,287 £19,207 14.9 yrs £6,531
7 kW 6912 kWh 5184 kWh 1728 kWh £1,329 £173 £1,501 £21,242 14.1 yrs £8,787
8 kW 7899 kWh 5924 kWh 1975 kWh £1,518 £197 £1,716 £23,276 13.6 yrs £11,042

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: £1,088, 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 1975 kWh 1521 kWh 454 kWh £390 £45 £435 £13,519 31.1 yrs £-4,816
3 kW 2962 kWh 2281 kWh 681 kWh £585 £68 £653 £15,554 23.8 yrs £-2,499
4 kW 3950 kWh 3041 kWh 908 kWh £779 £91 £870 £17,588 20.2 yrs £-182
5 kW 4937 kWh 3801 kWh 1136 kWh £974 £114 £1,088 £19,623 18.0 yrs £2,135
6 kW 5924 kWh 4562 kWh 1363 kWh £1,169 £136 £1,305 £21,657 16.6 yrs £4,452
7 kW 6912 kWh 5322 kWh 1590 kWh £1,364 £159 £1,523 £23,692 15.6 yrs £6,769
8 kW 7899 kWh 6082 kWh 1817 kWh £1,559 £182 £1,741 £25,726 14.8 yrs £9,086

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 W1Y

Figures below are tailored to W1Y — click through for full league tables.

Solar Payback Index Rank #1485 of 2997
11.1 years (UK avg 11.3 years)
~£1,102 /yr • £12,207 upfront
Standing-Charge Drag Rank #397 of 2997
15.3% (UK avg 21.7%) drag on savings
£168 fixed • ~£1,102 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
987kWh/kW
A 1 kW system generates ~987 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

No EPC data available for this outcode

Coverage

Westminster (100%)

Areas Covered

West End, Hyde Park

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

W1K (Westminster)
≈0.1 km away
Local sunshine: ~989 kWh/kWp · +0% vs W1Y
W1J (Westminster)
≈0.4 km away
Local sunshine: ~987 kWh/kWp · +0% vs W1Y
W1X (Westminster)
≈0.4 km away
Local sunshine: ~988 kWh/kWp · +0% vs W1Y
W1C (Westminster)
≈0.4 km away
Local sunshine: ~988 kWh/kWp · +0% vs W1Y
W1S (Westminster)
≈0.5 km away
Local sunshine: ~988 kWh/kWp · +0% vs W1Y
W1R (Westminster)
≈0.6 km away
Local sunshine: ~988 kWh/kWp · +0% vs W1Y

Similar sunshine across the UK

PL15 (Cornwall)
~987 kWh/kWp · +0% vs W1Y
HP12 (Buckinghamshire)
~987 kWh/kWp · +0% vs W1Y
LU7 (Central Bedfordshire)
~987 kWh/kWp · -0% vs W1Y