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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SE18 (Greenwich)

See if solar pays off for you in Greenwich — 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
12.4 years
After this, it's pure profit
Upfront Cost
£6,104
What you pay to get started
Annual Benefit
£493
What you save every year
Profit Over 25 Years
£6,215
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 1011 kWh/kW — 20 above 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 1011 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)
1011 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: £821, Upfront: £10,173, 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 2021 kWh 809 kWh 1213 kWh £207 £121 £328 £4,069 12.4 yrs £2,501
3 kW 3032 kWh 1213 kWh 1819 kWh £311 £182 £493 £6,104 12.4 yrs £3,751
4 kW 4043 kWh 1617 kWh 2426 kWh £414 £243 £657 £8,138 12.4 yrs £5,002
5 kW 5053 kWh 2021 kWh 3032 kWh £518 £303 £821 £10,173 12.4 yrs £6,252
6 kW 6064 kWh 2426 kWh 3638 kWh £622 £364 £985 £12,207 12.4 yrs £7,503
7 kW 7074 kWh 2830 kWh 4245 kWh £725 £424 £1,150 £14,242 12.4 yrs £8,753
8 kW 8085 kWh 3234 kWh 4851 kWh £829 £485 £1,314 £16,276 12.4 yrs £10,004

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: £979, Upfront: £12,273, 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 2021 kWh 1213 kWh 809 kWh £311 £81 £392 £6,169 15.8 yrs £1,665
3 kW 3032 kWh 1819 kWh 1213 kWh £466 £121 £588 £8,204 14.0 yrs £3,547
4 kW 4043 kWh 2426 kWh 1617 kWh £622 £162 £783 £10,238 13.1 yrs £5,429
5 kW 5053 kWh 3032 kWh 2021 kWh £777 £202 £979 £12,273 12.5 yrs £7,312
6 kW 6064 kWh 3638 kWh 2426 kWh £932 £243 £1,175 £14,307 12.2 yrs £9,194
7 kW 7074 kWh 4245 kWh 2830 kWh £1,088 £283 £1,371 £16,342 11.9 yrs £11,076
8 kW 8085 kWh 4851 kWh 3234 kWh £1,243 £323 £1,567 £18,376 11.7 yrs £12,959

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: £1,058, Upfront: £13,673, Break-even: 12.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2021 kWh 1415 kWh 606 kWh £363 £61 £423 £7,569 17.9 yrs £897
3 kW 3032 kWh 2122 kWh 910 kWh £544 £91 £635 £9,604 15.1 yrs £3,095
4 kW 4043 kWh 2830 kWh 1213 kWh £725 £121 £847 £11,638 13.7 yrs £5,293
5 kW 5053 kWh 3537 kWh 1516 kWh £907 £152 £1,058 £13,673 12.9 yrs £7,491
6 kW 6064 kWh 4245 kWh 1819 kWh £1,088 £182 £1,270 £15,707 12.4 yrs £9,690
7 kW 7074 kWh 4952 kWh 2122 kWh £1,269 £212 £1,481 £17,742 12.0 yrs £11,888
8 kW 8085 kWh 5660 kWh 2426 kWh £1,451 £243 £1,693 £19,776 11.7 yrs £14,086

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: £1,082, Upfront: £15,423, Break-even: 14.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2021 kWh 1476 kWh 546 kWh £378 £55 £433 £9,319 21.5 yrs £-664
3 kW 3032 kWh 2213 kWh 819 kWh £567 £82 £649 £11,354 17.5 yrs £1,629
4 kW 4043 kWh 2951 kWh 1091 kWh £756 £109 £866 £13,388 15.5 yrs £3,922
5 kW 5053 kWh 3689 kWh 1364 kWh £945 £136 £1,082 £15,423 14.3 yrs £6,215
6 kW 6064 kWh 4427 kWh 1637 kWh £1,135 £164 £1,298 £17,457 13.4 yrs £8,508
7 kW 7074 kWh 5164 kWh 1910 kWh £1,324 £191 £1,515 £19,492 12.9 yrs £10,801
8 kW 8085 kWh 5902 kWh 2183 kWh £1,513 £218 £1,731 £21,526 12.4 yrs £13,094

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: £1,098, Upfront: £17,173, Break-even: 15.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2021 kWh 1516 kWh 505 kWh £389 £51 £439 £11,069 25.2 yrs £-2,288
3 kW 3032 kWh 2274 kWh 758 kWh £583 £76 £659 £13,104 19.9 yrs £69
4 kW 4043 kWh 3032 kWh 1011 kWh £777 £101 £878 £15,138 17.2 yrs £2,425
5 kW 5053 kWh 3790 kWh 1263 kWh £971 £126 £1,098 £17,173 15.6 yrs £4,781
6 kW 6064 kWh 4548 kWh 1516 kWh £1,166 £152 £1,317 £19,207 14.6 yrs £7,137
7 kW 7074 kWh 5306 kWh 1769 kWh £1,360 £177 £1,537 £21,242 13.8 yrs £9,494
8 kW 8085 kWh 6064 kWh 2021 kWh £1,554 £202 £1,756 £23,276 13.3 yrs £11,850

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: £1,113, Upfront: £19,623, Break-even: 17.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2021 kWh 1556 kWh 465 kWh £399 £46 £445 £13,519 30.4 yrs £-4,611
3 kW 3032 kWh 2335 kWh 697 kWh £598 £70 £668 £15,554 23.3 yrs £-2,192
4 kW 4043 kWh 3113 kWh 930 kWh £798 £93 £891 £17,588 19.7 yrs £228
5 kW 5053 kWh 3891 kWh 1162 kWh £997 £116 £1,113 £19,623 17.6 yrs £2,647
6 kW 6064 kWh 4669 kWh 1395 kWh £1,197 £139 £1,336 £21,657 16.2 yrs £5,066
7 kW 7074 kWh 5447 kWh 1627 kWh £1,396 £163 £1,559 £23,692 15.2 yrs £7,486
8 kW 8085 kWh 6226 kWh 1860 kWh £1,596 £186 £1,782 £25,726 14.4 yrs £9,905

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 SE18

Figures below are tailored to SE18 — click through for full league tables.

Big-Roof Britain Rank #2063 of 2182
4.0 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #1060 of 2997
10.8 years (UK avg 11.3 years)
~£940 /yr • £10,173 upfront
Standing-Charge Drag Rank #970 of 2997
17.9% (UK avg 21.7%) drag on savings
£168 fixed • ~£940 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
1011kWh/kW
A 1 kW system generates ~1011 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
3.0kW
For houses & bungalows 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: 31% • Flats: 65% • Bungalows: 0% Based on 25,260 properties

Coverage

Greenwich (100%)

Areas Covered

Woolwich Arsenal, Plumstead & Glyndon, Shooters Hill, Woolwich Common, Plumstead Common, Woolwich Dockyard, West Thamesmead, Charlton Hornfair + 2 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 London

SE7 (Greenwich)
≈2.6 km away
Local sunshine: ~1,006 kWh/kWp · -0% vs SE18
SE28 (Greenwich)
≈2.8 km away
Local sunshine: ~1,010 kWh/kWp · -0% vs SE18
SE2 (Greenwich)
≈3.3 km away
Local sunshine: ~1,016 kWh/kWp · +1% vs SE18
DA16 (Bexley)
≈3.9 km away
Local sunshine: ~1,016 kWh/kWp · +1% vs SE18
E6 (Newham)
≈4.2 km away
Local sunshine: ~1,004 kWh/kWp · -1% vs SE18
E16 (Newham)
≈4.2 km away
Local sunshine: ~1,004 kWh/kWp · -1% vs SE18

Similar sunshine across the UK

BA12 (Wiltshire)
~1,011 kWh/kWp · -0% vs SE18
CF72 (Rhondda Cynon Taf)
~1,011 kWh/kWp · -0% vs SE18
BR5 (Bromley)
~1,011 kWh/kWp · -0% vs SE18