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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SW2 (Lambeth)

See if solar pays off for you in Lambeth — 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
12.6 years
After this, it's pure profit
Upfront Cost
£6,104
What you pay to get started
Annual Benefit
£483
What you save every year
Profit Over 25 Years
£5,968
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 990 kWh/kW — 0 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 990 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)
990 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: £805, Upfront: £10,173, Break-even: 12.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1981 kWh 792 kWh 1188 kWh £203 £119 £322 £4,069 12.6 yrs £2,369
3 kW 2971 kWh 1188 kWh 1783 kWh £305 £178 £483 £6,104 12.6 yrs £3,554
4 kW 3962 kWh 1585 kWh 2377 kWh £406 £238 £644 £8,138 12.6 yrs £4,738
5 kW 4952 kWh 1981 kWh 2971 kWh £508 £297 £805 £10,173 12.6 yrs £5,923
6 kW 5942 kWh 2377 kWh 3565 kWh £609 £357 £966 £12,207 12.6 yrs £7,108
7 kW 6933 kWh 2773 kWh 4160 kWh £711 £416 £1,127 £14,242 12.6 yrs £8,292
8 kW 7923 kWh 3169 kWh 4754 kWh £812 £475 £1,288 £16,276 12.6 yrs £9,477

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: £960, 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 1981 kWh 1188 kWh 792 kWh £305 £79 £384 £6,169 16.1 yrs £1,508
3 kW 2971 kWh 1783 kWh 1188 kWh £457 £119 £576 £8,204 14.2 yrs £3,311
4 kW 3962 kWh 2377 kWh 1585 kWh £609 £158 £768 £10,238 13.3 yrs £5,115
5 kW 4952 kWh 2971 kWh 1981 kWh £762 £198 £960 £12,273 12.8 yrs £6,919
6 kW 5942 kWh 3565 kWh 2377 kWh £914 £238 £1,151 £14,307 12.4 yrs £8,723
7 kW 6933 kWh 4160 kWh 2773 kWh £1,066 £277 £1,343 £16,342 12.2 yrs £10,527
8 kW 7923 kWh 4754 kWh 3169 kWh £1,218 £317 £1,535 £18,376 12.0 yrs £12,330

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: £1,037, 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 1981 kWh 1387 kWh 594 kWh £355 £59 £415 £7,569 18.2 yrs £727
3 kW 2971 kWh 2080 kWh 891 kWh £533 £89 £622 £9,604 15.4 yrs £2,840
4 kW 3962 kWh 2773 kWh 1188 kWh £711 £119 £830 £11,638 14.0 yrs £4,954
5 kW 4952 kWh 3466 kWh 1486 kWh £888 £149 £1,037 £13,673 13.2 yrs £7,067
6 kW 5942 kWh 4160 kWh 1783 kWh £1,066 £178 £1,244 £15,707 12.6 yrs £9,180
7 kW 6933 kWh 4853 kWh 2080 kWh £1,244 £208 £1,452 £17,742 12.2 yrs £11,294
8 kW 7923 kWh 5546 kWh 2377 kWh £1,421 £238 £1,659 £19,776 11.9 yrs £13,407

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: £1,060, Upfront: £15,423, Break-even: 14.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1981 kWh 1446 kWh 535 kWh £371 £53 £424 £9,319 22.0 yrs £-837
3 kW 2971 kWh 2169 kWh 802 kWh £556 £80 £636 £11,354 17.8 yrs £1,369
4 kW 3962 kWh 2892 kWh 1070 kWh £741 £107 £848 £13,388 15.8 yrs £3,575
5 kW 4952 kWh 3615 kWh 1337 kWh £926 £134 £1,060 £15,423 14.5 yrs £5,781
6 kW 5942 kWh 4338 kWh 1604 kWh £1,112 £160 £1,272 £17,457 13.7 yrs £7,988
7 kW 6933 kWh 5061 kWh 1872 kWh £1,297 £187 £1,484 £19,492 13.1 yrs £10,194
8 kW 7923 kWh 5784 kWh 2139 kWh £1,482 £214 £1,696 £21,526 12.7 yrs £12,400

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: £1,076, 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 1981 kWh 1486 kWh 495 kWh £381 £50 £430 £11,069 25.7 yrs £-2,464
3 kW 2971 kWh 2228 kWh 743 kWh £571 £74 £645 £13,104 20.3 yrs £-195
4 kW 3962 kWh 2971 kWh 990 kWh £762 £99 £861 £15,138 17.6 yrs £2,073
5 kW 4952 kWh 3714 kWh 1238 kWh £952 £124 £1,076 £17,173 16.0 yrs £4,341
6 kW 5942 kWh 4457 kWh 1486 kWh £1,142 £149 £1,291 £19,207 14.9 yrs £6,609
7 kW 6933 kWh 5199 kWh 1733 kWh £1,333 £173 £1,506 £21,242 14.1 yrs £8,877
8 kW 7923 kWh 5942 kWh 1981 kWh £1,523 £198 £1,721 £23,276 13.5 yrs £11,146

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: £1,091, 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 1981 kWh 1525 kWh 456 kWh £391 £46 £436 £13,519 31.0 yrs £-4,790
3 kW 2971 kWh 2288 kWh 683 kWh £586 £68 £655 £15,554 23.8 yrs £-2,460
4 kW 3962 kWh 3050 kWh 911 kWh £782 £91 £873 £17,588 20.1 yrs £-130
5 kW 4952 kWh 3813 kWh 1139 kWh £977 £114 £1,091 £19,623 18.0 yrs £2,201
6 kW 5942 kWh 4576 kWh 1367 kWh £1,173 £137 £1,309 £21,657 16.5 yrs £4,531
7 kW 6933 kWh 5338 kWh 1595 kWh £1,368 £159 £1,528 £23,692 15.5 yrs £6,861
8 kW 7923 kWh 6101 kWh 1822 kWh £1,564 £182 £1,746 £25,726 14.7 yrs £9,191

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 SW2

Figures below are tailored to SW2 — click through for full league tables.

Big-Roof Britain Rank #2138 of 2182
3.7 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #1297 of 2997
11.0 years (UK avg 11.3 years)
~£1,105 /yr • £12,207 upfront
Standing-Charge Drag Rank #347 of 2997
15.2% (UK avg 21.7%) drag on savings
£168 fixed • ~£1,105 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
990kWh/kW
A 1 kW system generates ~990 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: 18% • Flats: 73% • Bungalows: 0% Based on 18,126 properties

Coverage

Lambeth (100%)

Areas Covered

Brixton Acre Lane, Brixton Rush Common, Streatham Hill East, St Martin's, Clapham Park, Streatham Hill West & Thornton, Brixton Windrush, Herne Hill & Loughborough Junction + 3 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

SE24 (Lambeth)
≈1.4 km away
Local sunshine: ~993 kWh/kWp · +0% vs SW2
SW4 (Lambeth)
≈1.5 km away
Local sunshine: ~990 kWh/kWp · +0% vs SW2
SW9 (Lambeth)
≈1.7 km away
Local sunshine: ~991 kWh/kWp · +0% vs SW2
SW99 (Lambeth)
≈2.1 km away
Local sunshine: ~991 kWh/kWp · +0% vs SW2
SW12 (Wandsworth)
≈2.2 km away
Local sunshine: ~993 kWh/kWp · +0% vs SW2
SW8 (Lambeth)
≈2.5 km away
Local sunshine: ~991 kWh/kWp · +0% vs SW2

Similar sunshine across the UK

N13 (Enfield)
~990 kWh/kWp · +0% vs SW2
LE16 (Harborough)
~990 kWh/kWp · +0% vs SW2
LE94 (Harborough)
~990 kWh/kWp · +0% vs SW2