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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SE4 (Lewisham)

See if solar pays off for you in Lewisham — 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
£484
What you save every year
Profit Over 25 Years
£6,009
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 994 kWh/kW — 3 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 994 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)
994 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: £807, 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 1987 kWh 795 kWh 1192 kWh £204 £119 £323 £4,069 12.6 yrs £2,391
3 kW 2981 kWh 1192 kWh 1789 kWh £306 £179 £484 £6,104 12.6 yrs £3,586
4 kW 3975 kWh 1590 kWh 2385 kWh £408 £238 £646 £8,138 12.6 yrs £4,782
5 kW 4969 kWh 1987 kWh 2981 kWh £509 £298 £807 £10,173 12.6 yrs £5,977
6 kW 5962 kWh 2385 kWh 3577 kWh £611 £358 £969 £12,207 12.6 yrs £7,173
7 kW 6956 kWh 2782 kWh 4174 kWh £713 £417 £1,130 £14,242 12.6 yrs £8,368
8 kW 7950 kWh 3180 kWh 4770 kWh £815 £477 £1,292 £16,276 12.6 yrs £9,564

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: £963, Upfront: £12,273, 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 1987 kWh 1192 kWh 795 kWh £306 £79 £385 £6,169 16.0 yrs £1,533
3 kW 2981 kWh 1789 kWh 1192 kWh £458 £119 £578 £8,204 14.2 yrs £3,350
4 kW 3975 kWh 2385 kWh 1590 kWh £611 £159 £770 £10,238 13.3 yrs £5,167
5 kW 4969 kWh 2981 kWh 1987 kWh £764 £199 £963 £12,273 12.7 yrs £6,984
6 kW 5962 kWh 3577 kWh 2385 kWh £917 £238 £1,155 £14,307 12.4 yrs £8,800
7 kW 6956 kWh 4174 kWh 2782 kWh £1,070 £278 £1,348 £16,342 12.1 yrs £10,617
8 kW 7950 kWh 4770 kWh 3180 kWh £1,223 £318 £1,540 £18,376 11.9 yrs £12,434

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: £1,040, Upfront: £13,673, Break-even: 13.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1987 kWh 1391 kWh 596 kWh £357 £60 £416 £7,569 18.2 yrs £755
3 kW 2981 kWh 2087 kWh 894 kWh £535 £89 £624 £9,604 15.4 yrs £2,882
4 kW 3975 kWh 2782 kWh 1192 kWh £713 £119 £832 £11,638 14.0 yrs £5,009
5 kW 4969 kWh 3478 kWh 1491 kWh £891 £149 £1,040 £13,673 13.1 yrs £7,137
6 kW 5962 kWh 4174 kWh 1789 kWh £1,070 £179 £1,249 £15,707 12.6 yrs £9,264
7 kW 6956 kWh 4869 kWh 2087 kWh £1,248 £209 £1,457 £17,742 12.2 yrs £11,391
8 kW 7950 kWh 5565 kWh 2385 kWh £1,426 £238 £1,665 £19,776 11.9 yrs £13,519

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: £1,064, 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 1987 kWh 1451 kWh 537 kWh £372 £54 £426 £9,319 21.9 yrs £-809
3 kW 2981 kWh 2176 kWh 805 kWh £558 £80 £638 £11,354 17.8 yrs £1,412
4 kW 3975 kWh 2902 kWh 1073 kWh £744 £107 £851 £13,388 15.7 yrs £3,632
5 kW 4969 kWh 3627 kWh 1342 kWh £930 £134 £1,064 £15,423 14.5 yrs £5,853
6 kW 5962 kWh 4352 kWh 1610 kWh £1,116 £161 £1,277 £17,457 13.7 yrs £8,073
7 kW 6956 kWh 5078 kWh 1878 kWh £1,301 £188 £1,489 £19,492 13.1 yrs £10,294
8 kW 7950 kWh 5803 kWh 2146 kWh £1,487 £215 £1,702 £21,526 12.6 yrs £12,514

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: £1,079, Upfront: £17,173, Break-even: 15.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1987 kWh 1491 kWh 497 kWh £382 £50 £432 £11,069 25.6 yrs £-2,435
3 kW 2981 kWh 2236 kWh 745 kWh £573 £75 £648 £13,104 20.2 yrs £-152
4 kW 3975 kWh 2981 kWh 994 kWh £764 £99 £863 £15,138 17.5 yrs £2,131
5 kW 4969 kWh 3726 kWh 1242 kWh £955 £124 £1,079 £17,173 15.9 yrs £4,413
6 kW 5962 kWh 4472 kWh 1491 kWh £1,146 £149 £1,295 £19,207 14.8 yrs £6,696
7 kW 6956 kWh 5217 kWh 1739 kWh £1,337 £174 £1,511 £21,242 14.1 yrs £8,979
8 kW 7950 kWh 5962 kWh 1987 kWh £1,528 £199 £1,727 £23,276 13.5 yrs £11,261

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: £1,095, Upfront: £19,623, Break-even: 17.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1987 kWh 1530 kWh 457 kWh £392 £46 £438 £13,519 30.9 yrs £-4,760
3 kW 2981 kWh 2295 kWh 686 kWh £588 £69 £657 £15,554 23.7 yrs £-2,416
4 kW 3975 kWh 3061 kWh 914 kWh £784 £91 £876 £17,588 20.1 yrs £-71
5 kW 4969 kWh 3826 kWh 1143 kWh £981 £114 £1,095 £19,623 17.9 yrs £2,274
6 kW 5962 kWh 4591 kWh 1371 kWh £1,177 £137 £1,314 £21,657 16.5 yrs £4,619
7 kW 6956 kWh 5356 kWh 1600 kWh £1,373 £160 £1,533 £23,692 15.5 yrs £6,964
8 kW 7950 kWh 6121 kWh 1828 kWh £1,569 £183 £1,752 £25,726 14.7 yrs £9,308

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 SE4

Figures below are tailored to SE4 — click through for full league tables.

Big-Roof Britain Rank #2078 of 2182
4.0 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #1275 of 2997
11.0 years (UK avg 11.3 years)
~£1,109 /yr • £12,207 upfront
Standing-Charge Drag Rank #311 of 2997
15.2% (UK avg 21.7%) drag on savings
£168 fixed • ~£1,109 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
994kWh/kW
A 1 kW system generates ~994 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: 33% • Flats: 61% • Bungalows: 0% Based on 8,273 properties

Coverage

Lewisham (99%)|Southwark (1%)

Areas Covered

Brockley, Telegraph Hill, Crofton Park, Ladywell, Nunhead & Queen's Road, Peckham Rye

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

SE14 (Lewisham)
≈1.4 km away
Local sunshine: ~994 kWh/kWp · +0% vs SE4
SE13 (Lewisham)
≈1.6 km away
Local sunshine: ~993 kWh/kWp · -0% vs SE4
SE8 (Lewisham)
≈2.1 km away
Local sunshine: ~994 kWh/kWp · +0% vs SE4
SE15 (Southwark)
≈2.6 km away
Local sunshine: ~993 kWh/kWp · -0% vs SE4
SE22 (Southwark)
≈2.8 km away
Local sunshine: ~997 kWh/kWp · +0% vs SE4
SE6 (Lewisham)
≈3.0 km away
Local sunshine: ~1,000 kWh/kWp · +1% vs SE4

Similar sunshine across the UK

OX29 (West Oxfordshire)
~994 kWh/kWp · +0% vs SE4
GU2 (Guildford)
~994 kWh/kWp · -0% vs SE4
SL2 (Slough)
~994 kWh/kWp · -0% vs SE4