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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SE23 (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
12.5 years
After this, it's pure profit
Upfront Cost
£6,104
What you pay to get started
Annual Benefit
£487
What you save every year
Profit Over 25 Years
£6,082
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 1000 kWh/kW — 9 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 1000 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)
1000 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: £812, Upfront: £10,173, 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 1999 kWh 800 kWh 1200 kWh £205 £120 £325 £4,069 12.5 yrs £2,430
3 kW 2999 kWh 1200 kWh 1799 kWh £307 £180 £487 £6,104 12.5 yrs £3,645
4 kW 3999 kWh 1599 kWh 2399 kWh £410 £240 £650 £8,138 12.5 yrs £4,859
5 kW 4998 kWh 1999 kWh 2999 kWh £512 £300 £812 £10,173 12.5 yrs £6,074
6 kW 5998 kWh 2399 kWh 3599 kWh £615 £360 £975 £12,207 12.5 yrs £7,289
7 kW 6998 kWh 2799 kWh 4199 kWh £717 £420 £1,137 £14,242 12.5 yrs £8,504
8 kW 7997 kWh 3199 kWh 4798 kWh £820 £480 £1,300 £16,276 12.5 yrs £9,719

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: £969, 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 1999 kWh 1200 kWh 800 kWh £307 £80 £387 £6,169 15.9 yrs £1,580
3 kW 2999 kWh 1799 kWh 1200 kWh £461 £120 £581 £8,204 14.1 yrs £3,420
4 kW 3999 kWh 2399 kWh 1599 kWh £615 £160 £775 £10,238 13.2 yrs £5,259
5 kW 4998 kWh 2999 kWh 1999 kWh £769 £200 £969 £12,273 12.7 yrs £7,099
6 kW 5998 kWh 3599 kWh 2399 kWh £922 £240 £1,162 £14,307 12.3 yrs £8,939
7 kW 6998 kWh 4199 kWh 2799 kWh £1,076 £280 £1,356 £16,342 12.1 yrs £10,779
8 kW 7997 kWh 4798 kWh 3199 kWh £1,230 £320 £1,550 £18,376 11.9 yrs £12,619

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: £1,047, 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 1999 kWh 1400 kWh 600 kWh £359 £60 £419 £7,569 18.1 yrs £805
3 kW 2999 kWh 2099 kWh 900 kWh £538 £90 £628 £9,604 15.3 yrs £2,957
4 kW 3999 kWh 2799 kWh 1200 kWh £717 £120 £837 £11,638 13.9 yrs £5,109
5 kW 4998 kWh 3499 kWh 1500 kWh £897 £150 £1,047 £13,673 13.1 yrs £7,262
6 kW 5998 kWh 4199 kWh 1799 kWh £1,076 £180 £1,256 £15,707 12.5 yrs £9,414
7 kW 6998 kWh 4898 kWh 2099 kWh £1,255 £210 £1,465 £17,742 12.1 yrs £11,566
8 kW 7997 kWh 5598 kWh 2399 kWh £1,435 £240 £1,675 £19,776 11.8 yrs £13,719

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: £1,070, Upfront: £15,423, Break-even: 14.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1999 kWh 1460 kWh 540 kWh £374 £54 £428 £9,319 21.8 yrs £-758
3 kW 2999 kWh 2189 kWh 810 kWh £561 £81 £642 £11,354 17.7 yrs £1,488
4 kW 3999 kWh 2919 kWh 1080 kWh £748 £108 £856 £13,388 15.6 yrs £3,734
5 kW 4998 kWh 3649 kWh 1350 kWh £935 £135 £1,070 £15,423 14.4 yrs £5,980
6 kW 5998 kWh 4379 kWh 1619 kWh £1,122 £162 £1,284 £17,457 13.6 yrs £8,227
7 kW 6998 kWh 5108 kWh 1889 kWh £1,309 £189 £1,498 £19,492 13.0 yrs £10,473
8 kW 7997 kWh 5838 kWh 2159 kWh £1,496 £216 £1,712 £21,526 12.6 yrs £12,719

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: £1,086, Upfront: £17,173, Break-even: 15.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1999 kWh 1500 kWh 500 kWh £384 £50 £434 £11,069 25.5 yrs £-2,383
3 kW 2999 kWh 2249 kWh 750 kWh £576 £75 £651 £13,104 20.1 yrs £-74
4 kW 3999 kWh 2999 kWh 1000 kWh £769 £100 £869 £15,138 17.4 yrs £2,234
5 kW 4998 kWh 3749 kWh 1250 kWh £961 £125 £1,086 £17,173 15.8 yrs £4,543
6 kW 5998 kWh 4499 kWh 1500 kWh £1,153 £150 £1,303 £19,207 14.7 yrs £6,852
7 kW 6998 kWh 5248 kWh 1749 kWh £1,345 £175 £1,520 £21,242 14.0 yrs £9,160
8 kW 7997 kWh 5998 kWh 1999 kWh £1,537 £200 £1,737 £23,276 13.4 yrs £11,469

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: £1,101, Upfront: £19,623, Break-even: 17.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1999 kWh 1540 kWh 460 kWh £395 £46 £441 £13,519 30.7 yrs £-4,708
3 kW 2999 kWh 2309 kWh 690 kWh £592 £69 £661 £15,554 23.5 yrs £-2,337
4 kW 3999 kWh 3079 kWh 920 kWh £789 £92 £881 £17,588 20.0 yrs £34
5 kW 4998 kWh 3849 kWh 1150 kWh £986 £115 £1,101 £19,623 17.8 yrs £2,405
6 kW 5998 kWh 4619 kWh 1380 kWh £1,184 £138 £1,322 £21,657 16.4 yrs £4,777
7 kW 6998 kWh 5388 kWh 1609 kWh £1,381 £161 £1,542 £23,692 15.4 yrs £7,148
8 kW 7997 kWh 6158 kWh 1839 kWh £1,578 £184 £1,762 £25,726 14.6 yrs £9,519

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 SE23

Figures below are tailored to SE23 — click through for full league tables.

Big-Roof Britain Rank #2126 of 2182
3.8 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #1179 of 2997
10.9 years (UK avg 11.3 years)
~£1,115 /yr • £12,207 upfront
Standing-Charge Drag Rank #275 of 2997
15.1% (UK avg 21.7%) drag on savings
£168 fixed • ~£1,115 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
1000kWh/kW
A 1 kW system generates ~1000 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: 27% • Flats: 66% • Bungalows: 0% Based on 10,679 properties

Coverage

Lewisham (97%)|Southwark (3%)

Areas Covered

Perry Vale, Forest Hill, Crofton Park, Peckham Rye, Dulwich Wood, Dulwich Hill

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

SE26 (Lewisham)
≈1.2 km away
Local sunshine: ~1,000 kWh/kWp · -0% vs SE23
SE22 (Southwark)
≈2.3 km away
Local sunshine: ~997 kWh/kWp · -0% vs SE23
SE6 (Lewisham)
≈2.3 km away
Local sunshine: ~1,000 kWh/kWp · -0% vs SE23
SE21 (Southwark)
≈2.4 km away
Local sunshine: ~996 kWh/kWp · -0% vs SE23
SE20 (Bromley)
≈2.6 km away
Local sunshine: ~997 kWh/kWp · -0% vs SE23
SE4 (Lewisham)
≈3.1 km away
Local sunshine: ~994 kWh/kWp · -1% vs SE23

Similar sunshine across the UK

UB8 (Hillingdon)
~1,000 kWh/kWp · -0% vs SE23
GU12 (Guildford)
~1,000 kWh/kWp · -0% vs SE23
UB10 (Hillingdon)
~1,000 kWh/kWp · -0% vs SE23