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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SE12 (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
12.4 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£818
What you save every year
Profit Over 25 Years
£10,289
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 1007 kWh/kW — 17 above the regional median (991).

Read the full story

A typical roof here lands around 5.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 1007 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)
1007 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: £818, 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 2014 kWh 806 kWh 1209 kWh £207 £121 £327 £4,069 12.4 yrs £2,479
3 kW 3022 kWh 1209 kWh 1813 kWh £310 £181 £491 £6,104 12.4 yrs £3,718
4 kW 4029 kWh 1612 kWh 2417 kWh £413 £242 £655 £8,138 12.4 yrs £4,957
5 kW 5036 kWh 2014 kWh 3022 kWh £516 £302 £818 £10,173 12.4 yrs £6,196
6 kW 6043 kWh 2417 kWh 3626 kWh £620 £363 £982 £12,207 12.4 yrs £7,436
7 kW 7050 kWh 2820 kWh 4230 kWh £723 £423 £1,146 £14,242 12.4 yrs £8,675
8 kW 8058 kWh 3223 kWh 4835 kWh £826 £483 £1,310 £16,276 12.4 yrs £9,914

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: £976, Upfront: £12,273, 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 2014 kWh 1209 kWh 806 kWh £310 £81 £390 £6,169 15.8 yrs £1,638
3 kW 3022 kWh 1813 kWh 1209 kWh £465 £121 £586 £8,204 14.0 yrs £3,507
4 kW 4029 kWh 2417 kWh 1612 kWh £620 £161 £781 £10,238 13.1 yrs £5,376
5 kW 5036 kWh 3022 kWh 2014 kWh £774 £201 £976 £12,273 12.6 yrs £7,245
6 kW 6043 kWh 3626 kWh 2417 kWh £929 £242 £1,171 £14,307 12.2 yrs £9,114
7 kW 7050 kWh 4230 kWh 2820 kWh £1,084 £282 £1,366 £16,342 12.0 yrs £10,983
8 kW 8058 kWh 4835 kWh 3223 kWh £1,239 £322 £1,561 £18,376 11.8 yrs £12,852

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: £1,055, Upfront: £13,673, Break-even: 13.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2014 kWh 1410 kWh 604 kWh £361 £60 £422 £7,569 17.9 yrs £868
3 kW 3022 kWh 2115 kWh 906 kWh £542 £91 £633 £9,604 15.2 yrs £3,052
4 kW 4029 kWh 2820 kWh 1209 kWh £723 £121 £844 £11,638 13.8 yrs £5,235
5 kW 5036 kWh 3525 kWh 1511 kWh £904 £151 £1,055 £13,673 13.0 yrs £7,419
6 kW 6043 kWh 4230 kWh 1813 kWh £1,084 £181 £1,266 £15,707 12.4 yrs £9,603
7 kW 7050 kWh 4935 kWh 2115 kWh £1,265 £212 £1,476 £17,742 12.0 yrs £11,787
8 kW 8058 kWh 5640 kWh 2417 kWh £1,446 £242 £1,687 £19,776 11.7 yrs £13,971

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: £1,078, 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 2014 kWh 1471 kWh 544 kWh £377 £54 £431 £9,319 21.6 yrs £-693
3 kW 3022 kWh 2206 kWh 816 kWh £565 £82 £647 £11,354 17.6 yrs £1,585
4 kW 4029 kWh 2941 kWh 1088 kWh £754 £109 £863 £13,388 15.5 yrs £3,863
5 kW 5036 kWh 3676 kWh 1360 kWh £942 £136 £1,078 £15,423 14.3 yrs £6,142
6 kW 6043 kWh 4412 kWh 1632 kWh £1,131 £163 £1,294 £17,457 13.5 yrs £8,420
7 kW 7050 kWh 5147 kWh 1904 kWh £1,319 £190 £1,509 £19,492 12.9 yrs £10,698
8 kW 8058 kWh 5882 kWh 2176 kWh £1,508 £218 £1,725 £21,526 12.5 yrs £12,976

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: £1,094, Upfront: £17,173, Break-even: 15.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2014 kWh 1511 kWh 504 kWh £387 £50 £438 £11,069 25.3 yrs £-2,317
3 kW 3022 kWh 2266 kWh 755 kWh £581 £76 £656 £13,104 20.0 yrs £24
4 kW 4029 kWh 3022 kWh 1007 kWh £774 £101 £875 £15,138 17.3 yrs £2,365
5 kW 5036 kWh 3777 kWh 1259 kWh £968 £126 £1,094 £17,173 15.7 yrs £4,706
6 kW 6043 kWh 4532 kWh 1511 kWh £1,162 £151 £1,313 £19,207 14.6 yrs £7,048
7 kW 7050 kWh 5288 kWh 1763 kWh £1,355 £176 £1,532 £21,242 13.9 yrs £9,389
8 kW 8058 kWh 6043 kWh 2014 kWh £1,549 £201 £1,750 £23,276 13.3 yrs £11,730

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: £1,110, Upfront: £19,623, Break-even: 17.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2014 kWh 1551 kWh 463 kWh £398 £46 £444 £13,519 30.5 yrs £-4,642
3 kW 3022 kWh 2327 kWh 695 kWh £596 £69 £666 £15,554 23.4 yrs £-2,237
4 kW 4029 kWh 3102 kWh 927 kWh £795 £93 £888 £17,588 19.8 yrs £167
5 kW 5036 kWh 3878 kWh 1158 kWh £994 £116 £1,110 £19,623 17.7 yrs £2,571
6 kW 6043 kWh 4653 kWh 1390 kWh £1,193 £139 £1,332 £21,657 16.3 yrs £4,975
7 kW 7050 kWh 5429 kWh 1622 kWh £1,391 £162 £1,554 £23,692 15.2 yrs £7,380
8 kW 8058 kWh 6204 kWh 1853 kWh £1,590 £185 £1,776 £25,726 14.5 yrs £9,784

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 SE12

Figures below are tailored to SE12 — click through for full league tables.

Big-Roof Britain Rank #1863 of 2182
4.3 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #1178 of 2997
10.9 years (UK avg 11.3 years)
~£937 /yr • £10,173 upfront
Standing-Charge Drag Rank #954 of 2997
17.9% (UK avg 21.7%) drag on savings
£168 fixed • ~£937 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
1007kWh/kW
A 1 kW system generates ~1007 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
5.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 48% • Flats: 43% • Bungalows: 1% Based on 7,048 properties

Coverage

Lewisham (60%)|Greenwich (39%)

Areas Covered

Grove Park, Lee Green, Eltham Town & Avery Hill, Middle Park & Horn Park, Kidbrooke Village & Sutcliffe, Blackheath, Hither Green, Mottingham

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

SE3 (Greenwich)
≈1.9 km away
Local sunshine: ~1,005 kWh/kWp · -0% vs SE12
SE9 (Greenwich)
≈2.1 km away
Local sunshine: ~1,012 kWh/kWp · +1% vs SE12
SE13 (Lewisham)
≈2.7 km away
Local sunshine: ~993 kWh/kWp · -1% vs SE12
SE6 (Lewisham)
≈3.2 km away
Local sunshine: ~1,000 kWh/kWp · -1% vs SE12
SE7 (Greenwich)
≈4.0 km away
Local sunshine: ~1,006 kWh/kWp · -0% vs SE12
SE10 (Greenwich)
≈4.1 km away
Local sunshine: ~1,006 kWh/kWp · -0% vs SE12

Similar sunshine across the UK

RH19 (Mid Sussex)
~1,007 kWh/kWp · +0% vs SE12
DN33 (North East Lincolnshire)
~1,007 kWh/kWp · +0% vs SE12
PE5 (Peterborough)
~1,007 kWh/kWp · -0% vs SE12