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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SE9 (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
£10,173
What you pay to get started
Annual Benefit
£823
What you save every year
Profit Over 25 Years
£10,395
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 1012 kWh/kW — 22 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 1012 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)
1012 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: £823, 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 2025 kWh 810 kWh 1215 kWh £208 £121 £329 £4,069 12.4 yrs £2,513
3 kW 3037 kWh 1215 kWh 1822 kWh £311 £182 £494 £6,104 12.4 yrs £3,769
4 kW 4050 kWh 1620 kWh 2430 kWh £415 £243 £658 £8,138 12.4 yrs £5,025
5 kW 5062 kWh 2025 kWh 3037 kWh £519 £304 £823 £10,173 12.4 yrs £6,282
6 kW 6075 kWh 2430 kWh 3645 kWh £623 £364 £987 £12,207 12.4 yrs £7,538
7 kW 7087 kWh 2835 kWh 4252 kWh £727 £425 £1,152 £14,242 12.4 yrs £8,795
8 kW 8100 kWh 3240 kWh 4860 kWh £830 £486 £1,316 £16,276 12.4 yrs £10,051

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: £981, 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 2025 kWh 1215 kWh 810 kWh £311 £81 £392 £6,169 15.7 yrs £1,679
3 kW 3037 kWh 1822 kWh 1215 kWh £467 £121 £589 £8,204 13.9 yrs £3,568
4 kW 4050 kWh 2430 kWh 1620 kWh £623 £162 £785 £10,238 13.0 yrs £5,457
5 kW 5062 kWh 3037 kWh 2025 kWh £778 £202 £981 £12,273 12.5 yrs £7,347
6 kW 6075 kWh 3645 kWh 2430 kWh £934 £243 £1,177 £14,307 12.2 yrs £9,236
7 kW 7087 kWh 4252 kWh 2835 kWh £1,090 £283 £1,373 £16,342 11.9 yrs £11,125
8 kW 8100 kWh 4860 kWh 3240 kWh £1,246 £324 £1,570 £18,376 11.7 yrs £13,015

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: £1,060, 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 2025 kWh 1417 kWh 607 kWh £363 £61 £424 £7,569 17.9 yrs £912
3 kW 3037 kWh 2126 kWh 911 kWh £545 £91 £636 £9,604 15.1 yrs £3,117
4 kW 4050 kWh 2835 kWh 1215 kWh £727 £121 £848 £11,638 13.7 yrs £5,323
5 kW 5062 kWh 3544 kWh 1519 kWh £908 £152 £1,060 £13,673 12.9 yrs £7,529
6 kW 6075 kWh 4252 kWh 1822 kWh £1,090 £182 £1,272 £15,707 12.3 yrs £9,735
7 kW 7087 kWh 4961 kWh 2126 kWh £1,272 £213 £1,484 £17,742 12.0 yrs £11,941
8 kW 8100 kWh 5670 kWh 2430 kWh £1,453 £243 £1,696 £19,776 11.7 yrs £14,147

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: £1,084, Upfront: £15,423, Break-even: 14.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2025 kWh 1478 kWh 547 kWh £379 £55 £434 £9,319 21.5 yrs £-648
3 kW 3037 kWh 2217 kWh 820 kWh £568 £82 £650 £11,354 17.5 yrs £1,652
4 kW 4050 kWh 2956 kWh 1093 kWh £758 £109 £867 £13,388 15.4 yrs £3,953
5 kW 5062 kWh 3695 kWh 1367 kWh £947 £137 £1,084 £15,423 14.2 yrs £6,254
6 kW 6075 kWh 4435 kWh 1640 kWh £1,137 £164 £1,301 £17,457 13.4 yrs £8,555
7 kW 7087 kWh 5174 kWh 1914 kWh £1,326 £191 £1,517 £19,492 12.8 yrs £10,855
8 kW 8100 kWh 5913 kWh 2187 kWh £1,515 £219 £1,734 £21,526 12.4 yrs £13,156

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: £1,100, 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 2025 kWh 1519 kWh 506 kWh £389 £51 £440 £11,069 25.2 yrs £-2,272
3 kW 3037 kWh 2278 kWh 759 kWh £584 £76 £660 £13,104 19.9 yrs £92
4 kW 4050 kWh 3037 kWh 1012 kWh £778 £101 £880 £15,138 17.2 yrs £2,456
5 kW 5062 kWh 3797 kWh 1266 kWh £973 £127 £1,100 £17,173 15.6 yrs £4,820
6 kW 6075 kWh 4556 kWh 1519 kWh £1,168 £152 £1,320 £19,207 14.6 yrs £7,184
7 kW 7087 kWh 5315 kWh 1772 kWh £1,362 £177 £1,540 £21,242 13.8 yrs £9,549
8 kW 8100 kWh 6075 kWh 2025 kWh £1,557 £202 £1,759 £23,276 13.2 yrs £11,913

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: £1,115, 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 2025 kWh 1559 kWh 466 kWh £400 £47 £446 £13,519 30.3 yrs £-4,595
3 kW 3037 kWh 2339 kWh 699 kWh £599 £70 £669 £15,554 23.2 yrs £-2,168
4 kW 4050 kWh 3118 kWh 931 kWh £799 £93 £892 £17,588 19.7 yrs £260
5 kW 5062 kWh 3898 kWh 1164 kWh £999 £116 £1,115 £19,623 17.6 yrs £2,687
6 kW 6075 kWh 4678 kWh 1397 kWh £1,199 £140 £1,339 £21,657 16.2 yrs £5,114
7 kW 7087 kWh 5457 kWh 1630 kWh £1,399 £163 £1,562 £23,692 15.2 yrs £7,542
8 kW 8100 kWh 6237 kWh 1863 kWh £1,598 £186 £1,785 £25,726 14.4 yrs £9,969

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 SE9

Figures below are tailored to SE9 — click through for full league tables.

Big-Roof Britain Rank #1686 of 2182
4.5 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #1063 of 2997
10.8 years (UK avg 11.3 years)
~£941 /yr • £10,173 upfront
Standing-Charge Drag Rank #971 of 2997
17.9% (UK avg 21.7%) drag on savings
£168 fixed • ~£941 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
1012kWh/kW
A 1 kW system generates ~1012 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: 60% • Flats: 33% • Bungalows: 2% Based on 13,636 properties

Coverage

Greenwich (85%)|Bromley (10%)|Lewisham (2%)|Bexley (2%)

Areas Covered

Eltham Town & Avery Hill, Mottingham, Coldharbour & New Eltham, Eltham Park & Progress, Mottingham, Eltham Page, Middle Park & Horn Park, Grove Park + 5 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

SE12 (Lewisham)
≈2.1 km away
Local sunshine: ~1,007 kWh/kWp · -1% vs SE9
SE3 (Greenwich)
≈3.2 km away
Local sunshine: ~1,005 kWh/kWp · -1% vs SE9
DA15 (Bexley)
≈3.7 km away
Local sunshine: ~1,018 kWh/kWp · +1% vs SE9
DA16 (Bexley)
≈4.1 km away
Local sunshine: ~1,016 kWh/kWp · +0% vs SE9
SE7 (Greenwich)
≈4.2 km away
Local sunshine: ~1,006 kWh/kWp · -1% vs SE9
BR7 (Bromley)
≈4.3 km away
Local sunshine: ~1,012 kWh/kWp · -0% vs SE9

Similar sunshine across the UK

CM15 (Brentwood)
~1,012 kWh/kWp · -0% vs SE9
CM17 (Harlow)
~1,012 kWh/kWp · -0% vs SE9
PE29 (Huntingdonshire)
~1,012 kWh/kWp · +0% vs SE9