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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SW19 (Merton)

See if solar pays off for you in Merton — 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
£486
What you save every year
Profit Over 25 Years
£6,037
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 996 kWh/kW — 5 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 996 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)
996 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: £809, 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 1992 kWh 797 kWh 1195 kWh £204 £120 £324 £4,069 12.6 yrs £2,406
3 kW 2988 kWh 1195 kWh 1793 kWh £306 £179 £486 £6,104 12.6 yrs £3,609
4 kW 3984 kWh 1594 kWh 2390 kWh £408 £239 £647 £8,138 12.6 yrs £4,811
5 kW 4980 kWh 1992 kWh 2988 kWh £511 £299 £809 £10,173 12.6 yrs £6,014
6 kW 5976 kWh 2390 kWh 3586 kWh £613 £359 £971 £12,207 12.6 yrs £7,217
7 kW 6972 kWh 2789 kWh 4183 kWh £715 £418 £1,133 £14,242 12.6 yrs £8,420
8 kW 7968 kWh 3187 kWh 4781 kWh £817 £478 £1,295 £16,276 12.6 yrs £9,623

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: £965, 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 1992 kWh 1195 kWh 797 kWh £306 £80 £386 £6,169 16.0 yrs £1,551
3 kW 2988 kWh 1793 kWh 1195 kWh £459 £120 £579 £8,204 14.2 yrs £3,377
4 kW 3984 kWh 2390 kWh 1594 kWh £613 £159 £772 £10,238 13.3 yrs £5,202
5 kW 4980 kWh 2988 kWh 1992 kWh £766 £199 £965 £12,273 12.7 yrs £7,028
6 kW 5976 kWh 3586 kWh 2390 kWh £919 £239 £1,158 £14,307 12.4 yrs £8,853
7 kW 6972 kWh 4183 kWh 2789 kWh £1,072 £279 £1,351 £16,342 12.1 yrs £10,679
8 kW 7968 kWh 4781 kWh 3187 kWh £1,225 £319 £1,544 £18,376 11.9 yrs £12,504

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: £1,043, 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 1992 kWh 1394 kWh 598 kWh £357 £60 £417 £7,569 18.1 yrs £774
3 kW 2988 kWh 2092 kWh 896 kWh £536 £90 £626 £9,604 15.3 yrs £2,911
4 kW 3984 kWh 2789 kWh 1195 kWh £715 £120 £834 £11,638 13.9 yrs £5,048
5 kW 4980 kWh 3486 kWh 1494 kWh £893 £149 £1,043 £13,673 13.1 yrs £7,184
6 kW 5976 kWh 4183 kWh 1793 kWh £1,072 £179 £1,251 £15,707 12.6 yrs £9,321
7 kW 6972 kWh 4880 kWh 2092 kWh £1,251 £209 £1,460 £17,742 12.2 yrs £11,458
8 kW 7968 kWh 5578 kWh 2390 kWh £1,430 £239 £1,669 £19,776 11.9 yrs £13,595

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: £1,066, 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 1992 kWh 1454 kWh 538 kWh £373 £54 £426 £9,319 21.9 yrs £-789
3 kW 2988 kWh 2181 kWh 807 kWh £559 £81 £640 £11,354 17.7 yrs £1,441
4 kW 3984 kWh 2908 kWh 1076 kWh £745 £108 £853 £13,388 15.7 yrs £3,671
5 kW 4980 kWh 3635 kWh 1345 kWh £932 £134 £1,066 £15,423 14.5 yrs £5,901
6 kW 5976 kWh 4362 kWh 1614 kWh £1,118 £161 £1,279 £17,457 13.6 yrs £8,132
7 kW 6972 kWh 5090 kWh 1882 kWh £1,304 £188 £1,493 £19,492 13.1 yrs £10,362
8 kW 7968 kWh 5817 kWh 2151 kWh £1,491 £215 £1,706 £21,526 12.6 yrs £12,592

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: £1,082, 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 1992 kWh 1494 kWh 498 kWh £383 £50 £433 £11,069 25.6 yrs £-2,415
3 kW 2988 kWh 2241 kWh 747 kWh £574 £75 £649 £13,104 20.2 yrs £-122
4 kW 3984 kWh 2988 kWh 996 kWh £766 £100 £865 £15,138 17.5 yrs £2,170
5 kW 4980 kWh 3735 kWh 1245 kWh £957 £124 £1,082 £17,173 15.9 yrs £4,463
6 kW 5976 kWh 4482 kWh 1494 kWh £1,149 £149 £1,298 £19,207 14.8 yrs £6,755
7 kW 6972 kWh 5229 kWh 1743 kWh £1,340 £174 £1,514 £21,242 14.0 yrs £9,048
8 kW 7968 kWh 5976 kWh 1992 kWh £1,532 £199 £1,731 £23,276 13.4 yrs £11,341

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: £1,097, 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 1992 kWh 1534 kWh 458 kWh £393 £46 £439 £13,519 30.8 yrs £-4,740
3 kW 2988 kWh 2301 kWh 687 kWh £590 £69 £658 £15,554 23.6 yrs £-2,385
4 kW 3984 kWh 3068 kWh 916 kWh £786 £92 £878 £17,588 20.0 yrs £-31
5 kW 4980 kWh 3835 kWh 1145 kWh £983 £115 £1,097 £19,623 17.9 yrs £2,324
6 kW 5976 kWh 4601 kWh 1374 kWh £1,179 £137 £1,317 £21,657 16.4 yrs £4,679
7 kW 6972 kWh 5368 kWh 1604 kWh £1,376 £160 £1,536 £23,692 15.4 yrs £7,034
8 kW 7968 kWh 6135 kWh 1833 kWh £1,572 £183 £1,756 £25,726 14.7 yrs £9,389

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 SW19

Figures below are tailored to SW19 — click through for full league tables.

Big-Roof Britain Rank #2040 of 2182
4.0 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #1289 of 2997
11.0 years (UK avg 11.3 years)
~£1,111 /yr • £12,207 upfront
Standing-Charge Drag Rank #270 of 2997
15.1% (UK avg 21.7%) drag on savings
£168 fixed • ~£1,111 /yr value

Your Area at a Glance

Your Electricity Rate
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
996kWh/kW
A 1 kW system generates ~996 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: 34% • Flats: 60% • Bungalows: 0% Based on 23,934 properties

Coverage

Merton (90%)|Wandsworth (10%)

Areas Covered

Hillside, West Hill, Abbey, Village, Wimbledon Town & Dundonald, Wimbledon Park, Colliers Wood, Wandle + 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

SW20 (Merton)
≈0.8 km away
Local sunshine: ~996 kWh/kWp · +0% vs SW19
SM4 (Merton)
≈2.7 km away
Local sunshine: ~999 kWh/kWp · +0% vs SW19
SW17 (Wandsworth)
≈3.5 km away
Local sunshine: ~996 kWh/kWp · +0% vs SW19
KT3 (Kingston upon Thames)
≈3.6 km away
Local sunshine: ~996 kWh/kWp · +0% vs SW19
SW18 (Wandsworth)
≈3.7 km away
Local sunshine: ~992 kWh/kWp · -0% vs SW19
CR4 (Merton)
≈4.2 km away
Local sunshine: ~993 kWh/kWp · -0% vs SW19

Similar sunshine across the UK

TW5 (Hounslow)
~996 kWh/kWp · +0% vs SW19
KT13 (Elmbridge)
~996 kWh/kWp · +0% vs SW19
SG14 (East Hertfordshire)
~996 kWh/kWp · +0% vs SW19