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Solar panel cost in Merton (SM4)

See realistic solar installation costs, savings and payback for SM4 (Merton) in under a minute using official UK data. Start with the calculator, then get a no-obligation quote from an MCS-certified installer. You can also ask the SolarByPostcode assistant to sanity-check your roof, bills and plans.

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
11.1 years
After this, it's pure profit
Upfront Cost
£7,307
What you pay to get started
Annual Benefit
£661
What you save every year
Profit Over 25 Years
£9,209
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: The official cost per kW is lower above 4 kW, so a 5–6 kW system can pay back a little faster than a 3–4 kW system on otherwise identical assumptions.
  • 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

Panel costs: Uses March 2026 TIC mean installation costs: £1,827/kW up to 4 kW and £1,628/kW above 4 kW.

Other costs: Battery prices are modelled at £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 26.35p/kWh with a 44.78p/day standing charge. Your postcode’s south-facing sunshine yield is 999 kWh/kW — 8 above the regional median (991).

Read the full story

A typical roof here lands around 4.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 999 kWh per year on a south-facing roof. We value self-used electricity at 26.4p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.4p/kWh
Standing charge
44.8p/day
Sunshine yield (south)
999 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: £826, Upfront: £9,134, Break-even: 11.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1997 kWh 799 kWh 1198 kWh £210 £120 £330 £3,654 11.1 yrs £2,953
3 kW 2996 kWh 1198 kWh 1797 kWh £316 £180 £495 £5,481 11.1 yrs £4,429
4 kW 3994 kWh 1598 kWh 2397 kWh £421 £240 £661 £7,307 11.1 yrs £5,906
5 kW 4993 kWh 1997 kWh 2996 kWh £526 £300 £826 £9,134 11.1 yrs £7,382
6 kW 5991 kWh 2397 kWh 3595 kWh £631 £359 £991 £10,961 11.1 yrs £8,859
7 kW 6990 kWh 2796 kWh 4194 kWh £737 £419 £1,156 £12,788 11.1 yrs £10,335
8 kW 7989 kWh 3195 kWh 4793 kWh £842 £479 £1,321 £14,615 11.1 yrs £11,811

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,827, battery £/kWh = 700.

3 kWh battery 5 kW example → Annual benefit: £989, Upfront: £11,234, Break-even: 11.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1997 kWh 1198 kWh 799 kWh £316 £80 £396 £5,754 14.5 yrs £2,159
3 kW 2996 kWh 1797 kWh 1198 kWh £474 £120 £593 £7,581 12.8 yrs £4,288
4 kW 3994 kWh 2397 kWh 1598 kWh £631 £160 £791 £9,407 11.9 yrs £6,418
5 kW 4993 kWh 2996 kWh 1997 kWh £789 £200 £989 £11,234 11.4 yrs £8,547
6 kW 5991 kWh 3595 kWh 2397 kWh £947 £240 £1,187 £13,061 11.0 yrs £10,677
7 kW 6990 kWh 4194 kWh 2796 kWh £1,105 £280 £1,385 £14,888 10.8 yrs £12,806
8 kW 7989 kWh 4793 kWh 3195 kWh £1,263 £320 £1,583 £16,715 10.6 yrs £14,936

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,827, battery £/kWh = 700.

5 kWh battery 5 kW example → Annual benefit: £1,071, Upfront: £12,634, Break-even: 11.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1997 kWh 1398 kWh 599 kWh £368 £60 £428 £7,154 16.7 yrs £1,412
3 kW 2996 kWh 2097 kWh 899 kWh £553 £90 £642 £8,981 14.0 yrs £3,868
4 kW 3994 kWh 2796 kWh 1198 kWh £737 £120 £857 £10,807 12.6 yrs £6,324
5 kW 4993 kWh 3495 kWh 1498 kWh £921 £150 £1,071 £12,634 11.8 yrs £8,780
6 kW 5991 kWh 4194 kWh 1797 kWh £1,105 £180 £1,285 £14,461 11.3 yrs £11,236
7 kW 6990 kWh 4893 kWh 2097 kWh £1,289 £210 £1,499 £16,288 10.9 yrs £13,692
8 kW 7989 kWh 5592 kWh 2397 kWh £1,473 £240 £1,713 £18,115 10.6 yrs £16,148

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,827, battery £/kWh = 700.

7.5 kWh battery 5 kW example → Annual benefit: £1,095, Upfront: £14,384, 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 1997 kWh 1458 kWh 539 kWh £384 £54 £438 £8,904 20.3 yrs £-142
3 kW 2996 kWh 2187 kWh 809 kWh £576 £81 £657 £10,731 16.3 yrs £2,412
4 kW 3994 kWh 2916 kWh 1078 kWh £768 £108 £876 £12,557 14.3 yrs £4,966
5 kW 4993 kWh 3645 kWh 1348 kWh £960 £135 £1,095 £14,384 13.1 yrs £7,520
6 kW 5991 kWh 4374 kWh 1618 kWh £1,152 £162 £1,314 £16,211 12.3 yrs £10,074
7 kW 6990 kWh 5103 kWh 1887 kWh £1,345 £189 £1,533 £18,038 11.8 yrs £12,628
8 kW 7989 kWh 5832 kWh 2157 kWh £1,537 £216 £1,752 £19,865 11.3 yrs £15,182

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,827, battery £/kWh = 700.

10 kWh battery 5 kW example → Annual benefit: £1,112, Upfront: £16,134, 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 1997 kWh 1498 kWh 499 kWh £395 £50 £445 £10,654 24.0 yrs £-1,761
3 kW 2996 kWh 2247 kWh 749 kWh £592 £75 £667 £12,481 18.7 yrs £858
4 kW 3994 kWh 2996 kWh 999 kWh £789 £100 £889 £14,307 16.1 yrs £3,477
5 kW 4993 kWh 3745 kWh 1248 kWh £987 £125 £1,112 £16,134 14.5 yrs £6,096
6 kW 5991 kWh 4494 kWh 1498 kWh £1,184 £150 £1,334 £17,961 13.5 yrs £8,716
7 kW 6990 kWh 5242 kWh 1747 kWh £1,381 £175 £1,556 £19,788 12.7 yrs £11,335
8 kW 7989 kWh 5991 kWh 1997 kWh £1,579 £200 £1,778 £21,615 12.2 yrs £13,954

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,827, battery £/kWh = 700.

13.5 kWh battery 5 kW example → Annual benefit: £1,128, Upfront: £18,584, Break-even: 16.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1997 kWh 1538 kWh 459 kWh £405 £46 £451 £13,104 29.0 yrs £-4,081
3 kW 2996 kWh 2307 kWh 689 kWh £608 £69 £677 £14,931 22.1 yrs £-1,396
4 kW 3994 kWh 3076 kWh 919 kWh £810 £92 £902 £16,757 18.6 yrs £1,288
5 kW 4993 kWh 3844 kWh 1148 kWh £1,013 £115 £1,128 £18,584 16.5 yrs £3,973
6 kW 5991 kWh 4613 kWh 1378 kWh £1,216 £138 £1,353 £20,411 15.1 yrs £6,658
7 kW 6990 kWh 5382 kWh 1608 kWh £1,418 £161 £1,579 £22,238 14.1 yrs £9,342
8 kW 7989 kWh 6151 kWh 1837 kWh £1,621 £184 £1,805 £24,065 13.3 yrs £12,027

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,827, 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.

Before you request quotes in Merton

Use the numbers above to sanity-check installer quotes. The main things to compare are system size, battery assumptions, payback claims, MCS certification, DNO paperwork and export assumptions.

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Check what MCS certification means

Understand DNO, G98 and G99 export limits

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Insights for SM4

Figures below are tailored to SM4 — click through for full league tables.

Big-Roof Britain Rank #1961 of 2182
4.2 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #2116 of 2996
11.1 years (UK avg 10.8 years)
~£661 /yr • £7,307 upfront
Standing-Charge Drag Rank #1368 of 2996
24.7% (UK avg 26.6%) drag on savings
£163 fixed • ~£661 /yr value
Aspect Penalty View ranking →
East −21.3% West −19.5%
Typical output loss versus a south-facing roof (lower is better)

Seasonal solar output in SM4

Monthly generation per kilowatt of solar panels

kWh 39 Jan 51 Feb 84 Mar 112 Apr 119 May 121 Jun 122 Jul 109 Aug 93 Sep 68 Oct 46 Nov 35 Dec
Best month Worst month Winter (Dec–Feb) Other months

Winter output: 49.8% of an average month (Dec–Feb)

Best / worst month: Jul / Dec

These figures show output per kilowatt (kW) of panels installed. In winter, a 1 kW system here produces about 41 kWh per month; the average month produces around 83 kWh. So a typical 4 kW home system would generate roughly 166 kWh in winter, or 333 kWh in an average month.

Your Area at a Glance

Your Electricity Rate
26.35p/kWh
Daily Fixed Charge
44.78p/day
Local Sunshine
999kWh/kW
A 1 kW system generates ~999 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
4.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 66% • Flats: 27% • Bungalows: 1% Based on 7,739 properties

Coverage

Merton (93%)|Sutton (7%)

Areas Covered

St Helier, Lower Morden, Ravensbury, Merton Park, Cannon Hill, St Helier West, Belmont, St Helier East + 2 more

Data Sources & Assumptions

Solar yield: PVGIS (EU Joint Research Centre), January 2025 data

Electricity rates: Ofgem price cap, Q3 2026

Installation costs: DESNZ/MCS data, March 2026 (TIC)

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)
≈2.6 km away
Local sunshine: ~996 kWh/kWp · -0% vs SM4
SW19 (Merton)
≈2.7 km away
Local sunshine: ~996 kWh/kWp · -0% vs SM4
CR4 (Merton)
≈3.2 km away
Local sunshine: ~993 kWh/kWp · -1% vs SM4
KT3 (Kingston upon Thames)
≈3.9 km away
Local sunshine: ~996 kWh/kWp · -0% vs SM4
SW17 (Wandsworth)
≈4.4 km away
Local sunshine: ~996 kWh/kWp · -0% vs SM4
SW18 (Wandsworth)
≈5.9 km away
Local sunshine: ~992 kWh/kWp · -1% vs SM4

Similar sunshine across the UK

GU3 (Guildford)
~999 kWh/kWp · +0% vs SM4
TW20 (Runnymede)
~999 kWh/kWp · +0% vs SM4
PE33 (King's Lynn and West Norfolk)
~999 kWh/kWp · -0% vs SM4