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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TW3 (Hounslow)

See if solar pays off for you in Hounslow — 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
12.3 years
After this, it's pure profit
Upfront Cost
£6,104
What you pay to get started
Annual Benefit
£496
What you save every year
Profit Over 25 Years
£6,289
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 Southern, the current unit rate is 26.48p/kWh with a 44.62p/day standing charge. Your postcode’s south-facing sunshine yield is 996 kWh/kW — 5 below the regional median (1001).

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 26.5p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.5p/kWh
Standing charge
44.6p/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: £826, Upfront: £10,173, Break-even: 12.3 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 £211 £120 £330 £4,069 12.3 yrs £2,541
3 kW 2988 kWh 1195 kWh 1793 kWh £316 £179 £496 £6,104 12.3 yrs £3,811
4 kW 3984 kWh 1593 kWh 2390 kWh £422 £239 £661 £8,138 12.3 yrs £5,081
5 kW 4979 kWh 1992 kWh 2988 kWh £527 £299 £826 £10,173 12.3 yrs £6,351
6 kW 5975 kWh 2390 kWh 3585 kWh £633 £359 £991 £12,207 12.3 yrs £7,622
7 kW 6971 kWh 2788 kWh 4183 kWh £738 £418 £1,157 £14,242 12.3 yrs £8,892
8 kW 7967 kWh 3187 kWh 4780 kWh £844 £478 £1,322 £16,276 12.3 yrs £10,162

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: £990, Upfront: £12,273, 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 1992 kWh 1195 kWh 797 kWh £316 £80 £396 £6,169 15.6 yrs £1,753
3 kW 2988 kWh 1793 kWh 1195 kWh £475 £120 £594 £8,204 13.8 yrs £3,680
4 kW 3984 kWh 2390 kWh 1593 kWh £633 £159 £792 £10,238 12.9 yrs £5,607
5 kW 4979 kWh 2988 kWh 1992 kWh £791 £199 £990 £12,273 12.4 yrs £7,534
6 kW 5975 kWh 3585 kWh 2390 kWh £949 £239 £1,188 £14,307 12.0 yrs £9,460
7 kW 6971 kWh 4183 kWh 2788 kWh £1,108 £279 £1,386 £16,342 11.8 yrs £11,387
8 kW 7967 kWh 4780 kWh 3187 kWh £1,266 £319 £1,585 £18,376 11.6 yrs £13,314

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: £1,072, Upfront: £13,673, 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 1394 kWh 598 kWh £369 £60 £429 £7,569 17.6 yrs £1,010
3 kW 2988 kWh 2091 kWh 896 kWh £554 £90 £643 £9,604 14.9 yrs £3,265
4 kW 3984 kWh 2788 kWh 1195 kWh £738 £120 £858 £11,638 13.6 yrs £5,520
5 kW 4979 kWh 3486 kWh 1494 kWh £923 £149 £1,072 £13,673 12.7 yrs £7,775
6 kW 5975 kWh 4183 kWh 1793 kWh £1,108 £179 £1,287 £15,707 12.2 yrs £10,030
7 kW 6971 kWh 4880 kWh 2091 kWh £1,292 £209 £1,501 £17,742 11.8 yrs £12,285
8 kW 7967 kWh 5577 kWh 2390 kWh £1,477 £239 £1,716 £19,776 11.5 yrs £14,540

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: £1,097, Upfront: £15,423, Break-even: 14.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1992 kWh 1454 kWh 538 kWh £385 £54 £439 £9,319 21.2 yrs £-543
3 kW 2988 kWh 2181 kWh 807 kWh £578 £81 £658 £11,354 17.2 yrs £1,810
4 kW 3984 kWh 2908 kWh 1076 kWh £770 £108 £878 £13,388 15.3 yrs £4,164
5 kW 4979 kWh 3635 kWh 1344 kWh £963 £134 £1,097 £15,423 14.1 yrs £6,517
6 kW 5975 kWh 4362 kWh 1613 kWh £1,155 £161 £1,316 £17,457 13.3 yrs £8,871
7 kW 6971 kWh 5089 kWh 1882 kWh £1,348 £188 £1,536 £19,492 12.7 yrs £11,224
8 kW 7967 kWh 5816 kWh 2151 kWh £1,540 £215 £1,755 £21,526 12.3 yrs £13,578

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: £1,113, Upfront: £17,173, Break-even: 15.4 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 £396 £50 £445 £11,069 24.9 yrs £-2,162
3 kW 2988 kWh 2241 kWh 747 kWh £593 £75 £668 £13,104 19.6 yrs £257
4 kW 3984 kWh 2988 kWh 996 kWh £791 £100 £891 £15,138 17.0 yrs £2,676
5 kW 4979 kWh 3735 kWh 1245 kWh £989 £124 £1,113 £17,173 15.4 yrs £5,096
6 kW 5975 kWh 4482 kWh 1494 kWh £1,187 £149 £1,336 £19,207 14.4 yrs £7,515
7 kW 6971 kWh 5228 kWh 1743 kWh £1,384 £174 £1,559 £21,242 13.6 yrs £9,934
8 kW 7967 kWh 5975 kWh 1992 kWh £1,582 £199 £1,781 £23,276 13.1 yrs £12,353

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: £1,130, Upfront: £19,623, Break-even: 17.4 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 £406 £46 £452 £13,519 29.9 yrs £-4,480
3 kW 2988 kWh 2301 kWh 687 kWh £609 £69 £678 £15,554 22.9 yrs £-1,996
4 kW 3984 kWh 3067 kWh 916 kWh £812 £92 £904 £17,588 19.5 yrs £489
5 kW 4979 kWh 3834 kWh 1145 kWh £1,015 £115 £1,130 £19,623 17.4 yrs £2,974
6 kW 5975 kWh 4601 kWh 1374 kWh £1,218 £137 £1,356 £21,657 16.0 yrs £5,459
7 kW 6971 kWh 5368 kWh 1603 kWh £1,421 £160 £1,582 £23,692 15.0 yrs £7,943
8 kW 7967 kWh 6135 kWh 1832 kWh £1,624 £183 £1,808 £25,726 14.2 yrs £10,428

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 TW3

Figures below are tailored to TW3 — click through for full league tables.

Big-Roof Britain Rank #2129 of 2182
3.8 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #895 of 2997
10.7 years (UK avg 11.3 years)
~£949 /yr • £10,173 upfront
Standing-Charge Drag Rank #793 of 2997
17.2% (UK avg 21.7%) drag on savings
£163 fixed • ~£949 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/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: 32% • Flats: 62% • Bungalows: 1% Based on 12,513 properties

Coverage

Hounslow (97%)|Richmond upon Thames (3%)

Areas Covered

Hounslow Central, Hounslow Heath, Hounslow South, Hounslow East, Hounslow West, Heston East, Heston Central, Whitton + 1 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 Southern

TW4 (Hounslow)
≈1.7 km away
Local sunshine: ~996 kWh/kWp · -0% vs TW3
TW5 (Hounslow)
≈1.8 km away
Local sunshine: ~996 kWh/kWp · +0% vs TW3
TW7 (Hounslow)
≈2.1 km away
Local sunshine: ~991 kWh/kWp · -0% vs TW3
UB2 (Ealing)
≈3.6 km away
Local sunshine: ~993 kWh/kWp · -0% vs TW3
TW8 (Hounslow)
≈4.0 km away
Local sunshine: ~991 kWh/kWp · -0% vs TW3
TW14 (Hounslow)
≈4.4 km away
Local sunshine: ~1,001 kWh/kWp · +0% vs TW3

Similar sunshine across the UK

GU21 (Woking)
~996 kWh/kWp · -0% vs TW3
PE30 (King's Lynn and West Norfolk)
~996 kWh/kWp · +0% vs TW3
LL66 (Isle of Anglesey)
~996 kWh/kWp · -0% vs TW3