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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in HA1 (Harrow)

See if solar pays off for you in Harrow — 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
£6,104
What you pay to get started
Annual Benefit
£494
What you save every year
Profit Over 25 Years
£6,248
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 Eastern, the current unit rate is 26.53p/kWh with a 48.25p/day standing charge. Your postcode’s south-facing sunshine yield is 991 kWh/kW — 18 below the regional median (1009).

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 991 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
48.2p/day
Sunshine yield (south)
991 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 1983 kWh 793 kWh 1190 kWh £210 £119 £329 £4,069 12.4 yrs £2,519
3 kW 2974 kWh 1190 kWh 1785 kWh £316 £178 £494 £6,104 12.4 yrs £3,778
4 kW 3966 kWh 1586 kWh 2379 kWh £421 £238 £659 £8,138 12.4 yrs £5,037
5 kW 4957 kWh 1983 kWh 2974 kWh £526 £297 £823 £10,173 12.4 yrs £6,297
6 kW 5948 kWh 2379 kWh 3569 kWh £631 £357 £988 £12,207 12.4 yrs £7,556
7 kW 6940 kWh 2776 kWh 4164 kWh £736 £416 £1,153 £14,242 12.4 yrs £8,815
8 kW 7931 kWh 3172 kWh 4759 kWh £842 £476 £1,318 £16,276 12.4 yrs £10,075

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: £987, 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 1983 kWh 1190 kWh 793 kWh £316 £79 £395 £6,169 15.6 yrs £1,730
3 kW 2974 kWh 1785 kWh 1190 kWh £473 £119 £592 £8,204 13.8 yrs £3,644
4 kW 3966 kWh 2379 kWh 1586 kWh £631 £159 £790 £10,238 13.0 yrs £5,559
5 kW 4957 kWh 2974 kWh 1983 kWh £789 £198 £987 £12,273 12.4 yrs £7,474
6 kW 5948 kWh 3569 kWh 2379 kWh £947 £238 £1,185 £14,307 12.1 yrs £9,389
7 kW 6940 kWh 4164 kWh 2776 kWh £1,105 £278 £1,382 £16,342 11.8 yrs £11,304
8 kW 7931 kWh 4759 kWh 3172 kWh £1,262 £317 £1,580 £18,376 11.6 yrs £13,219

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: £1,069, Upfront: £13,673, Break-even: 12.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1983 kWh 1388 kWh 595 kWh £368 £59 £428 £7,569 17.7 yrs £985
3 kW 2974 kWh 2082 kWh 892 kWh £552 £89 £642 £9,604 15.0 yrs £3,228
4 kW 3966 kWh 2776 kWh 1190 kWh £736 £119 £855 £11,638 13.6 yrs £5,470
5 kW 4957 kWh 3470 kWh 1487 kWh £921 £149 £1,069 £13,673 12.8 yrs £7,713
6 kW 5948 kWh 4164 kWh 1785 kWh £1,105 £178 £1,283 £15,707 12.2 yrs £9,956
7 kW 6940 kWh 4858 kWh 2082 kWh £1,289 £208 £1,497 £17,742 11.9 yrs £12,198
8 kW 7931 kWh 5552 kWh 2379 kWh £1,473 £238 £1,711 £19,776 11.6 yrs £14,441

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: £1,094, 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 1983 kWh 1447 kWh 535 kWh £384 £54 £438 £9,319 21.3 yrs £-568
3 kW 2974 kWh 2171 kWh 803 kWh £576 £80 £656 £11,354 17.3 yrs £1,773
4 kW 3966 kWh 2895 kWh 1071 kWh £768 £107 £875 £13,388 15.3 yrs £4,114
5 kW 4957 kWh 3619 kWh 1338 kWh £960 £134 £1,094 £15,423 14.1 yrs £6,455
6 kW 5948 kWh 4342 kWh 1606 kWh £1,152 £161 £1,313 £17,457 13.3 yrs £8,795
7 kW 6940 kWh 5066 kWh 1874 kWh £1,344 £187 £1,531 £19,492 12.7 yrs £11,136
8 kW 7931 kWh 5790 kWh 2141 kWh £1,536 £214 £1,750 £21,526 12.3 yrs £13,477

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: £1,110, Upfront: £17,173, Break-even: 15.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1983 kWh 1487 kWh 496 kWh £395 £50 £444 £11,069 24.9 yrs £-2,187
3 kW 2974 kWh 2231 kWh 744 kWh £592 £74 £666 £13,104 19.7 yrs £219
4 kW 3966 kWh 2974 kWh 991 kWh £789 £99 £888 £15,138 17.0 yrs £2,626
5 kW 4957 kWh 3718 kWh 1239 kWh £986 £124 £1,110 £17,173 15.5 yrs £5,032
6 kW 5948 kWh 4461 kWh 1487 kWh £1,184 £149 £1,332 £19,207 14.4 yrs £7,439
7 kW 6940 kWh 5205 kWh 1735 kWh £1,381 £173 £1,554 £21,242 13.7 yrs £9,845
8 kW 7931 kWh 5948 kWh 1983 kWh £1,578 £198 £1,776 £23,276 13.1 yrs £12,252

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: £1,127, 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 1983 kWh 1527 kWh 456 kWh £405 £46 £451 £13,519 30.0 yrs £-4,506
3 kW 2974 kWh 2290 kWh 684 kWh £608 £68 £676 £15,554 23.0 yrs £-2,034
4 kW 3966 kWh 3054 kWh 912 kWh £810 £91 £901 £17,588 19.5 yrs £438
5 kW 4957 kWh 3817 kWh 1140 kWh £1,013 £114 £1,127 £19,623 17.4 yrs £2,910
6 kW 5948 kWh 4580 kWh 1368 kWh £1,215 £137 £1,352 £21,657 16.0 yrs £5,382
7 kW 6940 kWh 5344 kWh 1596 kWh £1,418 £160 £1,577 £23,692 15.0 yrs £7,854
8 kW 7931 kWh 6107 kWh 1824 kWh £1,620 £182 £1,803 £25,726 14.3 yrs £10,326

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 HA1

Figures below are tailored to HA1 — click through for full league tables.

Big-Roof Britain Rank #2146 of 2182
3.7 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #802 of 2997
10.7 years (UK avg 11.3 years)
~£1,136 /yr • £12,207 upfront
Standing-Charge Drag Rank #492 of 2997
15.5% (UK avg 21.7%) drag on savings
£176 fixed • ~£1,136 /yr value

Your Area at a Glance

Your Electricity Rate
26.53p/kWh
Daily Fixed Charge
48.25p/day
Local Sunshine
991kWh/kW
A 1 kW system generates ~991 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
3.0kW
For eligible homes 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: 22% • Flats: 74% • Bungalows: 1% Based on 15,242 properties

Coverage

Harrow (97%)|Brent (3%)

Areas Covered

Greenhill, Marlborough, Harrow on the Hill, Headstone, West Harrow, Northwick Park, North Harrow

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 Eastern

HA3 (Harrow)
≈0.5 km away
Local sunshine: ~992 kWh/kWp · +0% vs HA1
HA2 (Harrow)
≈2.0 km away
Local sunshine: ~992 kWh/kWp · +0% vs HA1
HA7 (Harrow)
≈3.1 km away
Local sunshine: ~990 kWh/kWp · -0% vs HA1
HA5 (Harrow)
≈3.7 km away
Local sunshine: ~993 kWh/kWp · +0% vs HA1
HA0 (Brent)
≈4.2 km away
Local sunshine: ~992 kWh/kWp · +0% vs HA1
HA9 (Brent)
≈4.3 km away
Local sunshine: ~991 kWh/kWp · -0% vs HA1

Similar sunshine across the UK

SL5 (Windsor and Maidenhead)
~991 kWh/kWp · -0% vs HA1
E14 (Tower Hamlets)
~991 kWh/kWp · -0% vs HA1
W13 (Ealing)
~991 kWh/kWp · -0% vs HA1