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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in WD24 (Watford)

See if solar pays off for you in Watford — 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
£818
What you save every year
Profit Over 25 Years
£10,276
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 985 kWh/kW — 24 below the regional median (1009).

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 985 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)
985 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: £818, 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 1970 kWh 788 kWh 1182 kWh £209 £118 £327 £4,069 12.4 yrs £2,474
3 kW 2954 kWh 1182 kWh 1773 kWh £314 £177 £491 £6,104 12.4 yrs £3,712
4 kW 3939 kWh 1576 kWh 2363 kWh £418 £236 £654 £8,138 12.4 yrs £4,949
5 kW 4924 kWh 1970 kWh 2954 kWh £523 £295 £818 £10,173 12.4 yrs £6,186
6 kW 5908 kWh 2363 kWh 3545 kWh £627 £355 £982 £12,207 12.4 yrs £7,423
7 kW 6893 kWh 2757 kWh 4136 kWh £732 £414 £1,145 £14,242 12.4 yrs £8,661
8 kW 7878 kWh 3151 kWh 4727 kWh £836 £473 £1,309 £16,276 12.4 yrs £9,898

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 1970 kWh 1182 kWh 788 kWh £314 £79 £392 £6,169 15.7 yrs £1,677
3 kW 2954 kWh 1773 kWh 1182 kWh £470 £118 £588 £8,204 13.9 yrs £3,565
4 kW 3939 kWh 2363 kWh 1576 kWh £627 £158 £785 £10,238 13.0 yrs £5,453
5 kW 4924 kWh 2954 kWh 1970 kWh £784 £197 £981 £12,273 12.5 yrs £7,342
6 kW 5908 kWh 3545 kWh 2363 kWh £941 £236 £1,177 £14,307 12.2 yrs £9,230
7 kW 6893 kWh 4136 kWh 2757 kWh £1,097 £276 £1,373 £16,342 11.9 yrs £11,118
8 kW 7878 kWh 4727 kWh 3151 kWh £1,254 £315 £1,569 £18,376 11.7 yrs £13,007

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: £1,062, 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 1970 kWh 1379 kWh 591 kWh £366 £59 £425 £7,569 17.8 yrs £928
3 kW 2954 kWh 2068 kWh 886 kWh £549 £89 £637 £9,604 15.1 yrs £3,142
4 kW 3939 kWh 2757 kWh 1182 kWh £732 £118 £850 £11,638 13.7 yrs £5,356
5 kW 4924 kWh 3447 kWh 1477 kWh £914 £148 £1,062 £13,673 12.9 yrs £7,569
6 kW 5908 kWh 4136 kWh 1773 kWh £1,097 £177 £1,275 £15,707 12.3 yrs £9,783
7 kW 6893 kWh 4825 kWh 2068 kWh £1,280 £207 £1,487 £17,742 11.9 yrs £11,997
8 kW 7878 kWh 5515 kWh 2363 kWh £1,463 £236 £1,699 £19,776 11.6 yrs £14,211

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: £1,087, 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 1970 kWh 1438 kWh 532 kWh £381 £53 £435 £9,319 21.4 yrs £-627
3 kW 2954 kWh 2157 kWh 798 kWh £572 £80 £652 £11,354 17.4 yrs £1,685
4 kW 3939 kWh 2875 kWh 1064 kWh £763 £106 £869 £13,388 15.4 yrs £3,996
5 kW 4924 kWh 3594 kWh 1329 kWh £954 £133 £1,087 £15,423 14.2 yrs £6,308
6 kW 5908 kWh 4313 kWh 1595 kWh £1,144 £160 £1,304 £17,457 13.4 yrs £8,619
7 kW 6893 kWh 5032 kWh 1861 kWh £1,335 £186 £1,521 £19,492 12.8 yrs £10,931
8 kW 7878 kWh 5751 kWh 2127 kWh £1,526 £213 £1,738 £21,526 12.4 yrs £13,243

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: £1,103, 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 1970 kWh 1477 kWh 492 kWh £392 £49 £441 £11,069 25.1 yrs £-2,247
3 kW 2954 kWh 2216 kWh 739 kWh £588 £74 £662 £13,104 19.8 yrs £130
4 kW 3939 kWh 2954 kWh 985 kWh £784 £98 £882 £15,138 17.2 yrs £2,507
5 kW 4924 kWh 3693 kWh 1231 kWh £980 £123 £1,103 £17,173 15.6 yrs £4,883
6 kW 5908 kWh 4431 kWh 1477 kWh £1,176 £148 £1,323 £19,207 14.5 yrs £7,260
7 kW 6893 kWh 5170 kWh 1723 kWh £1,372 £172 £1,544 £21,242 13.8 yrs £9,637
8 kW 7878 kWh 5908 kWh 1970 kWh £1,568 £197 £1,764 £23,276 13.2 yrs £12,013

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: £1,119, Upfront: £19,623, Break-even: 17.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1970 kWh 1517 kWh 453 kWh £402 £45 £448 £13,519 30.2 yrs £-4,566
3 kW 2954 kWh 2275 kWh 679 kWh £603 £68 £671 £15,554 23.2 yrs £-2,125
4 kW 3939 kWh 3033 kWh 906 kWh £805 £91 £895 £17,588 19.6 yrs £317
5 kW 4924 kWh 3791 kWh 1132 kWh £1,006 £113 £1,119 £19,623 17.5 yrs £2,759
6 kW 5908 kWh 4550 kWh 1359 kWh £1,207 £136 £1,343 £21,657 16.1 yrs £5,201
7 kW 6893 kWh 5308 kWh 1585 kWh £1,408 £159 £1,567 £23,692 15.1 yrs £7,643
8 kW 7878 kWh 6066 kWh 1812 kWh £1,609 £181 £1,791 £25,726 14.4 yrs £10,084

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 WD24

Figures below are tailored to WD24 — click through for full league tables.

Big-Roof Britain Rank #1995 of 2182
4.1 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #1092 of 2997
10.8 years (UK avg 11.3 years)
~£940 /yr • £10,173 upfront
Standing-Charge Drag Rank #1210 of 2997
18.7% (UK avg 21.7%) drag on savings
£176 fixed • ~£940 /yr value

Your Area at a Glance

Your Electricity Rate
26.53p/kWh
Daily Fixed Charge
48.25p/day
Local Sunshine
985kWh/kW
A 1 kW system generates ~985 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: 56% • Flats: 38% • Bungalows: 2% Based on 6,554 properties

Coverage

Watford (100%)

Areas Covered

Tudor, Callowland, Leggatts, Holywell, Woodside, Central, Nascot, Stanborough

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

WD2 (Watford)
≈1.0 km away
Local sunshine: ~992 kWh/kWp · +1% vs WD24
WD17 (Watford)
≈1.3 km away
Local sunshine: ~985 kWh/kWp · -0% vs WD24
WD25 (Watford)
≈1.7 km away
Local sunshine: ~988 kWh/kWp · +0% vs WD24
WD1 (Watford)
≈2.3 km away
Local sunshine: ~991 kWh/kWp · +1% vs WD24
WD99 (Watford)
≈3.1 km away
Local sunshine: ~991 kWh/kWp · +1% vs WD24
WD18 (Watford)
≈3.1 km away
Local sunshine: ~985 kWh/kWp · -0% vs WD24

Similar sunshine across the UK

CF15 (Cardiff)
~985 kWh/kWp · +0% vs WD24
LN1 (Lincoln)
~985 kWh/kWp · -0% vs WD24
LN4 (North Kesteven)
~985 kWh/kWp · +0% vs WD24