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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in HP21 (Buckinghamshire)

See if solar pays off for you in Buckinghamshire — 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
£8,138
What you pay to get started
Annual Benefit
£654
What you save every year
Profit Over 25 Years
£8,204
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 984 kWh/kW — 25 below the regional median (1009).

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 984 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)
984 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: £817, 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 1967 kWh 787 kWh 1180 kWh £209 £118 £327 £4,069 12.4 yrs £2,468
3 kW 2951 kWh 1180 kWh 1771 kWh £313 £177 £490 £6,104 12.4 yrs £3,702
4 kW 3935 kWh 1574 kWh 2361 kWh £418 £236 £654 £8,138 12.4 yrs £4,935
5 kW 4919 kWh 1967 kWh 2951 kWh £522 £295 £817 £10,173 12.4 yrs £6,169
6 kW 5902 kWh 2361 kWh 3541 kWh £626 £354 £981 £12,207 12.4 yrs £7,403
7 kW 6886 kWh 2754 kWh 4132 kWh £731 £413 £1,144 £14,242 12.4 yrs £8,637
8 kW 7870 kWh 3148 kWh 4722 kWh £835 £472 £1,307 £16,276 12.4 yrs £9,871

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: £980, 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 1967 kWh 1180 kWh 787 kWh £313 £79 £392 £6,169 15.7 yrs £1,669
3 kW 2951 kWh 1771 kWh 1180 kWh £470 £118 £588 £8,204 14.0 yrs £3,553
4 kW 3935 kWh 2361 kWh 1574 kWh £626 £157 £784 £10,238 13.1 yrs £5,437
5 kW 4919 kWh 2951 kWh 1967 kWh £783 £197 £980 £12,273 12.5 yrs £7,321
6 kW 5902 kWh 3541 kWh 2361 kWh £940 £236 £1,176 £14,307 12.2 yrs £9,206
7 kW 6886 kWh 4132 kWh 2754 kWh £1,096 £275 £1,372 £16,342 11.9 yrs £11,090
8 kW 7870 kWh 4722 kWh 3148 kWh £1,253 £315 £1,568 £18,376 11.7 yrs £12,974

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: £1,061, 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 1967 kWh 1377 kWh 590 kWh £365 £59 £424 £7,569 17.8 yrs £919
3 kW 2951 kWh 2066 kWh 885 kWh £548 £89 £637 £9,604 15.1 yrs £3,128
4 kW 3935 kWh 2754 kWh 1180 kWh £731 £118 £849 £11,638 13.7 yrs £5,338
5 kW 4919 kWh 3443 kWh 1476 kWh £913 £148 £1,061 £13,673 12.9 yrs £7,547
6 kW 5902 kWh 4132 kWh 1771 kWh £1,096 £177 £1,273 £15,707 12.3 yrs £9,757
7 kW 6886 kWh 4820 kWh 2066 kWh £1,279 £207 £1,485 £17,742 11.9 yrs £11,966
8 kW 7870 kWh 5509 kWh 2361 kWh £1,462 £236 £1,698 £19,776 11.6 yrs £14,176

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: £1,085, 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 1967 kWh 1436 kWh 531 kWh £381 £53 £434 £9,319 21.5 yrs £-636
3 kW 2951 kWh 2154 kWh 797 kWh £572 £80 £651 £11,354 17.4 yrs £1,671
4 kW 3935 kWh 2872 kWh 1062 kWh £762 £106 £868 £13,388 15.4 yrs £3,978
5 kW 4919 kWh 3591 kWh 1328 kWh £953 £133 £1,085 £15,423 14.2 yrs £6,285
6 kW 5902 kWh 4309 kWh 1594 kWh £1,143 £159 £1,302 £17,457 13.4 yrs £8,592
7 kW 6886 kWh 5027 kWh 1859 kWh £1,334 £186 £1,520 £19,492 12.8 yrs £10,899
8 kW 7870 kWh 5745 kWh 2125 kWh £1,524 £212 £1,737 £21,526 12.4 yrs £13,207

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: £1,102, 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 1967 kWh 1476 kWh 492 kWh £391 £49 £441 £11,069 25.1 yrs £-2,256
3 kW 2951 kWh 2213 kWh 738 kWh £587 £74 £661 £13,104 19.8 yrs £116
4 kW 3935 kWh 2951 kWh 984 kWh £783 £98 £881 £15,138 17.2 yrs £2,488
5 kW 4919 kWh 3689 kWh 1230 kWh £979 £123 £1,102 £17,173 15.6 yrs £4,861
6 kW 5902 kWh 4427 kWh 1476 kWh £1,174 £148 £1,322 £19,207 14.5 yrs £7,233
7 kW 6886 kWh 5165 kWh 1722 kWh £1,370 £172 £1,542 £21,242 13.8 yrs £9,605
8 kW 7870 kWh 5902 kWh 1967 kWh £1,566 £197 £1,763 £23,276 13.2 yrs £11,977

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: £1,118, Upfront: £19,623, Break-even: 17.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1967 kWh 1515 kWh 453 kWh £402 £45 £447 £13,519 30.2 yrs £-4,576
3 kW 2951 kWh 2272 kWh 679 kWh £603 £68 £671 £15,554 23.2 yrs £-2,139
4 kW 3935 kWh 3030 kWh 905 kWh £804 £91 £894 £17,588 19.7 yrs £299
5 kW 4919 kWh 3787 kWh 1131 kWh £1,005 £113 £1,118 £19,623 17.6 yrs £2,736
6 kW 5902 kWh 4545 kWh 1358 kWh £1,206 £136 £1,341 £21,657 16.1 yrs £5,173
7 kW 6886 kWh 5302 kWh 1584 kWh £1,407 £158 £1,565 £23,692 15.1 yrs £7,610
8 kW 7870 kWh 6060 kWh 1810 kWh £1,608 £181 £1,789 £25,726 14.4 yrs £10,047

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 HP21

Figures below are tailored to HP21 — click through for full league tables.

Big-Roof Britain Rank #1847 of 2182
4.4 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #967 of 2997
10.8 years (UK avg 11.3 years)
~£751 /yr • £8,138 upfront
Standing-Charge Drag Rank #2111 of 2997
23.5% (UK avg 21.7%) drag on savings
£176 fixed • ~£751 /yr value

Your Area at a Glance

Your Electricity Rate
26.53p/kWh
Daily Fixed Charge
48.25p/day
Local Sunshine
984kWh/kW
A 1 kW system generates ~984 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: 67% • Flats: 26% • Bungalows: 4% Based on 8,682 properties

Coverage

Buckinghamshire (100%)

Areas Covered

Aylesbury South East, Aylesbury South West, Aylesbury North, Aylesbury East, Aylesbury West, Haddenham & Stone, Wendover, Halton & Stoke Mandeville

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

HP20 (Buckinghamshire)
≈1.3 km away
Local sunshine: ~982 kWh/kWp · -0% vs HP21
HP19 (Buckinghamshire)
≈2.2 km away
Local sunshine: ~982 kWh/kWp · -0% vs HP21
HP22 (Buckinghamshire)
≈3.6 km away
Local sunshine: ~983 kWh/kWp · -0% vs HP21
HP17 (Buckinghamshire)
≈6.6 km away
Local sunshine: ~971 kWh/kWp · -1% vs HP21
HP27 (Buckinghamshire)
≈9.5 km away
Local sunshine: ~971 kWh/kWp · -1% vs HP21
HP23 (Dacorum)
≈9.8 km away
Local sunshine: ~980 kWh/kWp · -0% vs HP21

Similar sunshine across the UK

OX49 (South Oxfordshire)
~984 kWh/kWp · +0% vs HP21
CV33 (Stratford-on-Avon)
~984 kWh/kWp · +0% vs HP21
SA61 (Pembrokeshire)
~984 kWh/kWp · -0% vs HP21