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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in BN7 (Lewes)

See if solar pays off for you in Lewes — 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
10.8 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£944
What you save every year
Profit Over 25 Years
£13,427
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 South East, the current unit rate is 26.92p/kWh with a 47.60p/day standing charge. Your postcode’s south-facing sunshine yield is 1126 kWh/kW — 97 above the regional median (1029).

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 1126 kWh per year on a south-facing roof. We value self-used electricity at 26.9p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.9p/kWh
Standing charge
47.6p/day
Sunshine yield (south)
1126 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: £944, Upfront: £10,173, Break-even: 10.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2252 kWh 901 kWh 1351 kWh £242 £135 £378 £4,069 10.8 yrs £3,483
3 kW 3378 kWh 1351 kWh 2027 kWh £364 £203 £566 £6,104 10.8 yrs £5,224
4 kW 4504 kWh 1801 kWh 2702 kWh £485 £270 £755 £8,138 10.8 yrs £6,966
5 kW 5630 kWh 2252 kWh 3378 kWh £606 £338 £944 £10,173 10.8 yrs £8,707
6 kW 6756 kWh 2702 kWh 4053 kWh £727 £405 £1,133 £12,207 10.8 yrs £10,448
7 kW 7881 kWh 3153 kWh 4729 kWh £849 £473 £1,322 £14,242 10.8 yrs £12,190
8 kW 9007 kWh 3603 kWh 5404 kWh £970 £540 £1,510 £16,276 10.8 yrs £13,931

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: £1,134, Upfront: £12,273, Break-even: 10.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2252 kWh 1351 kWh 901 kWh £364 £90 £454 £6,169 13.6 yrs £2,907
3 kW 3378 kWh 2027 kWh 1351 kWh £546 £135 £681 £8,204 12.1 yrs £5,410
4 kW 4504 kWh 2702 kWh 1801 kWh £727 £180 £908 £10,238 11.3 yrs £7,914
5 kW 5630 kWh 3378 kWh 2252 kWh £909 £225 £1,134 £12,273 10.8 yrs £10,417
6 kW 6756 kWh 4053 kWh 2702 kWh £1,091 £270 £1,361 £14,307 10.5 yrs £12,920
7 kW 7881 kWh 4729 kWh 3153 kWh £1,273 £315 £1,588 £16,342 10.3 yrs £15,424
8 kW 9007 kWh 5404 kWh 3603 kWh £1,455 £360 £1,815 £18,376 10.1 yrs £17,927

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: £1,230, Upfront: £13,673, 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 2252 kWh 1576 kWh 676 kWh £424 £68 £492 £7,569 15.4 yrs £2,269
3 kW 3378 kWh 2364 kWh 1013 kWh £637 £101 £738 £9,604 13.0 yrs £5,153
4 kW 4504 kWh 3153 kWh 1351 kWh £849 £135 £984 £11,638 11.8 yrs £8,038
5 kW 5630 kWh 3941 kWh 1689 kWh £1,061 £169 £1,230 £13,673 11.1 yrs £10,922
6 kW 6756 kWh 4729 kWh 2027 kWh £1,273 £203 £1,476 £15,707 10.6 yrs £13,806
7 kW 7881 kWh 5517 kWh 2364 kWh £1,485 £236 £1,722 £17,742 10.3 yrs £16,691
8 kW 9007 kWh 6305 kWh 2702 kWh £1,697 £270 £1,968 £19,776 10.1 yrs £19,575

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: £1,258, Upfront: £15,423, 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 2252 kWh 1644 kWh 608 kWh £443 £61 £503 £9,319 18.5 yrs £747
3 kW 3378 kWh 2466 kWh 912 kWh £664 £91 £755 £11,354 15.0 yrs £3,746
4 kW 4504 kWh 3288 kWh 1216 kWh £885 £122 £1,007 £13,388 13.3 yrs £6,745
5 kW 5630 kWh 4110 kWh 1520 kWh £1,106 £152 £1,258 £15,423 12.3 yrs £9,744
6 kW 6756 kWh 4932 kWh 1824 kWh £1,328 £182 £1,510 £17,457 11.6 yrs £12,742
7 kW 7881 kWh 5753 kWh 2128 kWh £1,549 £213 £1,762 £19,492 11.1 yrs £15,741
8 kW 9007 kWh 6575 kWh 2432 kWh £1,770 £243 £2,013 £21,526 10.7 yrs £18,740

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: £1,277, Upfront: £17,173, Break-even: 13.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2252 kWh 1689 kWh 563 kWh £455 £56 £511 £11,069 21.7 yrs £-850
3 kW 3378 kWh 2533 kWh 844 kWh £682 £84 £766 £13,104 17.1 yrs £2,225
4 kW 4504 kWh 3378 kWh 1126 kWh £909 £113 £1,022 £15,138 14.8 yrs £5,300
5 kW 5630 kWh 4222 kWh 1407 kWh £1,137 £141 £1,277 £17,173 13.4 yrs £8,375
6 kW 6756 kWh 5067 kWh 1689 kWh £1,364 £169 £1,533 £19,207 12.5 yrs £11,449
7 kW 7881 kWh 5911 kWh 1970 kWh £1,591 £197 £1,788 £21,242 11.9 yrs £14,524
8 kW 9007 kWh 6756 kWh 2252 kWh £1,819 £225 £2,044 £23,276 11.4 yrs £17,599

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: £1,296, Upfront: £19,623, Break-even: 15.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2252 kWh 1734 kWh 518 kWh £467 £52 £519 £13,519 26.1 yrs £-3,148
3 kW 3378 kWh 2601 kWh 777 kWh £700 £78 £778 £15,554 20.0 yrs £3
4 kW 4504 kWh 3468 kWh 1036 kWh £934 £104 £1,037 £17,588 17.0 yrs £3,154
5 kW 5630 kWh 4335 kWh 1295 kWh £1,167 £129 £1,296 £19,623 15.1 yrs £6,306
6 kW 6756 kWh 5202 kWh 1554 kWh £1,400 £155 £1,556 £21,657 13.9 yrs £9,457
7 kW 7881 kWh 6069 kWh 1813 kWh £1,634 £181 £1,815 £23,692 13.1 yrs £12,608
8 kW 9007 kWh 6936 kWh 2072 kWh £1,867 £207 £2,074 £25,726 12.4 yrs £15,759

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 BN7

Figures below are tailored to BN7 — click through for full league tables.

Big-Roof Britain Rank #1481 of 2182
4.7 kWp (UK avg 5.1 kWp)
~10 panels (≈430 W)
Solar Payback Index Rank #22 of 2997
9.4 years (UK avg 11.3 years)
~£1,087 /yr • £10,173 upfront
Standing-Charge Drag Rank #556 of 2997
16.0% (UK avg 21.7%) drag on savings
£174 fixed • ~£1,087 /yr value

Your Area at a Glance

Your Electricity Rate
26.92p/kWh
Daily Fixed Charge
47.60p/day
Local Sunshine
1126kWh/kW
A 1 kW system generates ~1126 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: 66% • Flats: 26% • Bungalows: 5% Based on 5,206 properties

Coverage

Lewes (100%)

Areas Covered

Lewes Bridge, Lewes Priory, Lewes Castle, Plumpton, Streat, East Chiltington & St John, Kingston, Chailey + 2 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 South East

BN8 (Lewes)
≈3.7 km away
Local sunshine: ~1,067 kWh/kWp · -5% vs BN7
BN10 (Lewes)
≈9.3 km away
Local sunshine: ~1,123 kWh/kWp · -0% vs BN7
BN51 (Brighton and Hove)
≈9.5 km away
Local sunshine: ~1,137 kWh/kWp · +1% vs BN7
BN9 (Lewes)
≈9.6 km away
Local sunshine: ~1,138 kWh/kWp · +1% vs BN7
BN2 (Brighton and Hove)
≈10.9 km away
Local sunshine: ~1,120 kWh/kWp · -1% vs BN7
BN1 (Brighton and Hove)
≈12.0 km away
Local sunshine: ~1,118 kWh/kWp · -1% vs BN7

Similar sunshine across the UK

PO38 (Isle of Wight)
~1,125 kWh/kWp · -0% vs BN7
PO22 (Arun)
~1,128 kWh/kWp · +0% vs BN7
TQ7 (South Hams)
~1,123 kWh/kWp · -0% vs BN7