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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TN14 (Sevenoaks)

See if solar pays off for you in Sevenoaks — 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
11.9 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£1,030
What you save every year
Profit Over 25 Years
£13,534
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 1023 kWh/kW — 6 below the regional median (1029).

Read the full story

A typical roof here lands around 6.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 1023 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)
1023 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: £858, Upfront: £10,173, Break-even: 11.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2047 kWh 819 kWh 1228 kWh £220 £123 £343 £4,069 11.9 yrs £2,795
3 kW 3070 kWh 1228 kWh 1842 kWh £331 £184 £515 £6,104 11.9 yrs £4,193
4 kW 4094 kWh 1637 kWh 2456 kWh £441 £246 £686 £8,138 11.9 yrs £5,590
5 kW 5117 kWh 2047 kWh 3070 kWh £551 £307 £858 £10,173 11.9 yrs £6,988
6 kW 6140 kWh 2456 kWh 3684 kWh £661 £368 £1,030 £12,207 11.9 yrs £8,386
7 kW 7164 kWh 2866 kWh 4298 kWh £771 £430 £1,201 £14,242 11.9 yrs £9,783
8 kW 8187 kWh 3275 kWh 4912 kWh £882 £491 £1,373 £16,276 11.9 yrs £11,181

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: £1,031, Upfront: £12,273, Break-even: 11.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2047 kWh 1228 kWh 819 kWh £331 £82 £412 £6,169 15.0 yrs £2,080
3 kW 3070 kWh 1842 kWh 1228 kWh £496 £123 £619 £8,204 13.3 yrs £4,171
4 kW 4094 kWh 2456 kWh 1637 kWh £661 £164 £825 £10,238 12.4 yrs £6,261
5 kW 5117 kWh 3070 kWh 2047 kWh £827 £205 £1,031 £12,273 11.9 yrs £8,351
6 kW 6140 kWh 3684 kWh 2456 kWh £992 £246 £1,237 £14,307 11.6 yrs £10,441
7 kW 7164 kWh 4298 kWh 2866 kWh £1,157 £287 £1,444 £16,342 11.3 yrs £12,532
8 kW 8187 kWh 4912 kWh 3275 kWh £1,322 £327 £1,650 £18,376 11.1 yrs £14,622

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: £1,118, Upfront: £13,673, Break-even: 12.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2047 kWh 1433 kWh 614 kWh £386 £61 £447 £7,569 16.9 yrs £1,373
3 kW 3070 kWh 2149 kWh 921 kWh £579 £92 £671 £9,604 14.3 yrs £3,810
4 kW 4094 kWh 2866 kWh 1228 kWh £771 £123 £894 £11,638 13.0 yrs £6,246
5 kW 5117 kWh 3582 kWh 1535 kWh £964 £154 £1,118 £13,673 12.2 yrs £8,683
6 kW 6140 kWh 4298 kWh 1842 kWh £1,157 £184 £1,341 £15,707 11.7 yrs £11,119
7 kW 7164 kWh 5015 kWh 2149 kWh £1,350 £215 £1,565 £17,742 11.3 yrs £13,556
8 kW 8187 kWh 5731 kWh 2456 kWh £1,543 £246 £1,788 £19,776 11.1 yrs £15,993

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: £1,144, Upfront: £15,423, Break-even: 13.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2047 kWh 1494 kWh 553 kWh £402 £55 £457 £9,319 20.4 yrs £-169
3 kW 3070 kWh 2241 kWh 829 kWh £603 £83 £686 £11,354 16.5 yrs £2,371
4 kW 4094 kWh 2988 kWh 1105 kWh £804 £111 £915 £13,388 14.6 yrs £4,912
5 kW 5117 kWh 3735 kWh 1382 kWh £1,006 £138 £1,144 £15,423 13.5 yrs £7,452
6 kW 6140 kWh 4483 kWh 1658 kWh £1,207 £166 £1,372 £17,457 12.7 yrs £9,993
7 kW 7164 kWh 5230 kWh 1934 kWh £1,408 £193 £1,601 £19,492 12.2 yrs £12,533
8 kW 8187 kWh 5977 kWh 2211 kWh £1,609 £221 £1,830 £21,526 11.8 yrs £15,074

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: £1,161, Upfront: £17,173, Break-even: 14.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2047 kWh 1535 kWh 512 kWh £413 £51 £464 £11,069 23.8 yrs £-1,781
3 kW 3070 kWh 2303 kWh 768 kWh £620 £77 £697 £13,104 18.8 yrs £829
4 kW 4094 kWh 3070 kWh 1023 kWh £827 £102 £929 £15,138 16.3 yrs £3,439
5 kW 5117 kWh 3838 kWh 1279 kWh £1,033 £128 £1,161 £17,173 14.8 yrs £6,049
6 kW 6140 kWh 4605 kWh 1535 kWh £1,240 £154 £1,393 £19,207 13.8 yrs £8,658
7 kW 7164 kWh 5373 kWh 1791 kWh £1,446 £179 £1,625 £21,242 13.1 yrs £11,268
8 kW 8187 kWh 6140 kWh 2047 kWh £1,653 £205 £1,858 £23,276 12.5 yrs £13,878

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: £1,178, Upfront: £19,623, Break-even: 16.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2047 kWh 1576 kWh 471 kWh £424 £47 £471 £13,519 28.7 yrs £-4,092
3 kW 3070 kWh 2364 kWh 706 kWh £636 £71 £707 £15,554 22.0 yrs £-1,413
4 kW 4094 kWh 3152 kWh 942 kWh £849 £94 £943 £17,588 18.7 yrs £1,266
5 kW 5117 kWh 3940 kWh 1177 kWh £1,061 £118 £1,178 £19,623 16.7 yrs £3,945
6 kW 6140 kWh 4728 kWh 1412 kWh £1,273 £141 £1,414 £21,657 15.3 yrs £6,624
7 kW 7164 kWh 5516 kWh 1648 kWh £1,485 £165 £1,650 £23,692 14.4 yrs £9,303
8 kW 8187 kWh 6304 kWh 1883 kWh £1,697 £188 £1,885 £25,726 13.6 yrs £11,982

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 TN14

Figures below are tailored to TN14 — click through for full league tables.

Big-Roof Britain Rank #373 of 2182
5.8 kWp (UK avg 5.1 kWp)
~12 panels (≈430 W)
Solar Payback Index Rank #367 of 2997
10.3 years (UK avg 11.3 years)
~£1,185 /yr • £12,207 upfront
Standing-Charge Drag Rank #209 of 2997
14.7% (UK avg 21.7%) drag on savings
£174 fixed • ~£1,185 /yr value

Your Area at a Glance

Your Electricity Rate
26.92p/kWh
Daily Fixed Charge
47.60p/day
Local Sunshine
1023kWh/kW
A 1 kW system generates ~1023 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
6.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 70% • Flats: 18% • Bungalows: 10% Based on 3,883 properties

Coverage

Sevenoaks (96%)|Bromley (4%)

Areas Covered

Otford and Shoreham, Halstead, Knockholt and Badgers Mount, Brasted, Chevening and Sundridge, Sevenoaks Town and St John's, Sevenoaks Northern, Seal and Weald + 6 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

TN13 (Sevenoaks)
≈3.3 km away
Local sunshine: ~1,015 kWh/kWp · -1% vs TN14
TN15 (Sevenoaks)
≈6.8 km away
Local sunshine: ~1,023 kWh/kWp · -0% vs TN14
BR6 (Bromley)
≈9.7 km away
Local sunshine: ~1,010 kWh/kWp · -1% vs TN14
TN16 (Bromley)
≈9.8 km away
Local sunshine: ~1,009 kWh/kWp · -1% vs TN14
BR8 (Sevenoaks)
≈10.9 km away
Local sunshine: ~1,010 kWh/kWp · -1% vs TN14
BR5 (Bromley)
≈11.2 km away
Local sunshine: ~1,011 kWh/kWp · -1% vs TN14

Similar sunshine across the UK

RM20 (Thurrock)
~1,023 kWh/kWp · -0% vs TN14
SO50 (Eastleigh)
~1,024 kWh/kWp · +0% vs TN14
SO53 (Eastleigh)
~1,024 kWh/kWp · +0% vs TN14