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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TN9 (Tonbridge and Malling)

See if solar pays off for you in Tonbridge and Malling — 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
11.8 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£862
What you save every year
Profit Over 25 Years
£11,371
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 1028 kWh/kW — 1 below 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 1028 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)
1028 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: £862, Upfront: £10,173, Break-even: 11.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2056 kWh 822 kWh 1233 kWh £221 £123 £345 £4,069 11.8 yrs £2,825
3 kW 3084 kWh 1233 kWh 1850 kWh £332 £185 £517 £6,104 11.8 yrs £4,237
4 kW 4111 kWh 1645 kWh 2467 kWh £443 £247 £689 £8,138 11.8 yrs £5,650
5 kW 5139 kWh 2056 kWh 3084 kWh £553 £308 £862 £10,173 11.8 yrs £7,062
6 kW 6167 kWh 2467 kWh 3700 kWh £664 £370 £1,034 £12,207 11.8 yrs £8,475
7 kW 7195 kWh 2878 kWh 4317 kWh £775 £432 £1,206 £14,242 11.8 yrs £9,887
8 kW 8223 kWh 3289 kWh 4934 kWh £885 £493 £1,379 £16,276 11.8 yrs £11,300

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: £1,036, 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 2056 kWh 1233 kWh 822 kWh £332 £82 £414 £6,169 14.9 yrs £2,116
3 kW 3084 kWh 1850 kWh 1233 kWh £498 £123 £621 £8,204 13.2 yrs £4,224
4 kW 4111 kWh 2467 kWh 1645 kWh £664 £164 £829 £10,238 12.4 yrs £6,332
5 kW 5139 kWh 3084 kWh 2056 kWh £830 £206 £1,036 £12,273 11.9 yrs £8,440
6 kW 6167 kWh 3700 kWh 2467 kWh £996 £247 £1,243 £14,307 11.5 yrs £10,549
7 kW 7195 kWh 4317 kWh 2878 kWh £1,162 £288 £1,450 £16,342 11.3 yrs £12,657
8 kW 8223 kWh 4934 kWh 3289 kWh £1,328 £329 £1,657 £18,376 11.1 yrs £14,765

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: £1,123, 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 2056 kWh 1439 kWh 617 kWh £387 £62 £449 £7,569 16.9 yrs £1,412
3 kW 3084 kWh 2158 kWh 925 kWh £581 £93 £674 £9,604 14.3 yrs £3,868
4 kW 4111 kWh 2878 kWh 1233 kWh £775 £123 £898 £11,638 13.0 yrs £6,324
5 kW 5139 kWh 3597 kWh 1542 kWh £968 £154 £1,123 £13,673 12.2 yrs £8,780
6 kW 6167 kWh 4317 kWh 1850 kWh £1,162 £185 £1,347 £15,707 11.7 yrs £11,236
7 kW 7195 kWh 5036 kWh 2158 kWh £1,356 £216 £1,572 £17,742 11.3 yrs £13,691
8 kW 8223 kWh 5756 kWh 2467 kWh £1,549 £247 £1,796 £19,776 11.0 yrs £16,147

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: £1,149, Upfront: £15,423, 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 2056 kWh 1501 kWh 555 kWh £404 £56 £459 £9,319 20.3 yrs £-129
3 kW 3084 kWh 2251 kWh 833 kWh £606 £83 £689 £11,354 16.5 yrs £2,431
4 kW 4111 kWh 3001 kWh 1110 kWh £808 £111 £919 £13,388 14.6 yrs £4,991
5 kW 5139 kWh 3752 kWh 1388 kWh £1,010 £139 £1,149 £15,423 13.4 yrs £7,551
6 kW 6167 kWh 4502 kWh 1665 kWh £1,212 £167 £1,378 £17,457 12.7 yrs £10,112
7 kW 7195 kWh 5252 kWh 1943 kWh £1,414 £194 £1,608 £19,492 12.1 yrs £12,672
8 kW 8223 kWh 6003 kWh 2220 kWh £1,616 £222 £1,838 £21,526 11.7 yrs £15,232

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: £1,166, Upfront: £17,173, Break-even: 14.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2056 kWh 1542 kWh 514 kWh £415 £51 £466 £11,069 23.7 yrs £-1,740
3 kW 3084 kWh 2313 kWh 771 kWh £623 £77 £700 £13,104 18.7 yrs £889
4 kW 4111 kWh 3084 kWh 1028 kWh £830 £103 £933 £15,138 16.2 yrs £3,519
5 kW 5139 kWh 3854 kWh 1285 kWh £1,038 £128 £1,166 £17,173 14.7 yrs £6,149
6 kW 6167 kWh 4625 kWh 1542 kWh £1,245 £154 £1,399 £19,207 13.7 yrs £8,779
7 kW 7195 kWh 5396 kWh 1799 kWh £1,453 £180 £1,633 £21,242 13.0 yrs £11,409
8 kW 8223 kWh 6167 kWh 2056 kWh £1,660 £206 £1,866 £23,276 12.5 yrs £14,039

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: £1,183, Upfront: £19,623, Break-even: 16.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2056 kWh 1583 kWh 473 kWh £426 £47 £473 £13,519 28.6 yrs £-4,051
3 kW 3084 kWh 2374 kWh 709 kWh £639 £71 £710 £15,554 21.9 yrs £-1,352
4 kW 4111 kWh 3166 kWh 946 kWh £852 £95 £947 £17,588 18.6 yrs £1,348
5 kW 5139 kWh 3957 kWh 1182 kWh £1,065 £118 £1,183 £19,623 16.6 yrs £4,047
6 kW 6167 kWh 4749 kWh 1418 kWh £1,278 £142 £1,420 £21,657 15.2 yrs £6,746
7 kW 7195 kWh 5540 kWh 1655 kWh £1,491 £165 £1,657 £23,692 14.3 yrs £9,446
8 kW 8223 kWh 6331 kWh 1891 kWh £1,704 £189 £1,894 £25,726 13.6 yrs £12,145

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 TN9

Figures below are tailored to TN9 — click through for full league tables.

Big-Roof Britain Rank #1962 of 2182
4.2 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #374 of 2997
10.3 years (UK avg 11.3 years)
~£992 /yr • £10,173 upfront
Standing-Charge Drag Rank #877 of 2997
17.5% (UK avg 21.7%) drag on savings
£174 fixed • ~£992 /yr value

Your Area at a Glance

Your Electricity Rate
26.92p/kWh
Daily Fixed Charge
47.60p/day
Local Sunshine
1028kWh/kW
A 1 kW system generates ~1028 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: 58% • Flats: 38% • Bungalows: 2% Based on 5,284 properties

Coverage

Tonbridge and Malling (100%)

Areas Covered

Cage Green & Angel, Judd, Vauxhall

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

TN11 (Tonbridge and Malling)
≈2.2 km away
Local sunshine: ~1,042 kWh/kWp · +1% vs TN9
TN10 (Tonbridge and Malling)
≈2.4 km away
Local sunshine: ~1,034 kWh/kWp · +1% vs TN9
TN4 (Tunbridge Wells)
≈5.0 km away
Local sunshine: ~1,028 kWh/kWp · -0% vs TN9
TN2 (Tunbridge Wells)
≈5.3 km away
Local sunshine: ~1,029 kWh/kWp · +0% vs TN9
TN1 (Tunbridge Wells)
≈6.3 km away
Local sunshine: ~1,029 kWh/kWp · +0% vs TN9
TN3 (Tunbridge Wells)
≈7.9 km away
Local sunshine: ~1,023 kWh/kWp · -0% vs TN9

Similar sunshine across the UK

NR28 (North Norfolk)
~1,028 kWh/kWp · +0% vs TN9
TA8 (Somerset)
~1,028 kWh/kWp · +0% vs TN9
TA9 (Somerset)
~1,028 kWh/kWp · +0% vs TN9