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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in TN11 (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
11.6 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£1,048
What you save every year
Profit Over 25 Years
£13,991
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 1042 kWh/kW — 13 above 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 1042 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)
1042 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: £873, Upfront: £10,173, Break-even: 11.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 833 kWh 1250 kWh £224 £125 £349 £4,069 11.6 yrs £2,917
3 kW 3125 kWh 1250 kWh 1875 kWh £336 £187 £524 £6,104 11.6 yrs £4,376
4 kW 4166 kWh 1667 kWh 2500 kWh £449 £250 £699 £8,138 11.6 yrs £5,834
5 kW 5208 kWh 2083 kWh 3125 kWh £561 £312 £873 £10,173 11.6 yrs £7,293
6 kW 6250 kWh 2500 kWh 3750 kWh £673 £375 £1,048 £12,207 11.6 yrs £8,751
7 kW 7291 kWh 2916 kWh 4375 kWh £785 £437 £1,223 £14,242 11.6 yrs £10,210
8 kW 8333 kWh 3333 kWh 5000 kWh £897 £500 £1,397 £16,276 11.6 yrs £11,669

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: £1,050, Upfront: £12,273, Break-even: 11.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1250 kWh 833 kWh £336 £83 £420 £6,169 14.7 yrs £2,227
3 kW 3125 kWh 1875 kWh 1250 kWh £505 £125 £630 £8,204 13.0 yrs £4,391
4 kW 4166 kWh 2500 kWh 1667 kWh £673 £167 £840 £10,238 12.2 yrs £6,554
5 kW 5208 kWh 3125 kWh 2083 kWh £841 £208 £1,050 £12,273 11.7 yrs £8,718
6 kW 6250 kWh 3750 kWh 2500 kWh £1,009 £250 £1,259 £14,307 11.4 yrs £10,881
7 kW 7291 kWh 4375 kWh 2916 kWh £1,178 £292 £1,469 £16,342 11.1 yrs £13,045
8 kW 8333 kWh 5000 kWh 3333 kWh £1,346 £333 £1,679 £18,376 10.9 yrs £15,208

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: £1,138, Upfront: £13,673, Break-even: 12.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1458 kWh 625 kWh £393 £62 £455 £7,569 16.6 yrs £1,532
3 kW 3125 kWh 2187 kWh 937 kWh £589 £94 £683 £9,604 14.1 yrs £4,048
4 kW 4166 kWh 2916 kWh 1250 kWh £785 £125 £910 £11,638 12.8 yrs £6,564
5 kW 5208 kWh 3646 kWh 1562 kWh £981 £156 £1,138 £13,673 12.0 yrs £9,080
6 kW 6250 kWh 4375 kWh 1875 kWh £1,178 £187 £1,365 £15,707 11.5 yrs £11,596
7 kW 7291 kWh 5104 kWh 2187 kWh £1,374 £219 £1,593 £17,742 11.1 yrs £14,112
8 kW 8333 kWh 5833 kWh 2500 kWh £1,570 £250 £1,820 £19,776 10.9 yrs £16,628

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: £1,164, Upfront: £15,423, Break-even: 13.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1521 kWh 562 kWh £409 £56 £466 £9,319 20.0 yrs £-7
3 kW 3125 kWh 2281 kWh 844 kWh £614 £84 £698 £11,354 16.3 yrs £2,615
4 kW 4166 kWh 3041 kWh 1125 kWh £819 £112 £931 £13,388 14.4 yrs £5,237
5 kW 5208 kWh 3802 kWh 1406 kWh £1,023 £141 £1,164 £15,423 13.2 yrs £7,859
6 kW 6250 kWh 4562 kWh 1687 kWh £1,228 £169 £1,397 £17,457 12.5 yrs £10,480
7 kW 7291 kWh 5323 kWh 1969 kWh £1,433 £197 £1,630 £19,492 12.0 yrs £13,102
8 kW 8333 kWh 6083 kWh 2250 kWh £1,638 £225 £1,862 £21,526 11.6 yrs £15,724

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: £1,182, Upfront: £17,173, Break-even: 14.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1562 kWh 521 kWh £421 £52 £473 £11,069 23.4 yrs £-1,616
3 kW 3125 kWh 2344 kWh 781 kWh £631 £78 £709 £13,104 18.5 yrs £1,077
4 kW 4166 kWh 3125 kWh 1042 kWh £841 £104 £945 £15,138 16.0 yrs £3,769
5 kW 5208 kWh 3906 kWh 1302 kWh £1,051 £130 £1,182 £17,173 14.5 yrs £6,461
6 kW 6250 kWh 4687 kWh 1562 kWh £1,262 £156 £1,418 £19,207 13.5 yrs £9,153
7 kW 7291 kWh 5468 kWh 1823 kWh £1,472 £182 £1,654 £21,242 12.8 yrs £11,846
8 kW 8333 kWh 6250 kWh 2083 kWh £1,682 £208 £1,891 £23,276 12.3 yrs £14,538

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: £1,199, Upfront: £19,623, Break-even: 16.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2083 kWh 1604 kWh 479 kWh £432 £48 £480 £13,519 28.2 yrs £-3,925
3 kW 3125 kWh 2406 kWh 719 kWh £648 £72 £720 £15,554 21.6 yrs £-1,162
4 kW 4166 kWh 3208 kWh 958 kWh £864 £96 £959 £17,588 18.3 yrs £1,601
5 kW 5208 kWh 4010 kWh 1198 kWh £1,080 £120 £1,199 £19,623 16.4 yrs £4,364
6 kW 6250 kWh 4812 kWh 1437 kWh £1,295 £144 £1,439 £21,657 15.0 yrs £7,126
7 kW 7291 kWh 5614 kWh 1677 kWh £1,511 £168 £1,679 £23,692 14.1 yrs £9,889
8 kW 8333 kWh 6416 kWh 1917 kWh £1,727 £192 £1,919 £25,726 13.4 yrs £12,652

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 TN11

Figures below are tailored to TN11 — click through for full league tables.

Big-Roof Britain Rank #281 of 2182
5.9 kWp (UK avg 5.1 kWp)
~12 panels (≈430 W)
Solar Payback Index Rank #245 of 2997
10.1 years (UK avg 11.3 years)
~£1,207 /yr • £12,207 upfront
Standing-Charge Drag Rank #175 of 2997
14.4% (UK avg 21.7%) drag on savings
£174 fixed • ~£1,207 /yr value

Your Area at a Glance

Your Electricity Rate
26.92p/kWh
Daily Fixed Charge
47.60p/day
Local Sunshine
1042kWh/kW
A 1 kW system generates ~1042 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: 75% • Flats: 12% • Bungalows: 12% Based on 3,507 properties

Coverage

Tonbridge and Malling (68%)|Sevenoaks (24%)|Tunbridge Wells (8%)

Areas Covered

Bourne, Hildenborough, Leigh and Chiddingstone Causeway, Cage Green & Angel, Penshurst, Fordcombe and Chiddingstone, Pembury & Capel, Vauxhall + 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

TN10 (Tonbridge and Malling)
≈0.7 km away
Local sunshine: ~1,034 kWh/kWp · -1% vs TN11
TN9 (Tonbridge and Malling)
≈2.2 km away
Local sunshine: ~1,028 kWh/kWp · -1% vs TN11
TN4 (Tunbridge Wells)
≈7.0 km away
Local sunshine: ~1,028 kWh/kWp · -1% vs TN11
TN2 (Tunbridge Wells)
≈7.4 km away
Local sunshine: ~1,029 kWh/kWp · -1% vs TN11
TN1 (Tunbridge Wells)
≈8.3 km away
Local sunshine: ~1,029 kWh/kWp · -1% vs TN11
TN13 (Sevenoaks)
≈8.9 km away
Local sunshine: ~1,015 kWh/kWp · -3% vs TN11

Similar sunshine across the UK

SS7 (Castle Point)
~1,042 kWh/kWp · -0% vs TN11
IP1 (Ipswich)
~1,042 kWh/kWp · +0% vs TN11
PL23 (Cornwall)
~1,041 kWh/kWp · -0% vs TN11