Solar explained to clever people by people who are not trying to be clever

Solar Panels in DA9 (Dartford)

See if solar pays off for you in Dartford — 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
£859
What you save every year
Profit Over 25 Years
£11,306
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

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 1025 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)
1025 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: £859, 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 2050 kWh 820 kWh 1230 kWh £221 £123 £344 £4,069 11.8 yrs £2,804
3 kW 3074 kWh 1230 kWh 1845 kWh £331 £184 £515 £6,104 11.8 yrs £4,206
4 kW 4099 kWh 1640 kWh 2459 kWh £441 £246 £687 £8,138 11.8 yrs £5,609
5 kW 5124 kWh 2050 kWh 3074 kWh £552 £307 £859 £10,173 11.8 yrs £7,011
6 kW 6149 kWh 2459 kWh 3689 kWh £662 £369 £1,031 £12,207 11.8 yrs £8,413
7 kW 7173 kWh 2869 kWh 4304 kWh £772 £430 £1,203 £14,242 11.8 yrs £9,815
8 kW 8198 kWh 3279 kWh 4919 kWh £883 £492 £1,375 £16,276 11.8 yrs £11,217

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: £1,033, 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 2050 kWh 1230 kWh 820 kWh £331 £82 £413 £6,169 14.9 yrs £2,091
3 kW 3074 kWh 1845 kWh 1230 kWh £497 £123 £620 £8,204 13.2 yrs £4,187
4 kW 4099 kWh 2459 kWh 1640 kWh £662 £164 £826 £10,238 12.4 yrs £6,283
5 kW 5124 kWh 3074 kWh 2050 kWh £828 £205 £1,033 £12,273 11.9 yrs £8,378
6 kW 6149 kWh 3689 kWh 2459 kWh £993 £246 £1,239 £14,307 11.5 yrs £10,474
7 kW 7173 kWh 4304 kWh 2869 kWh £1,159 £287 £1,446 £16,342 11.3 yrs £12,570
8 kW 8198 kWh 4919 kWh 3279 kWh £1,324 £328 £1,652 £18,376 11.1 yrs £14,665

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: £1,119, 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 2050 kWh 1435 kWh 615 kWh £386 £61 £448 £7,569 16.9 yrs £1,385
3 kW 3074 kWh 2152 kWh 922 kWh £579 £92 £672 £9,604 14.3 yrs £3,827
4 kW 4099 kWh 2869 kWh 1230 kWh £772 £123 £895 £11,638 13.0 yrs £6,270
5 kW 5124 kWh 3587 kWh 1537 kWh £966 £154 £1,119 £13,673 12.2 yrs £8,712
6 kW 6149 kWh 4304 kWh 1845 kWh £1,159 £184 £1,343 £15,707 11.7 yrs £11,155
7 kW 7173 kWh 5021 kWh 2152 kWh £1,352 £215 £1,567 £17,742 11.3 yrs £13,597
8 kW 8198 kWh 5739 kWh 2459 kWh £1,545 £246 £1,791 £19,776 11.0 yrs £16,040

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: £1,145, 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 2050 kWh 1496 kWh 553 kWh £403 £55 £458 £9,319 20.3 yrs £-157
3 kW 3074 kWh 2244 kWh 830 kWh £604 £83 £687 £11,354 16.5 yrs £2,389
4 kW 4099 kWh 2992 kWh 1107 kWh £806 £111 £916 £13,388 14.6 yrs £4,936
5 kW 5124 kWh 3740 kWh 1383 kWh £1,007 £138 £1,145 £15,423 13.5 yrs £7,482
6 kW 6149 kWh 4488 kWh 1660 kWh £1,208 £166 £1,374 £17,457 12.7 yrs £10,029
7 kW 7173 kWh 5237 kWh 1937 kWh £1,410 £194 £1,603 £19,492 12.2 yrs £12,575
8 kW 8198 kWh 5985 kWh 2213 kWh £1,611 £221 £1,832 £21,526 11.7 yrs £15,122

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: £1,163, 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 2050 kWh 1537 kWh 512 kWh £414 £51 £465 £11,069 23.8 yrs £-1,768
3 kW 3074 kWh 2306 kWh 769 kWh £621 £77 £698 £13,104 18.8 yrs £848
4 kW 4099 kWh 3074 kWh 1025 kWh £828 £102 £930 £15,138 16.3 yrs £3,463
5 kW 5124 kWh 3843 kWh 1281 kWh £1,034 £128 £1,163 £17,173 14.8 yrs £6,079
6 kW 6149 kWh 4611 kWh 1537 kWh £1,241 £154 £1,395 £19,207 13.8 yrs £8,695
7 kW 7173 kWh 5380 kWh 1793 kWh £1,448 £179 £1,628 £21,242 13.1 yrs £11,311
8 kW 8198 kWh 6149 kWh 2050 kWh £1,655 £205 £1,860 £23,276 12.5 yrs £13,927

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: £1,180, 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 2050 kWh 1578 kWh 471 kWh £425 £47 £472 £13,519 28.6 yrs £-4,080
3 kW 3074 kWh 2367 kWh 707 kWh £637 £71 £708 £15,554 22.0 yrs £-1,394
4 kW 4099 kWh 3156 kWh 943 kWh £850 £94 £944 £17,588 18.6 yrs £1,291
5 kW 5124 kWh 3945 kWh 1178 kWh £1,062 £118 £1,180 £19,623 16.6 yrs £3,976
6 kW 6149 kWh 4734 kWh 1414 kWh £1,274 £141 £1,416 £21,657 15.3 yrs £6,661
7 kW 7173 kWh 5523 kWh 1650 kWh £1,487 £165 £1,652 £23,692 14.3 yrs £9,346
8 kW 8198 kWh 6313 kWh 1886 kWh £1,699 £189 £1,888 £25,726 13.6 yrs £12,032

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.

Your Area at a Glance

Your Electricity Rate
26.92p/kWh
Daily Fixed Charge
47.60p/day
Local Sunshine
1025kWh/kW
A 1 kW system generates ~1025 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: 50% • Flats: 46% • Bungalows: 1% Based on 4,809 properties

Coverage

Dartford (100%)

Areas Covered

Stone Castle, Greenhithe & Knockhall, Swanscombe, West Hill, Ebbsfleet

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.