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

Solar Panels in DA18 (Bexley)

See if solar pays off for you in Bexley — 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
12.3 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£826
What you save every year
Profit Over 25 Years
£10,480
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 1017 kWh per year on a south-facing roof. We value self-used electricity at 25.6p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
25.6p/kWh
Standing charge
46.1p/day
Sunshine yield (south)
1017 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: £826, Upfront: £10,173, 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 2033 kWh 813 kWh 1220 kWh £208 £122 £330 £4,069 12.3 yrs £2,540
3 kW 3050 kWh 1220 kWh 1830 kWh £313 £183 £496 £6,104 12.3 yrs £3,810
4 kW 4067 kWh 1627 kWh 2440 kWh £417 £244 £661 £8,138 12.3 yrs £5,080
5 kW 5083 kWh 2033 kWh 3050 kWh £521 £305 £826 £10,173 12.3 yrs £6,350
6 kW 6100 kWh 2440 kWh 3660 kWh £625 £366 £991 £12,207 12.3 yrs £7,620
7 kW 7116 kWh 2847 kWh 4270 kWh £730 £427 £1,157 £14,242 12.3 yrs £8,890
8 kW 8133 kWh 3253 kWh 4880 kWh £834 £488 £1,322 £16,276 12.3 yrs £10,160

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: £985, Upfront: £12,273, Break-even: 12.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2033 kWh 1220 kWh 813 kWh £313 £81 £394 £6,169 15.7 yrs £1,711
3 kW 3050 kWh 1830 kWh 1220 kWh £469 £122 £591 £8,204 13.9 yrs £3,617
4 kW 4067 kWh 2440 kWh 1627 kWh £625 £163 £788 £10,238 13.0 yrs £5,522
5 kW 5083 kWh 3050 kWh 2033 kWh £782 £203 £985 £12,273 12.5 yrs £7,428
6 kW 6100 kWh 3660 kWh 2440 kWh £938 £244 £1,182 £14,307 12.1 yrs £9,333
7 kW 7116 kWh 4270 kWh 2847 kWh £1,094 £285 £1,379 £16,342 11.9 yrs £11,239
8 kW 8133 kWh 4880 kWh 3253 kWh £1,251 £325 £1,576 £18,376 11.7 yrs £13,144

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: £1,064, Upfront: £13,673, Break-even: 12.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2033 kWh 1423 kWh 610 kWh £365 £61 £426 £7,569 17.8 yrs £947
3 kW 3050 kWh 2135 kWh 915 kWh £547 £91 £639 £9,604 15.0 yrs £3,170
4 kW 4067 kWh 2847 kWh 1220 kWh £730 £122 £852 £11,638 13.7 yrs £5,393
5 kW 5083 kWh 3558 kWh 1525 kWh £912 £152 £1,064 £13,673 12.8 yrs £7,617
6 kW 6100 kWh 4270 kWh 1830 kWh £1,094 £183 £1,277 £15,707 12.3 yrs £9,840
7 kW 7116 kWh 4981 kWh 2135 kWh £1,277 £213 £1,490 £17,742 11.9 yrs £12,063
8 kW 8133 kWh 5693 kWh 2440 kWh £1,459 £244 £1,703 £19,776 11.6 yrs £14,287

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: £1,088, Upfront: £15,423, Break-even: 14.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2033 kWh 1484 kWh 549 kWh £380 £55 £435 £9,319 21.4 yrs £-613
3 kW 3050 kWh 2226 kWh 823 kWh £571 £82 £653 £11,354 17.4 yrs £1,706
4 kW 4067 kWh 2969 kWh 1098 kWh £761 £110 £871 £13,388 15.4 yrs £4,025
5 kW 5083 kWh 3711 kWh 1372 kWh £951 £137 £1,088 £15,423 14.2 yrs £6,343
6 kW 6100 kWh 4453 kWh 1647 kWh £1,141 £165 £1,306 £17,457 13.4 yrs £8,662
7 kW 7116 kWh 5195 kWh 1921 kWh £1,331 £192 £1,524 £19,492 12.8 yrs £10,981
8 kW 8133 kWh 5937 kWh 2196 kWh £1,522 £220 £1,741 £21,526 12.4 yrs £13,299

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: £1,104, Upfront: £17,173, Break-even: 15.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2033 kWh 1525 kWh 508 kWh £391 £51 £442 £11,069 25.1 yrs £-2,236
3 kW 3050 kWh 2287 kWh 762 kWh £586 £76 £663 £13,104 19.8 yrs £147
4 kW 4067 kWh 3050 kWh 1017 kWh £782 £102 £883 £15,138 17.1 yrs £2,529
5 kW 5083 kWh 3812 kWh 1271 kWh £977 £127 £1,104 £17,173 15.6 yrs £4,911
6 kW 6100 kWh 4575 kWh 1525 kWh £1,173 £152 £1,325 £19,207 14.5 yrs £7,293
7 kW 7116 kWh 5337 kWh 1779 kWh £1,368 £178 £1,546 £21,242 13.7 yrs £9,676
8 kW 8133 kWh 6100 kWh 2033 kWh £1,563 £203 £1,767 £23,276 13.2 yrs £12,058

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: £1,120, Upfront: £19,623, Break-even: 17.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2033 kWh 1566 kWh 468 kWh £401 £47 £448 £13,519 30.2 yrs £-4,558
3 kW 3050 kWh 2348 kWh 701 kWh £602 £70 £672 £15,554 23.1 yrs £-2,113
4 kW 4067 kWh 3131 kWh 935 kWh £803 £94 £896 £17,588 19.6 yrs £333
5 kW 5083 kWh 3914 kWh 1169 kWh £1,003 £117 £1,120 £19,623 17.5 yrs £2,779
6 kW 6100 kWh 4697 kWh 1403 kWh £1,204 £140 £1,344 £21,657 16.1 yrs £5,225
7 kW 7116 kWh 5480 kWh 1637 kWh £1,404 £164 £1,568 £23,692 15.1 yrs £7,671
8 kW 8133 kWh 6262 kWh 1871 kWh £1,605 £187 £1,792 £25,726 14.4 yrs £10,116

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
25.63p/kWh
Daily Fixed Charge
46.06p/day
Local Sunshine
1017kWh/kW
A 1 kW system generates ~1017 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: 43% • Flats: 49% • Bungalows: 0% Based on 801 properties

Coverage

Bexley (100%)

Areas Covered

Thamesmead East, Slade Green & Northend

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.