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

Solar Panels in NN1 (West Northamptonshire)

See if solar pays off for you in West Northamptonshire — 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
12.7 years
After this, it's pure profit
Upfront Cost
£6,104
What you pay to get started
Annual Benefit
£482
What you save every year
Profit Over 25 Years
£5,942
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 3.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 990 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
49.1p/day
Sunshine yield (south)
990 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: £803, Upfront: £10,173, Break-even: 12.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1980 kWh 792 kWh 1188 kWh £202 £119 £321 £4,069 12.7 yrs £2,355
3 kW 2971 kWh 1188 kWh 1782 kWh £304 £178 £482 £6,104 12.7 yrs £3,533
4 kW 3961 kWh 1584 kWh 2376 kWh £405 £238 £642 £8,138 12.7 yrs £4,711
5 kW 4951 kWh 1980 kWh 2971 kWh £506 £297 £803 £10,173 12.7 yrs £5,888
6 kW 5941 kWh 2376 kWh 3565 kWh £607 £356 £964 £12,207 12.7 yrs £7,066
7 kW 6931 kWh 2773 kWh 4159 kWh £708 £416 £1,124 £14,242 12.7 yrs £8,243
8 kW 7921 kWh 3169 kWh 4753 kWh £810 £475 £1,285 £16,276 12.7 yrs £9,421

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: £957, Upfront: £12,273, 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 1980 kWh 1188 kWh 792 kWh £304 £79 £383 £6,169 16.1 yrs £1,487
3 kW 2971 kWh 1782 kWh 1188 kWh £455 £119 £574 £8,204 14.3 yrs £3,281
4 kW 3961 kWh 2376 kWh 1584 kWh £607 £158 £766 £10,238 13.4 yrs £5,074
5 kW 4951 kWh 2971 kWh 1980 kWh £759 £198 £957 £12,273 12.8 yrs £6,868
6 kW 5941 kWh 3565 kWh 2376 kWh £911 £238 £1,148 £14,307 12.5 yrs £8,661
7 kW 6931 kWh 4159 kWh 2773 kWh £1,063 £277 £1,340 £16,342 12.2 yrs £10,455
8 kW 7921 kWh 4753 kWh 3169 kWh £1,214 £317 £1,531 £18,376 12.0 yrs £12,248

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: £1,034, Upfront: £13,673, 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 1980 kWh 1386 kWh 594 kWh £354 £59 £414 £7,569 18.3 yrs £703
3 kW 2971 kWh 2079 kWh 891 kWh £531 £89 £620 £9,604 15.5 yrs £2,804
4 kW 3961 kWh 2773 kWh 1188 kWh £708 £119 £827 £11,638 14.1 yrs £4,906
5 kW 4951 kWh 3466 kWh 1485 kWh £885 £149 £1,034 £13,673 13.2 yrs £7,007
6 kW 5941 kWh 4159 kWh 1782 kWh £1,063 £178 £1,241 £15,707 12.7 yrs £9,109
7 kW 6931 kWh 4852 kWh 2079 kWh £1,240 £208 £1,448 £17,742 12.3 yrs £11,210
8 kW 7921 kWh 5545 kWh 2376 kWh £1,417 £238 £1,654 £19,776 12.0 yrs £13,312

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: £1,057, Upfront: £15,423, Break-even: 14.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1980 kWh 1446 kWh 535 kWh £369 £53 £423 £9,319 22.0 yrs £-862
3 kW 2971 kWh 2168 kWh 802 kWh £554 £80 £634 £11,354 17.9 yrs £1,332
4 kW 3961 kWh 2891 kWh 1069 kWh £739 £107 £846 £13,388 15.8 yrs £3,525
5 kW 4951 kWh 3614 kWh 1337 kWh £923 £134 £1,057 £15,423 14.6 yrs £5,719
6 kW 5941 kWh 4337 kWh 1604 kWh £1,108 £160 £1,269 £17,457 13.8 yrs £7,913
7 kW 6931 kWh 5060 kWh 1871 kWh £1,293 £187 £1,480 £19,492 13.2 yrs £10,107
8 kW 7921 kWh 5783 kWh 2139 kWh £1,477 £214 £1,691 £21,526 12.7 yrs £12,301

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: £1,072, Upfront: £17,173, Break-even: 16.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1980 kWh 1485 kWh 495 kWh £379 £50 £429 £11,069 25.8 yrs £-2,489
3 kW 2971 kWh 2228 kWh 743 kWh £569 £74 £643 £13,104 20.4 yrs £-234
4 kW 3961 kWh 2971 kWh 990 kWh £759 £99 £858 £15,138 17.6 yrs £2,022
5 kW 4951 kWh 3713 kWh 1238 kWh £949 £124 £1,072 £17,173 16.0 yrs £4,277
6 kW 5941 kWh 4456 kWh 1485 kWh £1,138 £149 £1,287 £19,207 14.9 yrs £6,533
7 kW 6931 kWh 5198 kWh 1733 kWh £1,328 £173 £1,501 £21,242 14.1 yrs £8,788
8 kW 7921 kWh 5941 kWh 1980 kWh £1,518 £198 £1,716 £23,276 13.6 yrs £11,044

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: £1,088, Upfront: £19,623, Break-even: 18.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1980 kWh 1525 kWh 455 kWh £390 £46 £435 £13,519 31.1 yrs £-4,816
3 kW 2971 kWh 2287 kWh 683 kWh £584 £68 £653 £15,554 23.8 yrs £-2,499
4 kW 3961 kWh 3050 kWh 911 kWh £779 £91 £870 £17,588 20.2 yrs £-182
5 kW 4951 kWh 3812 kWh 1139 kWh £974 £114 £1,088 £19,623 18.0 yrs £2,135
6 kW 5941 kWh 4575 kWh 1366 kWh £1,169 £137 £1,305 £21,657 16.6 yrs £4,452
7 kW 6931 kWh 5337 kWh 1594 kWh £1,364 £159 £1,523 £23,692 15.6 yrs £6,769
8 kW 7921 kWh 6100 kWh 1822 kWh £1,558 £182 £1,741 £25,726 14.8 yrs £9,086

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
25.55p/kWh
Daily Fixed Charge
49.09p/day
Local Sunshine
990kWh/kW
A 1 kW system generates ~990 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
3.0kW
For houses & bungalows in this area

⚠️ This area is predominantly flats. Many residents require freeholder approval for solar installations. System size shown reflects houses and bungalows only.

Local Property Data

Property Types

Houses: 42% • Flats: 54% • Bungalows: 1% Based on 13,196 properties

Coverage

West Northamptonshire (100%)

Areas Covered

Castle, Kingsley & Semilong, Abington & Phippsville, Dallington Spencer, Weston Favell & Abington Vale, Far Cotton, Delapre & Briar Hill, Headlands

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.