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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in LL42 (Gwynedd)

See if solar pays off for you in Gwynedd — 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
13.8 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£886
What you save every year
Profit Over 25 Years
£9,939
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 North Wales and Mersey, the current unit rate is 27.72p/kWh with a 69.95p/day standing charge. Your postcode’s south-facing sunshine yield is 864 kWh/kW — 66 below the regional median (930).

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 864 kWh per year on a south-facing roof. We value self-used electricity at 27.7p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
27.7p/kWh
Standing charge
70.0p/day
Sunshine yield (south)
864 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: £738, Upfront: £10,173, Break-even: 13.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1728 kWh 691 kWh 1037 kWh £192 £104 £295 £4,069 13.8 yrs £1,837
3 kW 2592 kWh 1037 kWh 1555 kWh £287 £156 £443 £6,104 13.8 yrs £2,755
4 kW 3456 kWh 1382 kWh 2074 kWh £383 £207 £591 £8,138 13.8 yrs £3,673
5 kW 4320 kWh 1728 kWh 2592 kWh £479 £259 £738 £10,173 13.8 yrs £4,591
6 kW 5184 kWh 2074 kWh 3110 kWh £575 £311 £886 £12,207 13.8 yrs £5,510
7 kW 6048 kWh 2419 kWh 3629 kWh £671 £363 £1,033 £14,242 13.8 yrs £6,428
8 kW 6912 kWh 2765 kWh 4147 kWh £766 £415 £1,181 £16,276 13.8 yrs £7,346

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: £891, Upfront: £12,273, Break-even: 13.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1728 kWh 1037 kWh 691 kWh £287 £69 £357 £6,169 17.3 yrs £961
3 kW 2592 kWh 1555 kWh 1037 kWh £431 £104 £535 £8,204 15.3 yrs £2,492
4 kW 3456 kWh 2074 kWh 1382 kWh £575 £138 £713 £10,238 14.4 yrs £4,023
5 kW 4320 kWh 2592 kWh 1728 kWh £719 £173 £891 £12,273 13.8 yrs £5,553
6 kW 5184 kWh 3110 kWh 2074 kWh £862 £207 £1,070 £14,307 13.4 yrs £7,084
7 kW 6048 kWh 3629 kWh 2419 kWh £1,006 £242 £1,248 £16,342 13.1 yrs £8,615
8 kW 6912 kWh 4147 kWh 2765 kWh £1,150 £276 £1,426 £18,376 12.9 yrs £10,146

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: £968, Upfront: £13,673, Break-even: 14.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1728 kWh 1210 kWh 518 kWh £335 £52 £387 £7,569 19.6 yrs £174
3 kW 2592 kWh 1814 kWh 778 kWh £503 £78 £581 £9,604 16.5 yrs £2,011
4 kW 3456 kWh 2419 kWh 1037 kWh £671 £104 £774 £11,638 15.0 yrs £3,848
5 kW 4320 kWh 3024 kWh 1296 kWh £838 £130 £968 £13,673 14.1 yrs £5,685
6 kW 5184 kWh 3629 kWh 1555 kWh £1,006 £156 £1,161 £15,707 13.5 yrs £7,521
7 kW 6048 kWh 4234 kWh 1814 kWh £1,174 £181 £1,355 £17,742 13.1 yrs £9,358
8 kW 6912 kWh 4838 kWh 2074 kWh £1,341 £207 £1,549 £19,776 12.8 yrs £11,195

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: £991, Upfront: £15,423, 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 1728 kWh 1261 kWh 467 kWh £350 £47 £396 £9,319 23.5 yrs £-1,392
3 kW 2592 kWh 1892 kWh 700 kWh £525 £70 £594 £11,354 19.1 yrs £536
4 kW 3456 kWh 2523 kWh 933 kWh £699 £93 £793 £13,388 16.9 yrs £2,465
5 kW 4320 kWh 3154 kWh 1166 kWh £874 £117 £991 £15,423 15.6 yrs £4,394
6 kW 5184 kWh 3784 kWh 1400 kWh £1,049 £140 £1,189 £17,457 14.7 yrs £6,323
7 kW 6048 kWh 4415 kWh 1633 kWh £1,224 £163 £1,387 £19,492 14.1 yrs £8,251
8 kW 6912 kWh 5046 kWh 1866 kWh £1,399 £187 £1,585 £21,526 13.6 yrs £10,180

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: £1,006, Upfront: £17,173, Break-even: 17.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1728 kWh 1296 kWh 432 kWh £359 £43 £402 £11,069 27.5 yrs £-3,020
3 kW 2592 kWh 1944 kWh 648 kWh £539 £65 £604 £13,104 21.7 yrs £-1,030
4 kW 3456 kWh 2592 kWh 864 kWh £719 £86 £805 £15,138 18.8 yrs £960
5 kW 4320 kWh 3240 kWh 1080 kWh £898 £108 £1,006 £17,173 17.1 yrs £2,950
6 kW 5184 kWh 3888 kWh 1296 kWh £1,078 £130 £1,207 £19,207 15.9 yrs £4,940
7 kW 6048 kWh 4536 kWh 1512 kWh £1,257 £151 £1,409 £21,242 15.1 yrs £6,930
8 kW 6912 kWh 5184 kWh 1728 kWh £1,437 £173 £1,610 £23,276 14.5 yrs £8,920

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: £1,021, Upfront: £19,623, Break-even: 19.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1728 kWh 1331 kWh 397 kWh £369 £40 £409 £13,519 33.1 yrs £-5,348
3 kW 2592 kWh 1996 kWh 596 kWh £553 £60 £613 £15,554 25.4 yrs £-3,296
4 kW 3456 kWh 2661 kWh 795 kWh £738 £79 £817 £17,588 21.5 yrs £-1,245
5 kW 4320 kWh 3326 kWh 994 kWh £922 £99 £1,021 £19,623 19.2 yrs £806
6 kW 5184 kWh 3992 kWh 1192 kWh £1,106 £119 £1,226 £21,657 17.7 yrs £2,857
7 kW 6048 kWh 4657 kWh 1391 kWh £1,291 £139 £1,430 £23,692 16.6 yrs £4,909
8 kW 6912 kWh 5322 kWh 1590 kWh £1,475 £159 £1,634 £25,726 15.7 yrs £6,960

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 LL42

Figures below are tailored to LL42 — click through for full league tables.

Big-Roof Britain Rank #717 of 2182
5.3 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #2213 of 2997
11.9 years (UK avg 11.3 years)
~£1,024 /yr • £12,207 upfront
Standing-Charge Drag Rank #2206 of 2997
24.9% (UK avg 21.7%) drag on savings
£255 fixed • ~£1,024 /yr value

Your Area at a Glance

Your Electricity Rate
27.72p/kWh
Daily Fixed Charge
69.95p/day
Local Sunshine
864kWh/kW
A 1 kW system generates ~864 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: 45% • Flats: 38% • Bungalows: 7% Based on 887 properties

Coverage

Gwynedd (100%)

Areas Covered

Abermaw, De Dolgellau, Brithdir and Llanfachreth/Ganllwyd/Llanelltyd, Dyffryn Ardudwy

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 North Wales and Mersey

LL38 (Gwynedd)
≈3.1 km away
Local sunshine: ~846 kWh/kWp · -2% vs LL42
LL39 (Gwynedd)
≈3.4 km away
Local sunshine: ~825 kWh/kWp · -5% vs LL42
LL43 (Gwynedd)
≈6.1 km away
Local sunshine: ~875 kWh/kWp · +1% vs LL42
LL37 (Gwynedd)
≈6.7 km away
Local sunshine: ~878 kWh/kWp · +2% vs LL42
LL44 (Gwynedd)
≈7.7 km away
Local sunshine: ~875 kWh/kWp · +1% vs LL42
LL45 (Gwynedd)
≈11.0 km away
Local sunshine: ~835 kWh/kWp · -3% vs LL42

Similar sunshine across the UK

PA60 (Argyll and Bute)
~864 kWh/kWp · +0% vs LL42
AB24 (Aberdeen City)
~864 kWh/kWp · +0% vs LL42
PH2 (Perth and Kinross)
~864 kWh/kWp · +0% vs LL42