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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SA20 (Carmarthenshire)

See if solar pays off for you in Carmarthenshire — 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
14.1 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£867
What you save every year
Profit Over 25 Years
£9,462
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 Wales, the current unit rate is 26.83p/kWh with a 51.69p/day standing charge. Your postcode’s south-facing sunshine yield is 863 kWh/kW — 105 below the regional median (968).

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 863 kWh per year on a south-facing roof. We value self-used electricity at 26.8p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.8p/kWh
Standing charge
51.7p/day
Sunshine yield (south)
863 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: £722, Upfront: £10,173, 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 1727 kWh 691 kWh 1036 kWh £185 £104 £289 £4,069 14.1 yrs £1,709
3 kW 2590 kWh 1036 kWh 1554 kWh £278 £155 £433 £6,104 14.1 yrs £2,564
4 kW 3454 kWh 1381 kWh 2072 kWh £371 £207 £578 £8,138 14.1 yrs £3,419
5 kW 4317 kWh 1727 kWh 2590 kWh £463 £259 £722 £10,173 14.1 yrs £4,274
6 kW 5180 kWh 2072 kWh 3108 kWh £556 £311 £867 £12,207 14.1 yrs £5,128
7 kW 6044 kWh 2417 kWh 3626 kWh £649 £363 £1,011 £14,242 14.1 yrs £5,983
8 kW 6907 kWh 2763 kWh 4144 kWh £741 £414 £1,156 £16,276 14.1 yrs £6,838

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: £868, Upfront: £12,273, 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 1727 kWh 1036 kWh 691 kWh £278 £69 £347 £6,169 17.8 yrs £772
3 kW 2590 kWh 1554 kWh 1036 kWh £417 £104 £521 £8,204 15.8 yrs £2,208
4 kW 3454 kWh 2072 kWh 1381 kWh £556 £138 £694 £10,238 14.8 yrs £3,644
5 kW 4317 kWh 2590 kWh 1727 kWh £695 £173 £868 £12,273 14.1 yrs £5,080
6 kW 5180 kWh 3108 kWh 2072 kWh £834 £207 £1,041 £14,307 13.7 yrs £6,516
7 kW 6044 kWh 3626 kWh 2417 kWh £973 £242 £1,215 £16,342 13.5 yrs £7,952
8 kW 6907 kWh 4144 kWh 2763 kWh £1,112 £276 £1,388 £18,376 13.2 yrs £9,387

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: £940, Upfront: £13,673, 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 1727 kWh 1209 kWh 518 kWh £324 £52 £376 £7,569 20.1 yrs £-47
3 kW 2590 kWh 1813 kWh 777 kWh £486 £78 £564 £9,604 17.0 yrs £1,680
4 kW 3454 kWh 2417 kWh 1036 kWh £649 £104 £752 £11,638 15.5 yrs £3,406
5 kW 4317 kWh 3022 kWh 1295 kWh £811 £130 £940 £13,673 14.5 yrs £5,133
6 kW 5180 kWh 3626 kWh 1554 kWh £973 £155 £1,128 £15,707 13.9 yrs £6,859
7 kW 6044 kWh 4231 kWh 1813 kWh £1,135 £181 £1,316 £17,742 13.5 yrs £8,586
8 kW 6907 kWh 4835 kWh 2072 kWh £1,297 £207 £1,504 £19,776 13.1 yrs £10,312

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: £962, Upfront: £15,423, 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 1727 kWh 1261 kWh 466 kWh £338 £47 £385 £9,319 24.2 yrs £-1,623
3 kW 2590 kWh 1891 kWh 699 kWh £507 £70 £577 £11,354 19.7 yrs £191
4 kW 3454 kWh 2521 kWh 932 kWh £676 £93 £770 £13,388 17.4 yrs £2,005
5 kW 4317 kWh 3151 kWh 1166 kWh £846 £117 £962 £15,423 16.0 yrs £3,819
6 kW 5180 kWh 3782 kWh 1399 kWh £1,015 £140 £1,154 £17,457 15.1 yrs £5,632
7 kW 6044 kWh 4412 kWh 1632 kWh £1,184 £163 £1,347 £19,492 14.5 yrs £7,446
8 kW 6907 kWh 5042 kWh 1865 kWh £1,353 £186 £1,539 £21,526 14.0 yrs £9,260

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: £977, Upfront: £17,173, Break-even: 17.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1727 kWh 1295 kWh 432 kWh £347 £43 £391 £11,069 28.3 yrs £-3,256
3 kW 2590 kWh 1943 kWh 648 kWh £521 £65 £586 £13,104 22.4 yrs £-1,384
4 kW 3454 kWh 2590 kWh 863 kWh £695 £86 £781 £15,138 19.4 yrs £487
5 kW 4317 kWh 3238 kWh 1079 kWh £869 £108 £977 £17,173 17.6 yrs £2,359
6 kW 5180 kWh 3885 kWh 1295 kWh £1,042 £130 £1,172 £19,207 16.4 yrs £4,231
7 kW 6044 kWh 4533 kWh 1511 kWh £1,216 £151 £1,367 £21,242 15.5 yrs £6,103
8 kW 6907 kWh 5180 kWh 1727 kWh £1,390 £173 £1,563 £23,276 14.9 yrs £7,975

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: £991, Upfront: £19,623, Break-even: 19.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1727 kWh 1330 kWh 397 kWh £357 £40 £396 £13,519 34.1 yrs £-5,590
3 kW 2590 kWh 1994 kWh 596 kWh £535 £60 £595 £15,554 26.2 yrs £-3,660
4 kW 3454 kWh 2659 kWh 794 kWh £713 £79 £793 £17,588 22.2 yrs £-1,730
5 kW 4317 kWh 3324 kWh 993 kWh £892 £99 £991 £19,623 19.8 yrs £200
6 kW 5180 kWh 3989 kWh 1191 kWh £1,070 £119 £1,189 £21,657 18.2 yrs £2,130
7 kW 6044 kWh 4654 kWh 1390 kWh £1,249 £139 £1,388 £23,692 17.1 yrs £4,060
8 kW 6907 kWh 5318 kWh 1589 kWh £1,427 £159 £1,586 £25,726 16.2 yrs £5,990

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 SA20

Figures below are tailored to SA20 — click through for full league tables.

Big-Roof Britain Rank #69 of 2182
6.8 kWp (UK avg 5.1 kWp)
~14 panels (≈430 W)
Solar Payback Index Rank #2524 of 2997
12.2 years (UK avg 11.3 years)
~£998 /yr • £12,207 upfront
Standing-Charge Drag Rank #1221 of 2997
18.9% (UK avg 21.7%) drag on savings
£189 fixed • ~£998 /yr value

Your Area at a Glance

Your Electricity Rate
26.83p/kWh
Daily Fixed Charge
51.69p/day
Local Sunshine
863kWh/kW
A 1 kW system generates ~863 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: 72% • Flats: 6% • Bungalows: 21% Based on 869 properties

Coverage

Carmarthenshire (100%)

Areas Covered

Llandovery, Cilycwm, Llangadog, Manordeilo and Salem

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 Wales

SA19 (Carmarthenshire)
≈14.1 km away
Local sunshine: ~894 kWh/kWp · +4% vs SA20
LD5 (Powys)
≈17.3 km away
Local sunshine: ~878 kWh/kWp · +2% vs SA20
LD4 (Powys)
≈21.1 km away
Local sunshine: ~903 kWh/kWp · +5% vs SA20
SA48 (Ceredigion)
≈24.1 km away
Local sunshine: ~888 kWh/kWp · +3% vs SA20
SA9 (Powys)
≈24.3 km away
Local sunshine: ~873 kWh/kWp · +1% vs SA20
SA18 (Carmarthenshire)
≈25.9 km away
Local sunshine: ~895 kWh/kWp · +4% vs SA20

Similar sunshine across the UK

BT69 (Mid Ulster)
~863 kWh/kWp · +0% vs SA20
DG14 (Dumfries and Galloway)
~863 kWh/kWp · -0% vs SA20
LL42 (Gwynedd)
~864 kWh/kWp · +0% vs SA20