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Solar panel cost in Carmarthenshire (SA18)

See realistic solar installation costs, savings and payback for SA18 (Carmarthenshire) in under a minute using official UK data. Start with the calculator, then get a no-obligation quote from an MCS-certified installer. You can also ask the SolarByPostcode assistant to sanity-check your roof, bills and plans.

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
11.0 years
After this, it's pure profit
Upfront Cost
£8,139
What you pay to get started
Annual Benefit
£740
What you save every year
Profit Over 25 Years
£10,365
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: The official cost per kW is lower above 4 kW, so a 5–6 kW system can pay back a little faster than a 3–4 kW system on otherwise identical assumptions.
  • 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

Panel costs: Uses March 2026 TIC mean installation costs: £1,827/kW up to 4 kW and £1,628/kW above 4 kW.

Other costs: Battery prices are modelled at £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 26.33p/kWh with a 57.84p/day standing charge. Your postcode’s south-facing sunshine yield is 895 kWh/kW — 73 below the regional median (968).

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 895 kWh per year on a south-facing roof. We value self-used electricity at 26.3p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.3p/kWh
Standing charge
57.8p/day
Sunshine yield (south)
895 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: £740, Upfront: £8,139, Break-even: 11.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1791 kWh 716 kWh 1075 kWh £189 £107 £296 £3,256 11.0 yrs £2,666
3 kW 2686 kWh 1075 kWh 1612 kWh £283 £161 £444 £4,883 11.0 yrs £3,999
4 kW 3582 kWh 1433 kWh 2149 kWh £377 £215 £592 £6,511 11.0 yrs £5,332
5 kW 4477 kWh 1791 kWh 2686 kWh £472 £269 £740 £8,139 11.0 yrs £6,665
6 kW 5373 kWh 2149 kWh 3224 kWh £566 £322 £888 £9,767 11.0 yrs £7,998
7 kW 6268 kWh 2507 kWh 3761 kWh £660 £376 £1,036 £11,394 11.0 yrs £9,330
8 kW 7164 kWh 2865 kWh 4298 kWh £754 £430 £1,184 £13,022 11.0 yrs £10,663

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,628, battery £/kWh = 700.

3 kWh battery 5 kW example → Annual benefit: £886, Upfront: £10,239, Break-even: 11.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1791 kWh 1075 kWh 716 kWh £283 £72 £355 £5,356 15.1 yrs £1,736
3 kW 2686 kWh 1612 kWh 1075 kWh £424 £107 £532 £6,983 13.1 yrs £3,653
4 kW 3582 kWh 2149 kWh 1433 kWh £566 £143 £709 £8,611 12.1 yrs £5,571
5 kW 4477 kWh 2686 kWh 1791 kWh £707 £179 £886 £10,239 11.6 yrs £7,489
6 kW 5373 kWh 3224 kWh 2149 kWh £849 £215 £1,064 £11,867 11.2 yrs £9,407
7 kW 6268 kWh 3761 kWh 2507 kWh £990 £251 £1,241 £13,494 10.9 yrs £11,325
8 kW 7164 kWh 4298 kWh 2865 kWh £1,132 £287 £1,418 £15,122 10.7 yrs £13,243

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,628, battery £/kWh = 700.

5 kWh battery 5 kW example → Annual benefit: £960, Upfront: £11,639, Break-even: 12.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1791 kWh 1254 kWh 537 kWh £330 £54 £384 £6,756 17.6 yrs £921
3 kW 2686 kWh 1880 kWh 806 kWh £495 £81 £576 £8,383 14.6 yrs £3,131
4 kW 3582 kWh 2507 kWh 1075 kWh £660 £107 £768 £10,011 13.0 yrs £5,341
5 kW 4477 kWh 3134 kWh 1343 kWh £825 £134 £960 £11,639 12.1 yrs £7,551
6 kW 5373 kWh 3761 kWh 1612 kWh £990 £161 £1,151 £13,267 11.5 yrs £9,762
7 kW 6268 kWh 4388 kWh 1880 kWh £1,155 £188 £1,343 £14,894 11.1 yrs £11,972
8 kW 7164 kWh 5014 kWh 2149 kWh £1,320 £215 £1,535 £16,522 10.8 yrs £14,182

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,628, battery £/kWh = 700.

7.5 kWh battery 5 kW example → Annual benefit: £981, Upfront: £13,389, Break-even: 13.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1791 kWh 1307 kWh 484 kWh £344 £48 £393 £8,506 21.7 yrs £-654
3 kW 2686 kWh 1961 kWh 725 kWh £516 £73 £589 £10,133 17.2 yrs £1,644
4 kW 3582 kWh 2615 kWh 967 kWh £688 £97 £785 £11,761 15.0 yrs £3,942
5 kW 4477 kWh 3268 kWh 1209 kWh £861 £121 £981 £13,389 13.6 yrs £6,240
6 kW 5373 kWh 3922 kWh 1451 kWh £1,033 £145 £1,178 £15,017 12.8 yrs £8,538
7 kW 6268 kWh 4576 kWh 1692 kWh £1,205 £169 £1,374 £16,644 12.1 yrs £10,836
8 kW 7164 kWh 5229 kWh 1934 kWh £1,377 £193 £1,570 £18,272 11.6 yrs £13,134

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,628, battery £/kWh = 700.

10 kWh battery 5 kW example → Annual benefit: £996, Upfront: £15,139, Break-even: 15.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1791 kWh 1343 kWh 448 kWh £354 £45 £398 £10,256 25.7 yrs £-2,287
3 kW 2686 kWh 2015 kWh 672 kWh £530 £67 £598 £11,883 19.9 yrs £70
4 kW 3582 kWh 2686 kWh 895 kWh £707 £90 £797 £13,511 17.0 yrs £2,426
5 kW 4477 kWh 3358 kWh 1119 kWh £884 £112 £996 £15,139 15.2 yrs £4,783
6 kW 5373 kWh 4029 kWh 1343 kWh £1,061 £134 £1,195 £16,767 14.0 yrs £7,139
7 kW 6268 kWh 4701 kWh 1567 kWh £1,238 £157 £1,394 £18,394 13.2 yrs £9,496
8 kW 7164 kWh 5373 kWh 1791 kWh £1,415 £179 £1,594 £20,022 12.6 yrs £11,852

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,628, battery £/kWh = 700.

13.5 kWh battery 5 kW example → Annual benefit: £1,011, Upfront: £17,589, Break-even: 17.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1791 kWh 1379 kWh 412 kWh £363 £41 £404 £12,706 31.4 yrs £-4,620
3 kW 2686 kWh 2068 kWh 618 kWh £545 £62 £606 £14,333 23.6 yrs £-2,205
4 kW 3582 kWh 2758 kWh 824 kWh £726 £82 £809 £15,961 19.7 yrs £210
5 kW 4477 kWh 3447 kWh 1030 kWh £908 £103 £1,011 £17,589 17.4 yrs £2,625
6 kW 5373 kWh 4137 kWh 1236 kWh £1,089 £124 £1,213 £19,217 15.8 yrs £5,040
7 kW 6268 kWh 4826 kWh 1442 kWh £1,271 £144 £1,415 £20,844 14.7 yrs £7,455
8 kW 7164 kWh 5516 kWh 1648 kWh £1,452 £165 £1,617 £22,472 13.9 yrs £9,870

Assumptions: south-facing, sensible tilt; self-use shares from site rules; export at 10p baseline. Costs: panels £/kW = 1,628, 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.

Before you request quotes in Carmarthenshire

Use the numbers above to sanity-check installer quotes. The main things to compare are system size, battery assumptions, payback claims, MCS certification, DNO paperwork and export assumptions.

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Understand DNO, G98 and G99 export limits

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Insights for SA18

Figures below are tailored to SA18 — click through for full league tables.

Big-Roof Britain Rank #605 of 2182
5.5 kWp (UK avg 5.1 kWp)
~12 panels (≈430 W)
Solar Payback Index Rank #2017 of 2996
11.0 years (UK avg 10.8 years)
~£740 /yr • £8,139 upfront
Standing-Charge Drag Rank #1953 of 2996
28.5% (UK avg 26.6%) drag on savings
£211 fixed • ~£740 /yr value
Aspect Penalty View ranking →
East −19.1% West −18.3%
Typical output loss versus a south-facing roof (lower is better)

Seasonal solar output in SA18

Monthly generation per kilowatt of solar panels

kWh 33 Jan 47 Feb 80 Mar 107 Apr 113 May 110 Jun 105 Jul 95 Aug 82 Sep 55 Oct 39 Nov 29 Dec
Best month Worst month Winter (Dec–Feb) Other months

Winter output: 48.5% of an average month (Dec–Feb)

Best / worst month: May / Dec

These figures show output per kilowatt (kW) of panels installed. In winter, a 1 kW system here produces about 36 kWh per month; the average month produces around 75 kWh. So a typical 4 kW home system would generate roughly 145 kWh in winter, or 298 kWh in an average month.

Your Area at a Glance

Your Electricity Rate
26.33p/kWh
Daily Fixed Charge
57.84p/day
Local Sunshine
895kWh/kW
A 1 kW system generates ~895 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: 73% • Flats: 11% • Bungalows: 16% Based on 8,275 properties

Coverage

Carmarthenshire (86%)|Neath Port Talbot (12%)|Swansea (2%)

Areas Covered

Ammanford, Llandybie, Gwaun-Cae-Gurwen and Lower Brynamman, Saron, Garnant, Betws, Glanamman, Tycroes + 4 more

Data Sources & Assumptions

Solar yield: PVGIS (EU Joint Research Centre), January 2025 data

Electricity rates: Ofgem price cap, Q3 2026

Installation costs: DESNZ/MCS data, March 2026 (TIC)

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

SA8 (Neath Port Talbot)
≈12.5 km away
Local sunshine: ~888 kWh/kWp · -1% vs SA18
SA14 (Carmarthenshire)
≈13.6 km away
Local sunshine: ~948 kWh/kWp · +6% vs SA18
SA99 (Swansea)
≈14.1 km away
Local sunshine: ~968 kWh/kWp · +8% vs SA18
SA9 (Powys)
≈14.4 km away
Local sunshine: ~873 kWh/kWp · -2% vs SA18
SA4 (Swansea)
≈14.5 km away
Local sunshine: ~961 kWh/kWp · +7% vs SA18
SA6 (Swansea)
≈14.5 km away
Local sunshine: ~968 kWh/kWp · +8% vs SA18

Similar sunshine across the UK

S33 (High Peak)
~896 kWh/kWp · +0% vs SA18
KY4 (Fife)
~896 kWh/kWp · +0% vs SA18
AB31 (Aberdeenshire)
~896 kWh/kWp · +0% vs SA18