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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in CF47 (Merthyr Tydfil)

See if solar pays off for you in Merthyr Tydfil — price, savings and payback in under a minute (official UK data).

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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
13.3 years
After this, it's pure profit
Upfront Cost
£8,138
What you pay to get started
Annual Benefit
£612
What you save every year
Profit Over 25 Years
£7,169
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 915 kWh/kW — 54 below the regional median (968).

Read the full story

A typical roof here lands around 4.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 915 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)
915 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: £765, Upfront: £10,173, Break-even: 13.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1830 kWh 732 kWh 1098 kWh £196 £110 £306 £4,069 13.3 yrs £2,054
3 kW 2745 kWh 1098 kWh 1647 kWh £295 £165 £459 £6,104 13.3 yrs £3,081
4 kW 3659 kWh 1464 kWh 2196 kWh £393 £220 £612 £8,138 13.3 yrs £4,108
5 kW 4574 kWh 1830 kWh 2745 kWh £491 £274 £765 £10,173 13.3 yrs £5,135
6 kW 5489 kWh 2196 kWh 3293 kWh £589 £329 £918 £12,207 13.3 yrs £6,161
7 kW 6404 kWh 2562 kWh 3842 kWh £687 £384 £1,071 £14,242 13.3 yrs £7,188
8 kW 7319 kWh 2927 kWh 4391 kWh £785 £439 £1,225 £16,276 13.3 yrs £8,215

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: £919, Upfront: £12,273, Break-even: 13.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1830 kWh 1098 kWh 732 kWh £295 £73 £368 £6,169 16.8 yrs £1,186
3 kW 2745 kWh 1647 kWh 1098 kWh £442 £110 £552 £8,204 14.9 yrs £2,828
4 kW 3659 kWh 2196 kWh 1464 kWh £589 £146 £735 £10,238 13.9 yrs £4,471
5 kW 4574 kWh 2745 kWh 1830 kWh £736 £183 £919 £12,273 13.3 yrs £6,114
6 kW 5489 kWh 3293 kWh 2196 kWh £884 £220 £1,103 £14,307 13.0 yrs £7,757
7 kW 6404 kWh 3842 kWh 2562 kWh £1,031 £256 £1,287 £16,342 12.7 yrs £9,399
8 kW 7319 kWh 4391 kWh 2927 kWh £1,178 £293 £1,471 £18,376 12.5 yrs £11,042

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: £996, Upfront: £13,673, Break-even: 13.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1830 kWh 1281 kWh 549 kWh £344 £55 £399 £7,569 19.0 yrs £401
3 kW 2745 kWh 1921 kWh 823 kWh £515 £82 £598 £9,604 16.1 yrs £2,352
4 kW 3659 kWh 2562 kWh 1098 kWh £687 £110 £797 £11,638 14.6 yrs £4,303
5 kW 4574 kWh 3202 kWh 1372 kWh £859 £137 £996 £13,673 13.7 yrs £6,254
6 kW 5489 kWh 3842 kWh 1647 kWh £1,031 £165 £1,196 £15,707 13.1 yrs £8,204
7 kW 6404 kWh 4483 kWh 1921 kWh £1,203 £192 £1,395 £17,742 12.7 yrs £10,155
8 kW 7319 kWh 5123 kWh 2196 kWh £1,375 £220 £1,594 £19,776 12.4 yrs £12,106

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: £1,019, Upfront: £15,423, Break-even: 15.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1830 kWh 1336 kWh 494 kWh £358 £49 £408 £9,319 22.9 yrs £-1,164
3 kW 2745 kWh 2003 kWh 741 kWh £538 £74 £612 £11,354 18.6 yrs £879
4 kW 3659 kWh 2671 kWh 988 kWh £717 £99 £816 £13,388 16.4 yrs £2,922
5 kW 4574 kWh 3339 kWh 1235 kWh £896 £124 £1,019 £15,423 15.1 yrs £4,965
6 kW 5489 kWh 4007 kWh 1482 kWh £1,075 £148 £1,223 £17,457 14.3 yrs £7,009
7 kW 6404 kWh 4675 kWh 1729 kWh £1,254 £173 £1,427 £19,492 13.7 yrs £9,052
8 kW 7319 kWh 5343 kWh 1976 kWh £1,433 £198 £1,631 £21,526 13.2 yrs £11,095

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: £1,035, Upfront: £17,173, Break-even: 16.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1830 kWh 1372 kWh 457 kWh £368 £46 £414 £11,069 26.7 yrs £-2,791
3 kW 2745 kWh 2058 kWh 686 kWh £552 £69 £621 £13,104 21.1 yrs £-686
4 kW 3659 kWh 2745 kWh 915 kWh £736 £91 £828 £15,138 18.3 yrs £1,419
5 kW 4574 kWh 3431 kWh 1144 kWh £920 £114 £1,035 £17,173 16.6 yrs £3,523
6 kW 5489 kWh 4117 kWh 1372 kWh £1,105 £137 £1,242 £19,207 15.5 yrs £5,628
7 kW 6404 kWh 4803 kWh 1601 kWh £1,289 £160 £1,449 £21,242 14.7 yrs £7,733
8 kW 7319 kWh 5489 kWh 1830 kWh £1,473 £183 £1,656 £23,276 14.1 yrs £9,837

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: £1,050, Upfront: £19,623, Break-even: 18.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1830 kWh 1409 kWh 421 kWh £378 £42 £420 £13,519 32.2 yrs £-5,117
3 kW 2745 kWh 2113 kWh 631 kWh £567 £63 £630 £15,554 24.7 yrs £-2,951
4 kW 3659 kWh 2818 kWh 842 kWh £756 £84 £840 £17,588 20.9 yrs £-785
5 kW 4574 kWh 3522 kWh 1052 kWh £945 £105 £1,050 £19,623 18.7 yrs £1,381
6 kW 5489 kWh 4227 kWh 1262 kWh £1,134 £126 £1,260 £21,657 17.2 yrs £3,548
7 kW 6404 kWh 4931 kWh 1473 kWh £1,323 £147 £1,470 £23,692 16.1 yrs £5,714
8 kW 7319 kWh 5635 kWh 1683 kWh £1,512 £168 £1,680 £25,726 15.3 yrs £7,880

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 CF47

Figures below are tailored to CF47 — click through for full league tables.

Big-Roof Britain Rank #1531 of 2182
4.7 kWp (UK avg 5.1 kWp)
~10 panels (≈430 W)
Solar Payback Index Rank #1736 of 2997
11.5 years (UK avg 11.3 years)
~£705 /yr • £8,138 upfront
Standing-Charge Drag Rank #2410 of 2997
26.8% (UK avg 21.7%) drag on savings
£189 fixed • ~£705 /yr value

Your Area at a Glance

Your Electricity Rate
26.83p/kWh
Daily Fixed Charge
51.69p/day
Local Sunshine
915kWh/kW
A 1 kW system generates ~915 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
4.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 83% • Flats: 11% • Bungalows: 4% Based on 7,438 properties

Coverage

Merthyr Tydfil (100%)

Areas Covered

Town, Park, Penydarren, Gurnos, Cyfarthfa, Dowlais and Pant

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

CF48 (Merthyr Tydfil)
≈1.1 km away
Local sunshine: ~899 kWh/kWp · -2% vs CF47
CF44 (Rhondda Cynon Taf)
≈6.2 km away
Local sunshine: ~903 kWh/kWp · -1% vs CF47
CF45 (Rhondda Cynon Taf)
≈8.3 km away
Local sunshine: ~898 kWh/kWp · -2% vs CF47
NP22 (Blaenau Gwent)
≈9.0 km away
Local sunshine: ~919 kWh/kWp · +0% vs CF47
NP24 (Caerphilly)
≈10.0 km away
Local sunshine: ~881 kWh/kWp · -4% vs CF47
CF46 (Merthyr Tydfil)
≈10.9 km away
Local sunshine: ~939 kWh/kWp · +3% vs CF47

Similar sunshine across the UK

LS16 (Leeds)
~915 kWh/kWp · -0% vs CF47
LS18 (Leeds)
~915 kWh/kWp · -0% vs CF47
LS5 (Leeds)
~915 kWh/kWp · +0% vs CF47