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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in CF46 (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
12.9 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£786
What you save every year
Profit Over 25 Years
£9,470
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 939 kWh/kW — 29 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 939 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)
939 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: £786, Upfront: £10,173, Break-even: 12.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1878 kWh 751 kWh 1127 kWh £202 £113 £314 £4,069 12.9 yrs £2,216
3 kW 2817 kWh 1127 kWh 1690 kWh £302 £169 £471 £6,104 12.9 yrs £3,325
4 kW 3757 kWh 1503 kWh 2254 kWh £403 £225 £629 £8,138 12.9 yrs £4,433
5 kW 4696 kWh 1878 kWh 2817 kWh £504 £282 £786 £10,173 12.9 yrs £5,541
6 kW 5635 kWh 2254 kWh 3381 kWh £605 £338 £943 £12,207 12.9 yrs £6,649
7 kW 6574 kWh 2630 kWh 3944 kWh £706 £394 £1,100 £14,242 12.9 yrs £7,758
8 kW 7513 kWh 3005 kWh 4508 kWh £806 £451 £1,257 £16,276 12.9 yrs £8,866

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: £944, Upfront: £12,273, Break-even: 13.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1878 kWh 1127 kWh 751 kWh £302 £75 £377 £6,169 16.3 yrs £1,381
3 kW 2817 kWh 1690 kWh 1127 kWh £454 £113 £566 £8,204 14.5 yrs £3,121
4 kW 3757 kWh 2254 kWh 1503 kWh £605 £150 £755 £10,238 13.6 yrs £4,862
5 kW 4696 kWh 2817 kWh 1878 kWh £756 £188 £944 £12,273 13.0 yrs £6,602
6 kW 5635 kWh 3381 kWh 2254 kWh £907 £225 £1,132 £14,307 12.6 yrs £8,343
7 kW 6574 kWh 3944 kWh 2630 kWh £1,058 £263 £1,321 £16,342 12.4 yrs £10,083
8 kW 7513 kWh 4508 kWh 3005 kWh £1,209 £301 £1,510 £18,376 12.2 yrs £11,824

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: £1,023, Upfront: £13,673, Break-even: 13.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1878 kWh 1315 kWh 563 kWh £353 £56 £409 £7,569 18.5 yrs £613
3 kW 2817 kWh 1972 kWh 845 kWh £529 £85 £614 £9,604 15.6 yrs £2,670
4 kW 3757 kWh 2630 kWh 1127 kWh £706 £113 £818 £11,638 14.2 yrs £4,726
5 kW 4696 kWh 3287 kWh 1409 kWh £882 £141 £1,023 £13,673 13.4 yrs £6,783
6 kW 5635 kWh 3944 kWh 1690 kWh £1,058 £169 £1,227 £15,707 12.8 yrs £8,839
7 kW 6574 kWh 4602 kWh 1972 kWh £1,235 £197 £1,432 £17,742 12.4 yrs £10,896
8 kW 7513 kWh 5259 kWh 2254 kWh £1,411 £225 £1,636 £19,776 12.1 yrs £12,953

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: £1,046, Upfront: £15,423, Break-even: 14.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1878 kWh 1371 kWh 507 kWh £368 £51 £419 £9,319 22.3 yrs £-947
3 kW 2817 kWh 2057 kWh 761 kWh £552 £76 £628 £11,354 18.1 yrs £1,204
4 kW 3757 kWh 2742 kWh 1014 kWh £736 £101 £837 £13,388 16.0 yrs £3,356
5 kW 4696 kWh 3428 kWh 1268 kWh £920 £127 £1,046 £15,423 14.7 yrs £5,507
6 kW 5635 kWh 4113 kWh 1521 kWh £1,104 £152 £1,256 £17,457 13.9 yrs £7,658
7 kW 6574 kWh 4799 kWh 1775 kWh £1,288 £177 £1,465 £19,492 13.3 yrs £9,810
8 kW 7513 kWh 5485 kWh 2029 kWh £1,472 £203 £1,674 £21,526 12.9 yrs £11,961

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: £1,062, Upfront: £17,173, Break-even: 16.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1878 kWh 1409 kWh 470 kWh £378 £47 £425 £11,069 26.1 yrs £-2,571
3 kW 2817 kWh 2113 kWh 704 kWh £567 £70 £637 £13,104 20.6 yrs £-356
4 kW 3757 kWh 2817 kWh 939 kWh £756 £94 £850 £15,138 17.8 yrs £1,859
5 kW 4696 kWh 3522 kWh 1174 kWh £945 £117 £1,062 £17,173 16.2 yrs £4,073
6 kW 5635 kWh 4226 kWh 1409 kWh £1,134 £141 £1,275 £19,207 15.1 yrs £6,288
7 kW 6574 kWh 4930 kWh 1643 kWh £1,323 £164 £1,487 £21,242 14.3 yrs £8,502
8 kW 7513 kWh 5635 kWh 1878 kWh £1,512 £188 £1,700 £23,276 13.7 yrs £10,717

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: £1,078, Upfront: £19,623, Break-even: 18.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1878 kWh 1446 kWh 432 kWh £388 £43 £431 £13,519 31.3 yrs £-4,894
3 kW 2817 kWh 2169 kWh 648 kWh £582 £65 £647 £15,554 24.0 yrs £-2,616
4 kW 3757 kWh 2893 kWh 864 kWh £776 £86 £862 £17,588 20.4 yrs £-339
5 kW 4696 kWh 3616 kWh 1080 kWh £970 £108 £1,078 £19,623 18.2 yrs £1,939
6 kW 5635 kWh 4339 kWh 1296 kWh £1,164 £130 £1,294 £21,657 16.7 yrs £4,217
7 kW 6574 kWh 5062 kWh 1512 kWh £1,358 £151 £1,509 £23,692 15.7 yrs £6,495
8 kW 7513 kWh 5785 kWh 1728 kWh £1,552 £173 £1,725 £25,726 14.9 yrs £8,773

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 CF46

Figures below are tailored to CF46 — click through for full league tables.

Big-Roof Britain Rank #1158 of 2182
4.9 kWp (UK avg 5.1 kWp)
~10 panels (≈430 W)
Solar Payback Index Rank #1510 of 2997
11.2 years (UK avg 11.3 years)
~£904 /yr • £10,173 upfront
Standing-Charge Drag Rank #1588 of 2997
20.9% (UK avg 21.7%) drag on savings
£189 fixed • ~£904 /yr value

Your Area at a Glance

Your Electricity Rate
26.83p/kWh
Daily Fixed Charge
51.69p/day
Local Sunshine
939kWh/kW
A 1 kW system generates ~939 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: 82% • Flats: 8% • Bungalows: 10% Based on 3,313 properties

Coverage

Merthyr Tydfil (73%)|Caerphilly (26%)|Rhondda Cynon Taf (1%)

Areas Covered

Treharris, Bedlinog and Trelewis, Nelson, Graig and Pontypridd West, St Cattwg, Merthyr Vale, Plymouth, Ystrad Mynach

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

CF45 (Rhondda Cynon Taf)
≈4.8 km away
Local sunshine: ~898 kWh/kWp · -4% vs CF46
CF82 (Caerphilly)
≈5.0 km away
Local sunshine: ~934 kWh/kWp · -1% vs CF46
CF81 (Caerphilly)
≈5.9 km away
Local sunshine: ~935 kWh/kWp · -0% vs CF46
NP2 (Caerphilly)
≈7.3 km away
Local sunshine: ~918 kWh/kWp · -2% vs CF46
CF37 (Rhondda Cynon Taf)
≈7.3 km away
Local sunshine: ~940 kWh/kWp · +0% vs CF46
CF8 (Caerphilly)
≈7.4 km away
Local sunshine: ~988 kWh/kWp · +5% vs CF46

Similar sunshine across the UK

B62 (Dudley)
~939 kWh/kWp · +0% vs CF46
B11 (Birmingham)
~939 kWh/kWp · +0% vs CF46
S70 (Barnsley)
~939 kWh/kWp · -0% vs CF46