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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in CF23 (Cardiff)

See if solar pays off for you in Cardiff — 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
12.1 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£840
What you save every year
Profit Over 25 Years
£10,832
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 1004 kWh/kW — 36 above 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 1004 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)
1004 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: £840, Upfront: £10,173, 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 2009 kWh 803 kWh 1205 kWh £216 £121 £336 £4,069 12.1 yrs £2,652
3 kW 3013 kWh 1205 kWh 1808 kWh £323 £181 £504 £6,104 12.1 yrs £3,979
4 kW 4017 kWh 1607 kWh 2410 kWh £431 £241 £672 £8,138 12.1 yrs £5,305
5 kW 5021 kWh 2009 kWh 3013 kWh £539 £301 £840 £10,173 12.1 yrs £6,631
6 kW 6026 kWh 2410 kWh 3615 kWh £647 £362 £1,008 £12,207 12.1 yrs £7,957
7 kW 7030 kWh 2812 kWh 4218 kWh £754 £422 £1,176 £14,242 12.1 yrs £9,283
8 kW 8034 kWh 3214 kWh 4821 kWh £862 £482 £1,344 £16,276 12.1 yrs £10,610

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: £1,009, Upfront: £12,273, Break-even: 12.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2009 kWh 1205 kWh 803 kWh £323 £80 £404 £6,169 15.3 yrs £1,905
3 kW 3013 kWh 1808 kWh 1205 kWh £485 £121 £606 £8,204 13.5 yrs £3,907
4 kW 4017 kWh 2410 kWh 1607 kWh £647 £161 £807 £10,238 12.7 yrs £5,909
5 kW 5021 kWh 3013 kWh 2009 kWh £808 £201 £1,009 £12,273 12.2 yrs £7,911
6 kW 6026 kWh 3615 kWh 2410 kWh £970 £241 £1,211 £14,307 11.8 yrs £9,914
7 kW 7030 kWh 4218 kWh 2812 kWh £1,132 £281 £1,413 £16,342 11.6 yrs £11,916
8 kW 8034 kWh 4821 kWh 3214 kWh £1,293 £321 £1,615 £18,376 11.4 yrs £13,918

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: £1,094, Upfront: £13,673, Break-even: 12.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2009 kWh 1406 kWh 603 kWh £377 £60 £437 £7,569 17.3 yrs £1,181
3 kW 3013 kWh 2109 kWh 904 kWh £566 £90 £656 £9,604 14.6 yrs £3,521
4 kW 4017 kWh 2812 kWh 1205 kWh £754 £121 £875 £11,638 13.3 yrs £5,861
5 kW 5021 kWh 3515 kWh 1506 kWh £943 £151 £1,094 £13,673 12.5 yrs £8,202
6 kW 6026 kWh 4218 kWh 1808 kWh £1,132 £181 £1,312 £15,707 12.0 yrs £10,542
7 kW 7030 kWh 4921 kWh 2109 kWh £1,320 £211 £1,531 £17,742 11.6 yrs £12,882
8 kW 8034 kWh 5624 kWh 2410 kWh £1,509 £241 £1,750 £19,776 11.3 yrs £15,223

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: £1,119, Upfront: £15,423, 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 2009 kWh 1466 kWh 542 kWh £393 £54 £448 £9,319 20.8 yrs £-367
3 kW 3013 kWh 2199 kWh 813 kWh £590 £81 £671 £11,354 16.9 yrs £2,075
4 kW 4017 kWh 2932 kWh 1085 kWh £787 £108 £895 £13,388 15.0 yrs £4,517
5 kW 5021 kWh 3666 kWh 1356 kWh £983 £136 £1,119 £15,423 13.8 yrs £6,959
6 kW 6026 kWh 4399 kWh 1627 kWh £1,180 £163 £1,343 £17,457 13.0 yrs £9,400
7 kW 7030 kWh 5132 kWh 1898 kWh £1,377 £190 £1,567 £19,492 12.4 yrs £11,842
8 kW 8034 kWh 5865 kWh 2169 kWh £1,574 £217 £1,791 £21,526 12.0 yrs £14,284

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: £1,136, Upfront: £17,173, 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 2009 kWh 1506 kWh 502 kWh £404 £50 £454 £11,069 24.4 yrs £-1,981
3 kW 3013 kWh 2260 kWh 753 kWh £606 £75 £682 £13,104 19.2 yrs £528
4 kW 4017 kWh 3013 kWh 1004 kWh £808 £100 £909 £15,138 16.7 yrs £3,037
5 kW 5021 kWh 3766 kWh 1255 kWh £1,010 £126 £1,136 £17,173 15.1 yrs £5,547
6 kW 6026 kWh 4519 kWh 1506 kWh £1,213 £151 £1,363 £19,207 14.1 yrs £8,056
7 kW 7030 kWh 5272 kWh 1757 kWh £1,415 £176 £1,590 £21,242 13.4 yrs £10,565
8 kW 8034 kWh 6026 kWh 2009 kWh £1,617 £201 £1,818 £23,276 12.8 yrs £13,075

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: £1,153, Upfront: £19,623, Break-even: 17.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2009 kWh 1547 kWh 462 kWh £415 £46 £461 £13,519 29.3 yrs £-4,296
3 kW 3013 kWh 2320 kWh 693 kWh £622 £69 £692 £15,554 22.5 yrs £-1,719
4 kW 4017 kWh 3093 kWh 924 kWh £830 £92 £922 £17,588 19.1 yrs £858
5 kW 5021 kWh 3866 kWh 1155 kWh £1,037 £115 £1,153 £19,623 17.0 yrs £3,435
6 kW 6026 kWh 4640 kWh 1386 kWh £1,245 £139 £1,383 £21,657 15.7 yrs £6,012
7 kW 7030 kWh 5413 kWh 1617 kWh £1,452 £162 £1,614 £23,692 14.7 yrs £8,589
8 kW 8034 kWh 6186 kWh 1848 kWh £1,660 £185 £1,845 £25,726 13.9 yrs £11,166

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 CF23

Figures below are tailored to CF23 — click through for full league tables.

Big-Roof Britain Rank #1123 of 2182
5.0 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #492 of 2997
10.5 years (UK avg 11.3 years)
~£967 /yr • £10,173 upfront
Standing-Charge Drag Rank #1298 of 2997
19.5% (UK avg 21.7%) drag on savings
£189 fixed • ~£967 /yr value

Your Area at a Glance

Your Electricity Rate
26.83p/kWh
Daily Fixed Charge
51.69p/day
Local Sunshine
1004kWh/kW
A 1 kW system generates ~1004 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: 66% • Flats: 31% • Bungalows: 3% Based on 10,615 properties

Coverage

Cardiff (95%)|Newport (5%)

Areas Covered

Penylan, Trowbridge, Cyncoed, Pentwyn, Pontprennau and Old St Mellons, Tredegar Park and Marshfield, Plasnewydd, Heath + 1 more

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

CF2 (Cardiff)
≈2.1 km away
Local sunshine: ~1,009 kWh/kWp · +0% vs CF23
CF3 (Cardiff)
≈2.3 km away
Local sunshine: ~1,004 kWh/kWp · +0% vs CF23
CF30 (Cardiff)
≈2.4 km away
Local sunshine: ~1,004 kWh/kWp · +0% vs CF23
CF24 (Cardiff)
≈2.8 km away
Local sunshine: ~1,009 kWh/kWp · +0% vs CF23
CF14 (Cardiff)
≈3.4 km away
Local sunshine: ~1,008 kWh/kWp · +0% vs CF23
CF95 (Cardiff)
≈3.6 km away
Local sunshine: ~1,009 kWh/kWp · +0% vs CF23

Similar sunshine across the UK

E6 (Newham)
~1,004 kWh/kWp · +0% vs CF23
PE19 (Huntingdonshire)
~1,004 kWh/kWp · +0% vs CF23
E13 (Newham)
~1,004 kWh/kWp · -0% vs CF23