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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in CF99 (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
£844
What you save every year
Profit Over 25 Years
£10,929
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 1009 kWh/kW — 40 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 1009 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)
1009 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: £844, 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 2018 kWh 807 kWh 1211 kWh £217 £121 £338 £4,069 12.1 yrs £2,683
3 kW 3027 kWh 1211 kWh 1816 kWh £325 £182 £506 £6,104 12.1 yrs £4,025
4 kW 4036 kWh 1614 kWh 2421 kWh £433 £242 £675 £8,138 12.1 yrs £5,367
5 kW 5045 kWh 2018 kWh 3027 kWh £541 £303 £844 £10,173 12.1 yrs £6,709
6 kW 6054 kWh 2421 kWh 3632 kWh £650 £363 £1,013 £12,207 12.1 yrs £8,050
7 kW 7062 kWh 2825 kWh 4237 kWh £758 £424 £1,182 £14,242 12.1 yrs £9,392
8 kW 8071 kWh 3229 kWh 4843 kWh £866 £484 £1,350 £16,276 12.1 yrs £10,734

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: £1,014, Upfront: £12,273, 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 2018 kWh 1211 kWh 807 kWh £325 £81 £406 £6,169 15.2 yrs £1,942
3 kW 3027 kWh 1816 kWh 1211 kWh £487 £121 £608 £8,204 13.5 yrs £3,963
4 kW 4036 kWh 2421 kWh 1614 kWh £650 £161 £811 £10,238 12.6 yrs £5,984
5 kW 5045 kWh 3027 kWh 2018 kWh £812 £202 £1,014 £12,273 12.1 yrs £8,005
6 kW 6054 kWh 3632 kWh 2421 kWh £974 £242 £1,217 £14,307 11.8 yrs £10,026
7 kW 7062 kWh 4237 kWh 2825 kWh £1,137 £282 £1,419 £16,342 11.5 yrs £12,047
8 kW 8071 kWh 4843 kWh 3229 kWh £1,299 £323 £1,622 £18,376 11.3 yrs £14,068

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: £1,099, Upfront: £13,673, Break-even: 12.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2018 kWh 1412 kWh 605 kWh £379 £61 £440 £7,569 17.2 yrs £1,221
3 kW 3027 kWh 2119 kWh 908 kWh £568 £91 £659 £9,604 14.6 yrs £3,582
4 kW 4036 kWh 2825 kWh 1211 kWh £758 £121 £879 £11,638 13.2 yrs £5,942
5 kW 5045 kWh 3531 kWh 1513 kWh £947 £151 £1,099 £13,673 12.4 yrs £8,303
6 kW 6054 kWh 4237 kWh 1816 kWh £1,137 £182 £1,319 £15,707 11.9 yrs £10,663
7 kW 7062 kWh 4944 kWh 2119 kWh £1,326 £212 £1,538 £17,742 11.5 yrs £13,024
8 kW 8071 kWh 5650 kWh 2421 kWh £1,516 £242 £1,758 £19,776 11.2 yrs £15,384

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: £1,124, Upfront: £15,423, 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 2018 kWh 1473 kWh 545 kWh £395 £54 £450 £9,319 20.7 yrs £-325
3 kW 3027 kWh 2210 kWh 817 kWh £593 £82 £675 £11,354 16.8 yrs £2,137
4 kW 4036 kWh 2946 kWh 1090 kWh £790 £109 £899 £13,388 14.9 yrs £4,600
5 kW 5045 kWh 3683 kWh 1362 kWh £988 £136 £1,124 £15,423 13.7 yrs £7,062
6 kW 6054 kWh 4419 kWh 1634 kWh £1,186 £163 £1,349 £17,457 12.9 yrs £9,525
7 kW 7062 kWh 5156 kWh 1907 kWh £1,383 £191 £1,574 £19,492 12.4 yrs £11,987
8 kW 8071 kWh 5892 kWh 2179 kWh £1,581 £218 £1,799 £21,526 12.0 yrs £14,449

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: £1,141, Upfront: £17,173, Break-even: 15.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2018 kWh 1513 kWh 504 kWh £406 £50 £456 £11,069 24.2 yrs £-1,939
3 kW 3027 kWh 2270 kWh 757 kWh £609 £76 £685 £13,104 19.1 yrs £591
4 kW 4036 kWh 3027 kWh 1009 kWh £812 £101 £913 £15,138 16.6 yrs £3,121
5 kW 5045 kWh 3783 kWh 1261 kWh £1,015 £126 £1,141 £17,173 15.0 yrs £5,652
6 kW 6054 kWh 4540 kWh 1513 kWh £1,218 £151 £1,369 £19,207 14.0 yrs £8,182
7 kW 7062 kWh 5297 kWh 1766 kWh £1,421 £177 £1,598 £21,242 13.3 yrs £10,712
8 kW 8071 kWh 6054 kWh 2018 kWh £1,624 £202 £1,826 £23,276 12.7 yrs £13,243

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: £1,158, Upfront: £19,623, Break-even: 16.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2018 kWh 1554 kWh 464 kWh £417 £46 £463 £13,519 29.2 yrs £-4,253
3 kW 3027 kWh 2331 kWh 696 kWh £625 £70 £695 £15,554 22.4 yrs £-1,655
4 kW 4036 kWh 3107 kWh 928 kWh £834 £93 £927 £17,588 19.0 yrs £943
5 kW 5045 kWh 3884 kWh 1160 kWh £1,042 £116 £1,158 £19,623 16.9 yrs £3,541
6 kW 6054 kWh 4661 kWh 1392 kWh £1,251 £139 £1,390 £21,657 15.6 yrs £6,140
7 kW 7062 kWh 5438 kWh 1624 kWh £1,459 £162 £1,621 £23,692 14.6 yrs £8,738
8 kW 8071 kWh 6215 kWh 1856 kWh £1,667 £186 £1,853 £25,726 13.9 yrs £11,336

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 CF99

Figures below are tailored to CF99 — click through for full league tables.

Solar Payback Index Rank #501 of 2997
10.5 years (UK avg 11.3 years)
~£971 /yr • £10,173 upfront
Standing-Charge Drag Rank #1277 of 2997
19.4% (UK avg 21.7%) drag on savings
£189 fixed • ~£971 /yr value

Your Area at a Glance

Your Electricity Rate
26.83p/kWh
Daily Fixed Charge
51.69p/day
Local Sunshine
1009kWh/kW
A 1 kW system generates ~1009 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

No EPC data available for this outcode

Coverage

Cardiff (100%)

Areas Covered

Butetown

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

CF10 (Cardiff)
≈1.4 km away
Local sunshine: ~1,009 kWh/kWp · +0% vs CF99
CF95 (Cardiff)
≈2.0 km away
Local sunshine: ~1,009 kWh/kWp · +0% vs CF99
CF1 (Cardiff)
≈2.1 km away
Local sunshine: ~1,009 kWh/kWp · +0% vs CF99
CF91 (Cardiff)
≈2.2 km away
Local sunshine: ~1,009 kWh/kWp · -0% vs CF99
CF11 (Cardiff)
≈2.2 km away
Local sunshine: ~1,006 kWh/kWp · -0% vs CF99
CF24 (Cardiff)
≈2.5 km away
Local sunshine: ~1,009 kWh/kWp · +0% vs CF99

Similar sunshine across the UK

BA6 (Somerset)
~1,009 kWh/kWp · -0% vs CF99
BA22 (Somerset)
~1,009 kWh/kWp · -0% vs CF99
NR21 (North Norfolk)
~1,009 kWh/kWp · +0% vs CF99