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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in NP24 (Caerphilly)

See if solar pays off for you in Caerphilly — 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
13.8 years
After this, it's pure profit
Upfront Cost
£8,138
What you pay to get started
Annual Benefit
£589
What you save every year
Profit Over 25 Years
£6,597
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 881 kWh/kW — 88 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 881 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)
881 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: £737, Upfront: £10,173, 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 1761 kWh 705 kWh 1057 kWh £189 £106 £295 £4,069 13.8 yrs £1,825
3 kW 2642 kWh 1057 kWh 1585 kWh £284 £159 £442 £6,104 13.8 yrs £2,737
4 kW 3523 kWh 1409 kWh 2114 kWh £378 £211 £589 £8,138 13.8 yrs £3,650
5 kW 4403 kWh 1761 kWh 2642 kWh £473 £264 £737 £10,173 13.8 yrs £4,562
6 kW 5284 kWh 2114 kWh 3170 kWh £567 £317 £884 £12,207 13.8 yrs £5,475
7 kW 6164 kWh 2466 kWh 3699 kWh £662 £370 £1,031 £14,242 13.8 yrs £6,387
8 kW 7045 kWh 2818 kWh 4227 kWh £756 £423 £1,179 £16,276 13.8 yrs £7,300

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: £885, Upfront: £12,273, Break-even: 13.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1761 kWh 1057 kWh 705 kWh £284 £70 £354 £6,169 17.4 yrs £911
3 kW 2642 kWh 1585 kWh 1057 kWh £425 £106 £531 £8,204 15.4 yrs £2,416
4 kW 3523 kWh 2114 kWh 1409 kWh £567 £141 £708 £10,238 14.5 yrs £3,921
5 kW 4403 kWh 2642 kWh 1761 kWh £709 £176 £885 £12,273 13.9 yrs £5,427
6 kW 5284 kWh 3170 kWh 2114 kWh £851 £211 £1,062 £14,307 13.5 yrs £6,932
7 kW 6164 kWh 3699 kWh 2466 kWh £992 £247 £1,239 £16,342 13.2 yrs £8,437
8 kW 7045 kWh 4227 kWh 2818 kWh £1,134 £282 £1,416 £18,376 13.0 yrs £9,942

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: £959, Upfront: £13,673, Break-even: 14.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1761 kWh 1233 kWh 528 kWh £331 £53 £384 £7,569 19.7 yrs £103
3 kW 2642 kWh 1849 kWh 793 kWh £496 £79 £575 £9,604 16.7 yrs £1,905
4 kW 3523 kWh 2466 kWh 1057 kWh £662 £106 £767 £11,638 15.2 yrs £3,707
5 kW 4403 kWh 3082 kWh 1321 kWh £827 £132 £959 £13,673 14.3 yrs £5,509
6 kW 5284 kWh 3699 kWh 1585 kWh £992 £159 £1,151 £15,707 13.6 yrs £7,310
7 kW 6164 kWh 4315 kWh 1849 kWh £1,158 £185 £1,343 £17,742 13.2 yrs £9,112
8 kW 7045 kWh 4932 kWh 2114 kWh £1,323 £211 £1,534 £19,776 12.9 yrs £10,914

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: £981, Upfront: £15,423, Break-even: 15.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1761 kWh 1286 kWh 476 kWh £345 £48 £393 £9,319 23.7 yrs £-1,469
3 kW 2642 kWh 1929 kWh 713 kWh £517 £71 £589 £11,354 19.3 yrs £422
4 kW 3523 kWh 2571 kWh 951 kWh £690 £95 £785 £13,388 17.1 yrs £2,313
5 kW 4403 kWh 3214 kWh 1189 kWh £862 £119 £981 £15,423 15.7 yrs £4,203
6 kW 5284 kWh 3857 kWh 1427 kWh £1,035 £143 £1,178 £17,457 14.8 yrs £6,094
7 kW 6164 kWh 4500 kWh 1664 kWh £1,207 £166 £1,374 £19,492 14.2 yrs £7,985
8 kW 7045 kWh 5143 kWh 1902 kWh £1,380 £190 £1,570 £21,526 13.7 yrs £9,875

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: £996, Upfront: £17,173, Break-even: 17.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1761 kWh 1321 kWh 440 kWh £354 £44 £398 £11,069 27.8 yrs £-3,100
3 kW 2642 kWh 1981 kWh 660 kWh £532 £66 £598 £13,104 21.9 yrs £-1,150
4 kW 3523 kWh 2642 kWh 881 kWh £709 £88 £797 £15,138 19.0 yrs £800
5 kW 4403 kWh 3302 kWh 1101 kWh £886 £110 £996 £17,173 17.2 yrs £2,750
6 kW 5284 kWh 3963 kWh 1321 kWh £1,063 £132 £1,195 £19,207 16.1 yrs £4,700
7 kW 6164 kWh 4623 kWh 1541 kWh £1,240 £154 £1,395 £21,242 15.2 yrs £6,650
8 kW 7045 kWh 5284 kWh 1761 kWh £1,418 £176 £1,594 £23,276 14.6 yrs £8,600

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: £1,011, Upfront: £19,623, Break-even: 19.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1761 kWh 1356 kWh 405 kWh £364 £41 £404 £13,519 33.4 yrs £-5,432
3 kW 2642 kWh 2034 kWh 608 kWh £546 £61 £607 £15,554 25.6 yrs £-3,422
4 kW 3523 kWh 2712 kWh 810 kWh £728 £81 £809 £17,588 21.7 yrs £-1,413
5 kW 4403 kWh 3390 kWh 1013 kWh £910 £101 £1,011 £19,623 19.4 yrs £596
6 kW 5284 kWh 4069 kWh 1215 kWh £1,092 £122 £1,213 £21,657 17.9 yrs £2,605
7 kW 6164 kWh 4747 kWh 1418 kWh £1,274 £142 £1,415 £23,692 16.7 yrs £4,615
8 kW 7045 kWh 5425 kWh 1620 kWh £1,455 £162 £1,617 £25,726 15.9 yrs £6,624

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 NP24

Figures below are tailored to NP24 — click through for full league tables.

Big-Roof Britain Rank #1665 of 2182
4.5 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #2340 of 2997
12.0 years (UK avg 11.3 years)
~£678 /yr • £8,138 upfront
Standing-Charge Drag Rank #2513 of 2997
27.8% (UK avg 21.7%) drag on savings
£189 fixed • ~£678 /yr value

Your Area at a Glance

Your Electricity Rate
26.83p/kWh
Daily Fixed Charge
51.69p/day
Local Sunshine
881kWh/kW
A 1 kW system generates ~881 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: 84% • Flats: 9% • Bungalows: 6% Based on 1,392 properties

Coverage

Caerphilly (95%)|Blaenau Gwent (5%)

Areas Covered

New Tredegar, Tredegar

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

NP2 (Caerphilly)
≈2.1 km away
Local sunshine: ~918 kWh/kWp · +4% vs NP24
CF81 (Caerphilly)
≈3.1 km away
Local sunshine: ~935 kWh/kWp · +6% vs NP24
NP22 (Blaenau Gwent)
≈5.7 km away
Local sunshine: ~919 kWh/kWp · +4% vs NP24
NP12 (Caerphilly)
≈6.7 km away
Local sunshine: ~926 kWh/kWp · +5% vs NP24
NP13 (Blaenau Gwent)
≈7.3 km away
Local sunshine: ~933 kWh/kWp · +6% vs NP24
NP3 (Blaenau Gwent)
≈7.7 km away
Local sunshine: ~928 kWh/kWp · +5% vs NP24

Similar sunshine across the UK

BL7 (Bolton)
~881 kWh/kWp · -0% vs NP24
M38 (Salford)
~880 kWh/kWp · -0% vs NP24
M28 (Salford)
~881 kWh/kWp · +0% vs NP24