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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in NP11 (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
13.1 years
After this, it's pure profit
Upfront Cost
£8,138
What you pay to get started
Annual Benefit
£623
What you save every year
Profit Over 25 Years
£7,425
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 930 kWh/kW — 38 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 930 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)
930 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: £778, Upfront: £10,173, Break-even: 13.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1860 kWh 744 kWh 1116 kWh £200 £112 £311 £4,069 13.1 yrs £2,156
3 kW 2790 kWh 1116 kWh 1674 kWh £299 £167 £467 £6,104 13.1 yrs £3,234
4 kW 3721 kWh 1488 kWh 2232 kWh £399 £223 £623 £8,138 13.1 yrs £4,312
5 kW 4651 kWh 1860 kWh 2790 kWh £499 £279 £778 £10,173 13.1 yrs £5,390
6 kW 5581 kWh 2232 kWh 3348 kWh £599 £335 £934 £12,207 13.1 yrs £6,468
7 kW 6511 kWh 2604 kWh 3907 kWh £699 £391 £1,089 £14,242 13.1 yrs £7,547
8 kW 7441 kWh 2976 kWh 4465 kWh £799 £446 £1,245 £16,276 13.1 yrs £8,625

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: £935, Upfront: £12,273, Break-even: 13.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1860 kWh 1116 kWh 744 kWh £299 £74 £374 £6,169 16.5 yrs £1,308
3 kW 2790 kWh 1674 kWh 1116 kWh £449 £112 £561 £8,204 14.6 yrs £3,013
4 kW 3721 kWh 2232 kWh 1488 kWh £599 £149 £748 £10,238 13.7 yrs £4,717
5 kW 4651 kWh 2790 kWh 1860 kWh £749 £186 £935 £12,273 13.1 yrs £6,421
6 kW 5581 kWh 3348 kWh 2232 kWh £898 £223 £1,122 £14,307 12.8 yrs £8,125
7 kW 6511 kWh 3907 kWh 2604 kWh £1,048 £260 £1,309 £16,342 12.5 yrs £9,830
8 kW 7441 kWh 4465 kWh 2976 kWh £1,198 £298 £1,496 £18,376 12.3 yrs £11,534

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: £1,013, Upfront: £13,673, Break-even: 13.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1860 kWh 1302 kWh 558 kWh £349 £56 £405 £7,569 18.7 yrs £535
3 kW 2790 kWh 1953 kWh 837 kWh £524 £84 £608 £9,604 15.8 yrs £2,552
4 kW 3721 kWh 2604 kWh 1116 kWh £699 £112 £810 £11,638 14.4 yrs £4,569
5 kW 4651 kWh 3255 kWh 1395 kWh £873 £140 £1,013 £13,673 13.5 yrs £6,587
6 kW 5581 kWh 3907 kWh 1674 kWh £1,048 £167 £1,216 £15,707 12.9 yrs £8,604
7 kW 6511 kWh 4558 kWh 1953 kWh £1,223 £195 £1,418 £17,742 12.5 yrs £10,621
8 kW 7441 kWh 5209 kWh 2232 kWh £1,398 £223 £1,621 £19,776 12.2 yrs £12,639

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: £1,036, Upfront: £15,423, Break-even: 14.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1860 kWh 1358 kWh 502 kWh £364 £50 £415 £9,319 22.5 yrs £-1,028
3 kW 2790 kWh 2037 kWh 753 kWh £547 £75 £622 £11,354 18.3 yrs £1,084
4 kW 3721 kWh 2716 kWh 1005 kWh £729 £100 £829 £13,388 16.1 yrs £3,195
5 kW 4651 kWh 3395 kWh 1256 kWh £911 £126 £1,036 £15,423 14.9 yrs £5,306
6 kW 5581 kWh 4074 kWh 1507 kWh £1,093 £151 £1,244 £17,457 14.0 yrs £7,417
7 kW 6511 kWh 4753 kWh 1758 kWh £1,275 £176 £1,451 £19,492 13.4 yrs £9,529
8 kW 7441 kWh 5432 kWh 2009 kWh £1,457 £201 £1,658 £21,526 13.0 yrs £11,640

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: £1,052, Upfront: £17,173, Break-even: 16.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1860 kWh 1395 kWh 465 kWh £374 £47 £421 £11,069 26.3 yrs £-2,652
3 kW 2790 kWh 2093 kWh 698 kWh £561 £70 £631 £13,104 20.8 yrs £-478
4 kW 3721 kWh 2790 kWh 930 kWh £749 £93 £842 £15,138 18.0 yrs £1,695
5 kW 4651 kWh 3488 kWh 1163 kWh £936 £116 £1,052 £17,173 16.3 yrs £3,869
6 kW 5581 kWh 4186 kWh 1395 kWh £1,123 £140 £1,263 £19,207 15.2 yrs £6,043
7 kW 6511 kWh 4883 kWh 1628 kWh £1,310 £163 £1,473 £21,242 14.4 yrs £8,217
8 kW 7441 kWh 5581 kWh 1860 kWh £1,497 £186 £1,683 £23,276 13.8 yrs £10,391

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: £1,068, Upfront: £19,623, Break-even: 18.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1860 kWh 1432 kWh 428 kWh £384 £43 £427 £13,519 31.7 yrs £-4,977
3 kW 2790 kWh 2149 kWh 642 kWh £576 £64 £641 £15,554 24.3 yrs £-2,741
4 kW 3721 kWh 2865 kWh 856 kWh £769 £86 £854 £17,588 20.6 yrs £-504
5 kW 4651 kWh 3581 kWh 1070 kWh £961 £107 £1,068 £19,623 18.4 yrs £1,732
6 kW 5581 kWh 4297 kWh 1284 kWh £1,153 £128 £1,281 £21,657 16.9 yrs £3,969
7 kW 6511 kWh 5013 kWh 1498 kWh £1,345 £150 £1,495 £23,692 15.8 yrs £6,205
8 kW 7441 kWh 5730 kWh 1711 kWh £1,537 £171 £1,708 £25,726 15.1 yrs £8,442

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 NP11

Figures below are tailored to NP11 — click through for full league tables.

Big-Roof Britain Rank #1505 of 2182
4.7 kWp (UK avg 5.1 kWp)
~10 panels (≈430 W)
Solar Payback Index Rank #1709 of 2997
11.4 years (UK avg 11.3 years)
~£716 /yr • £8,138 upfront
Standing-Charge Drag Rank #2397 of 2997
26.4% (UK avg 21.7%) drag on savings
£189 fixed • ~£716 /yr value

Your Area at a Glance

Your Electricity Rate
26.83p/kWh
Daily Fixed Charge
51.69p/day
Local Sunshine
930kWh/kW
A 1 kW system generates ~930 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: 76% • Flats: 17% • Bungalows: 5% Based on 8,531 properties

Coverage

Caerphilly (97%)|Blaenau Gwent (3%)

Areas Covered

Newbridge, Abercarn, Crumlin, Risca West, Risca East, Ynysddu, Crosskeys, Llanhilleth + 2 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

NP12 (Caerphilly)
≈4.5 km away
Local sunshine: ~926 kWh/kWp · -0% vs NP11
NP1 (Caerphilly)
≈4.6 km away
Local sunshine: ~1,001 kWh/kWp · +8% vs NP11
CF82 (Caerphilly)
≈6.9 km away
Local sunshine: ~934 kWh/kWp · +0% vs NP11
CF8 (Caerphilly)
≈7.7 km away
Local sunshine: ~988 kWh/kWp · +6% vs NP11
NP44 (Torfaen)
≈7.8 km away
Local sunshine: ~971 kWh/kWp · +4% vs NP11
CF81 (Caerphilly)
≈8.3 km away
Local sunshine: ~935 kWh/kWp · +1% vs NP11

Similar sunshine across the UK

CH43 (Wirral)
~930 kWh/kWp · -0% vs NP11
CH1 (Cheshire West and Chester)
~930 kWh/kWp · +0% vs NP11
NE25 (North Tyneside)
~930 kWh/kWp · +0% vs NP11