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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in L34 (Knowsley)

See if solar pays off for you in Knowsley — 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
12.9 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£788
What you save every year
Profit Over 25 Years
£9,518
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 North Wales and Mersey, the current unit rate is 27.72p/kWh with a 69.95p/day standing charge. Your postcode’s south-facing sunshine yield is 922 kWh/kW — 8 below the regional median (930).

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 922 kWh per year on a south-facing roof. We value self-used electricity at 27.7p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
27.7p/kWh
Standing charge
70.0p/day
Sunshine yield (south)
922 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: £788, 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 1844 kWh 737 kWh 1106 kWh £204 £111 £315 £4,069 12.9 yrs £2,232
3 kW 2765 kWh 1106 kWh 1659 kWh £307 £166 £473 £6,104 12.9 yrs £3,348
4 kW 3687 kWh 1475 kWh 2212 kWh £409 £221 £630 £8,138 12.9 yrs £4,464
5 kW 4609 kWh 1844 kWh 2765 kWh £511 £277 £788 £10,173 12.9 yrs £5,580
6 kW 5531 kWh 2212 kWh 3319 kWh £613 £332 £945 £12,207 12.9 yrs £6,696
7 kW 6453 kWh 2581 kWh 3872 kWh £715 £387 £1,103 £14,242 12.9 yrs £7,812
8 kW 7375 kWh 2950 kWh 4425 kWh £818 £442 £1,260 £16,276 12.9 yrs £8,927

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: £951, Upfront: £12,273, 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 1844 kWh 1106 kWh 737 kWh £307 £74 £380 £6,169 16.2 yrs £1,439
3 kW 2765 kWh 1659 kWh 1106 kWh £460 £111 £571 £8,204 14.4 yrs £3,208
4 kW 3687 kWh 2212 kWh 1475 kWh £613 £147 £761 £10,238 13.5 yrs £4,977
5 kW 4609 kWh 2765 kWh 1844 kWh £767 £184 £951 £12,273 12.9 yrs £6,747
6 kW 5531 kWh 3319 kWh 2212 kWh £920 £221 £1,141 £14,307 12.5 yrs £8,516
7 kW 6453 kWh 3872 kWh 2581 kWh £1,073 £258 £1,331 £16,342 12.3 yrs £10,285
8 kW 7375 kWh 4425 kWh 2950 kWh £1,227 £295 £1,522 £18,376 12.1 yrs £12,055

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: £1,033, Upfront: £13,673, Break-even: 13.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1844 kWh 1291 kWh 553 kWh £358 £55 £413 £7,569 18.3 yrs £692
3 kW 2765 kWh 1936 kWh 830 kWh £537 £83 £620 £9,604 15.5 yrs £2,788
4 kW 3687 kWh 2581 kWh 1106 kWh £715 £111 £826 £11,638 14.1 yrs £4,884
5 kW 4609 kWh 3226 kWh 1383 kWh £894 £138 £1,033 £13,673 13.2 yrs £6,980
6 kW 5531 kWh 3872 kWh 1659 kWh £1,073 £166 £1,239 £15,707 12.7 yrs £9,076
7 kW 6453 kWh 4517 kWh 1936 kWh £1,252 £194 £1,446 £17,742 12.3 yrs £11,172
8 kW 7375 kWh 5162 kWh 2212 kWh £1,431 £221 £1,652 £19,776 12.0 yrs £13,268

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: £1,057, Upfront: £15,423, Break-even: 14.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1844 kWh 1346 kWh 498 kWh £373 £50 £423 £9,319 22.0 yrs £-862
3 kW 2765 kWh 2019 kWh 747 kWh £560 £75 £634 £11,354 17.9 yrs £1,332
4 kW 3687 kWh 2692 kWh 996 kWh £746 £100 £846 £13,388 15.8 yrs £3,526
5 kW 4609 kWh 3365 kWh 1244 kWh £933 £124 £1,057 £15,423 14.6 yrs £5,720
6 kW 5531 kWh 4038 kWh 1493 kWh £1,119 £149 £1,269 £17,457 13.8 yrs £7,914
7 kW 6453 kWh 4711 kWh 1742 kWh £1,306 £174 £1,480 £19,492 13.2 yrs £10,108
8 kW 7375 kWh 5383 kWh 1991 kWh £1,492 £199 £1,691 £21,526 12.7 yrs £12,302

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: £1,073, Upfront: £17,173, Break-even: 16.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1844 kWh 1383 kWh 461 kWh £383 £46 £429 £11,069 25.8 yrs £-2,481
3 kW 2765 kWh 2074 kWh 691 kWh £575 £69 £644 £13,104 20.3 yrs £-222
4 kW 3687 kWh 2765 kWh 922 kWh £767 £92 £859 £15,138 17.6 yrs £2,037
5 kW 4609 kWh 3457 kWh 1152 kWh £958 £115 £1,073 £17,173 16.0 yrs £4,297
6 kW 5531 kWh 4148 kWh 1383 kWh £1,150 £138 £1,288 £19,207 14.9 yrs £6,556
7 kW 6453 kWh 4840 kWh 1613 kWh £1,342 £161 £1,503 £21,242 14.1 yrs £8,816
8 kW 7375 kWh 5531 kWh 1844 kWh £1,533 £184 £1,718 £23,276 13.6 yrs £11,075

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: £1,090, Upfront: £19,623, Break-even: 18.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1844 kWh 1420 kWh 424 kWh £394 £42 £436 £13,519 31.0 yrs £-4,801
3 kW 2765 kWh 2129 kWh 636 kWh £590 £64 £654 £15,554 23.8 yrs £-2,476
4 kW 3687 kWh 2839 kWh 848 kWh £787 £85 £872 £17,588 20.2 yrs £-151
5 kW 4609 kWh 3549 kWh 1060 kWh £984 £106 £1,090 £19,623 18.0 yrs £2,174
6 kW 5531 kWh 4259 kWh 1272 kWh £1,181 £127 £1,308 £21,657 16.6 yrs £4,498
7 kW 6453 kWh 4969 kWh 1484 kWh £1,377 £148 £1,526 £23,692 15.5 yrs £6,823
8 kW 7375 kWh 5678 kWh 1696 kWh £1,574 £170 £1,744 £25,726 14.8 yrs £9,148

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 L34

Figures below are tailored to L34 — click through for full league tables.

Big-Roof Britain Rank #1348 of 2182
4.8 kWp (UK avg 5.1 kWp)
~10 panels (≈430 W)
Solar Payback Index Rank #1537 of 2997
11.2 years (UK avg 11.3 years)
~£910 /yr • £10,173 upfront
Standing-Charge Drag Rank #2572 of 2997
28.1% (UK avg 21.7%) drag on savings
£255 fixed • ~£910 /yr value

Your Area at a Glance

Your Electricity Rate
27.72p/kWh
Daily Fixed Charge
69.95p/day
Local Sunshine
922kWh/kW
A 1 kW system generates ~922 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: 64% • Flats: 24% • Bungalows: 7% Based on 5,223 properties

Coverage

Knowsley (91%)|St. Helens (9%)

Areas Covered

Prescot North, Eccleston, St Michaels, Stockbridge, Prescot South, Northwood, Windle

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 North Wales and Mersey

L35 (Knowsley)
≈1.7 km away
Local sunshine: ~914 kWh/kWp · -1% vs L34
L36 (Knowsley)
≈3.1 km away
Local sunshine: ~919 kWh/kWp · -0% vs L34
L28 (Knowsley)
≈4.1 km away
Local sunshine: ~926 kWh/kWp · +0% vs L34
WA10 (St. Helens)
≈4.5 km away
Local sunshine: ~911 kWh/kWp · -1% vs L34
L27 (Liverpool)
≈5.1 km away
Local sunshine: ~921 kWh/kWp · -0% vs L34
L14 (Liverpool)
≈5.1 km away
Local sunshine: ~926 kWh/kWp · +0% vs L34

Similar sunshine across the UK

NE4 (Newcastle upon Tyne)
~922 kWh/kWp · +0% vs L34
BT21 (Ards and North Down)
~922 kWh/kWp · +0% vs L34
SA38 (Carmarthenshire)
~922 kWh/kWp · -0% vs L34