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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in GU4 (Guildford)

See if solar pays off for you in Guildford — 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
12.3 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£993
What you save every year
Profit Over 25 Years
£12,625
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 East, the current unit rate is 26.92p/kWh with a 47.60p/day standing charge. Your postcode’s south-facing sunshine yield is 987 kWh/kW — 42 below the regional median (1029).

Read the full story

A typical roof here lands around 6.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 987 kWh per year on a south-facing roof. We value self-used electricity at 26.9p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.9p/kWh
Standing charge
47.6p/day
Sunshine yield (south)
987 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: £828, Upfront: £10,173, Break-even: 12.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1975 kWh 790 kWh 1185 kWh £213 £118 £331 £4,069 12.3 yrs £2,553
3 kW 2962 kWh 1185 kWh 1777 kWh £319 £178 £497 £6,104 12.3 yrs £3,829
4 kW 3949 kWh 1580 kWh 2369 kWh £425 £237 £662 £8,138 12.3 yrs £5,106
5 kW 4936 kWh 1975 kWh 2962 kWh £532 £296 £828 £10,173 12.3 yrs £6,382
6 kW 5924 kWh 2369 kWh 3554 kWh £638 £355 £993 £12,207 12.3 yrs £7,659
7 kW 6911 kWh 2764 kWh 4147 kWh £744 £415 £1,159 £14,242 12.3 yrs £8,935
8 kW 7898 kWh 3159 kWh 4739 kWh £850 £474 £1,324 £16,276 12.3 yrs £10,212

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: £995, Upfront: £12,273, Break-even: 12.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1975 kWh 1185 kWh 790 kWh £319 £79 £398 £6,169 15.5 yrs £1,789
3 kW 2962 kWh 1777 kWh 1185 kWh £478 £118 £597 £8,204 13.7 yrs £3,734
4 kW 3949 kWh 2369 kWh 1580 kWh £638 £158 £796 £10,238 12.9 yrs £5,679
5 kW 4936 kWh 2962 kWh 1975 kWh £797 £197 £995 £12,273 12.3 yrs £7,623
6 kW 5924 kWh 3554 kWh 2369 kWh £957 £237 £1,194 £14,307 12.0 yrs £9,568
7 kW 6911 kWh 4147 kWh 2764 kWh £1,116 £276 £1,393 £16,342 11.7 yrs £11,513
8 kW 7898 kWh 4739 kWh 3159 kWh £1,276 £316 £1,592 £18,376 11.5 yrs £13,457

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: £1,078, Upfront: £13,673, Break-even: 12.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1975 kWh 1382 kWh 592 kWh £372 £59 £431 £7,569 17.5 yrs £1,058
3 kW 2962 kWh 2073 kWh 889 kWh £558 £89 £647 £9,604 14.8 yrs £3,336
4 kW 3949 kWh 2764 kWh 1185 kWh £744 £118 £863 £11,638 13.5 yrs £5,615
5 kW 4936 kWh 3456 kWh 1481 kWh £930 £148 £1,078 £13,673 12.7 yrs £7,894
6 kW 5924 kWh 4147 kWh 1777 kWh £1,116 £178 £1,294 £15,707 12.1 yrs £10,173
7 kW 6911 kWh 4838 kWh 2073 kWh £1,302 £207 £1,510 £17,742 11.8 yrs £12,451
8 kW 7898 kWh 5529 kWh 2369 kWh £1,488 £237 £1,725 £19,776 11.5 yrs £14,730

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: £1,103, Upfront: £15,423, Break-even: 14.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1975 kWh 1441 kWh 533 kWh £388 £53 £441 £9,319 21.1 yrs £-492
3 kW 2962 kWh 2162 kWh 800 kWh £582 £80 £662 £11,354 17.1 yrs £1,887
4 kW 3949 kWh 2883 kWh 1066 kWh £776 £107 £883 £13,388 15.2 yrs £4,266
5 kW 4936 kWh 3604 kWh 1333 kWh £970 £133 £1,103 £15,423 14.0 yrs £6,645
6 kW 5924 kWh 4324 kWh 1599 kWh £1,164 £160 £1,324 £17,457 13.2 yrs £9,024
7 kW 6911 kWh 5045 kWh 1866 kWh £1,358 £187 £1,545 £19,492 12.6 yrs £11,403
8 kW 7898 kWh 5766 kWh 2133 kWh £1,552 £213 £1,765 £21,526 12.2 yrs £13,782

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: £1,120, Upfront: £17,173, Break-even: 15.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1975 kWh 1481 kWh 494 kWh £399 £49 £448 £11,069 24.7 yrs £-2,108
3 kW 2962 kWh 2221 kWh 740 kWh £598 £74 £672 £13,104 19.5 yrs £337
4 kW 3949 kWh 2962 kWh 987 kWh £797 £99 £896 £15,138 16.9 yrs £2,783
5 kW 4936 kWh 3702 kWh 1234 kWh £997 £123 £1,120 £17,173 15.3 yrs £5,229
6 kW 5924 kWh 4443 kWh 1481 kWh £1,196 £148 £1,344 £19,207 14.3 yrs £7,675
7 kW 6911 kWh 5183 kWh 1728 kWh £1,395 £173 £1,568 £21,242 13.5 yrs £10,121
8 kW 7898 kWh 5924 kWh 1975 kWh £1,595 £197 £1,792 £23,276 13.0 yrs £12,566

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: £1,137, Upfront: £19,623, Break-even: 17.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1975 kWh 1520 kWh 454 kWh £409 £45 £455 £13,519 29.7 yrs £-4,425
3 kW 2962 kWh 2281 kWh 681 kWh £614 £68 £682 £15,554 22.8 yrs £-1,912
4 kW 3949 kWh 3041 kWh 908 kWh £819 £91 £909 £17,588 19.3 yrs £601
5 kW 4936 kWh 3801 kWh 1135 kWh £1,023 £114 £1,137 £19,623 17.3 yrs £3,113
6 kW 5924 kWh 4561 kWh 1362 kWh £1,228 £136 £1,364 £21,657 15.9 yrs £5,626
7 kW 6911 kWh 5321 kWh 1590 kWh £1,433 £159 £1,591 £23,692 14.9 yrs £8,138
8 kW 7898 kWh 6082 kWh 1817 kWh £1,637 £182 £1,819 £25,726 14.1 yrs £10,651

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 GU4

Figures below are tailored to GU4 — click through for full league tables.

Big-Roof Britain Rank #949 of 2182
5.1 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #798 of 2997
10.7 years (UK avg 11.3 years)
~£1,144 /yr • £12,207 upfront
Standing-Charge Drag Rank #321 of 2997
15.2% (UK avg 21.7%) drag on savings
£174 fixed • ~£1,144 /yr value

Your Area at a Glance

Your Electricity Rate
26.92p/kWh
Daily Fixed Charge
47.60p/day
Local Sunshine
987kWh/kW
A 1 kW system generates ~987 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
6.0kW
For houses & bungalows in this area

Local Property Data

Property Types

Houses: 70% • Flats: 17% • Bungalows: 9% Based on 3,908 properties

Coverage

Guildford (96%)|Woking (2%)|Waverley (2%)

Areas Covered

Shalford, Burpham, Merrow, Stoke, Clandon & Horsley, Tillingbourne, Worplesdon, Castle + 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 East

GU1 (Guildford)
≈2.0 km away
Local sunshine: ~997 kWh/kWp · +1% vs GU4
GU2 (Guildford)
≈3.2 km away
Local sunshine: ~994 kWh/kWp · +1% vs GU4
GU3 (Guildford)
≈5.0 km away
Local sunshine: ~999 kWh/kWp · +1% vs GU4
GU5 (Guildford)
≈5.3 km away
Local sunshine: ~997 kWh/kWp · +1% vs GU4
GU23 (Guildford)
≈5.9 km away
Local sunshine: ~997 kWh/kWp · +1% vs GU4
GU22 (Woking)
≈7.8 km away
Local sunshine: ~996 kWh/kWp · +1% vs GU4

Similar sunshine across the UK

GU16 (Surrey Heath)
~987 kWh/kWp · +0% vs GU4
WD7 (Hertsmere)
~987 kWh/kWp · -0% vs GU4
LU7 (Central Bedfordshire)
~987 kWh/kWp · +0% vs GU4