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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SO51 (Test Valley)

See if solar pays off for you in Test Valley — 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
£12,207
What you pay to get started
Annual Benefit
£1,010
What you save every year
Profit Over 25 Years
£13,045
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 Southern, the current unit rate is 26.48p/kWh with a 44.62p/day standing charge. Your postcode’s south-facing sunshine yield is 1015 kWh/kW — 13 above the regional median (1001).

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 1015 kWh per year on a south-facing roof. We value self-used electricity at 26.5p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
26.5p/kWh
Standing charge
44.6p/day
Sunshine yield (south)
1015 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: £842, 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 2029 kWh 812 kWh 1218 kWh £215 £122 £337 £4,069 12.1 yrs £2,665
3 kW 3044 kWh 1218 kWh 1826 kWh £322 £183 £505 £6,104 12.1 yrs £3,997
4 kW 4059 kWh 1623 kWh 2435 kWh £430 £244 £673 £8,138 12.1 yrs £5,330
5 kW 5073 kWh 2029 kWh 3044 kWh £537 £304 £842 £10,173 12.1 yrs £6,662
6 kW 6088 kWh 2435 kWh 3653 kWh £645 £365 £1,010 £12,207 12.1 yrs £7,995
7 kW 7102 kWh 2841 kWh 4261 kWh £752 £426 £1,178 £14,242 12.1 yrs £9,327
8 kW 8117 kWh 3247 kWh 4870 kWh £860 £487 £1,347 £16,276 12.1 yrs £10,660

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: £1,009, Upfront: £12,273, Break-even: 12.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2029 kWh 1218 kWh 812 kWh £322 £81 £404 £6,169 15.3 yrs £1,903
3 kW 3044 kWh 1826 kWh 1218 kWh £484 £122 £605 £8,204 13.6 yrs £3,904
4 kW 4059 kWh 2435 kWh 1623 kWh £645 £162 £807 £10,238 12.7 yrs £5,905
5 kW 5073 kWh 3044 kWh 2029 kWh £806 £203 £1,009 £12,273 12.2 yrs £7,906
6 kW 6088 kWh 3653 kWh 2435 kWh £967 £244 £1,211 £14,307 11.8 yrs £9,908
7 kW 7102 kWh 4261 kWh 2841 kWh £1,128 £284 £1,413 £16,342 11.6 yrs £11,909
8 kW 8117 kWh 4870 kWh 3247 kWh £1,290 £325 £1,614 £18,376 11.4 yrs £13,910

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: £1,093, Upfront: £13,673, Break-even: 12.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2029 kWh 1420 kWh 609 kWh £376 £61 £437 £7,569 17.3 yrs £1,171
3 kW 3044 kWh 2131 kWh 913 kWh £564 £91 £656 £9,604 14.6 yrs £3,507
4 kW 4059 kWh 2841 kWh 1218 kWh £752 £122 £874 £11,638 13.3 yrs £5,843
5 kW 5073 kWh 3551 kWh 1522 kWh £940 £152 £1,093 £13,673 12.5 yrs £8,179
6 kW 6088 kWh 4261 kWh 1826 kWh £1,128 £183 £1,311 £15,707 12.0 yrs £10,514
7 kW 7102 kWh 4972 kWh 2131 kWh £1,317 £213 £1,530 £17,742 11.6 yrs £12,850
8 kW 8117 kWh 5682 kWh 2435 kWh £1,505 £244 £1,748 £19,776 11.3 yrs £15,186

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: £1,118, Upfront: £15,423, 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 2029 kWh 1481 kWh 548 kWh £392 £55 £447 £9,319 20.8 yrs £-378
3 kW 3044 kWh 2222 kWh 822 kWh £588 £82 £671 £11,354 16.9 yrs £2,058
4 kW 4059 kWh 2963 kWh 1096 kWh £785 £110 £894 £13,388 15.0 yrs £4,494
5 kW 5073 kWh 3703 kWh 1370 kWh £981 £137 £1,118 £15,423 13.8 yrs £6,930
6 kW 6088 kWh 4444 kWh 1644 kWh £1,177 £164 £1,341 £17,457 13.0 yrs £9,366
7 kW 7102 kWh 5185 kWh 1918 kWh £1,373 £192 £1,565 £19,492 12.5 yrs £11,802
8 kW 8117 kWh 5925 kWh 2192 kWh £1,569 £219 £1,788 £21,526 12.0 yrs £14,238

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: £1,134, Upfront: £17,173, Break-even: 15.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2029 kWh 1522 kWh 507 kWh £403 £51 £454 £11,069 24.4 yrs £-1,994
3 kW 3044 kWh 2283 kWh 761 kWh £605 £76 £681 £13,104 19.3 yrs £509
4 kW 4059 kWh 3044 kWh 1015 kWh £806 £101 £907 £15,138 16.7 yrs £3,012
5 kW 5073 kWh 3805 kWh 1268 kWh £1,008 £127 £1,134 £17,173 15.1 yrs £5,515
6 kW 6088 kWh 4566 kWh 1522 kWh £1,209 £152 £1,361 £19,207 14.1 yrs £8,017
7 kW 7102 kWh 5327 kWh 1776 kWh £1,411 £178 £1,588 £21,242 13.4 yrs £10,520
8 kW 8117 kWh 6088 kWh 2029 kWh £1,612 £203 £1,815 £23,276 12.8 yrs £13,023

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: £1,151, Upfront: £19,623, Break-even: 17.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2029 kWh 1563 kWh 467 kWh £414 £47 £460 £13,519 29.4 yrs £-4,310
3 kW 3044 kWh 2344 kWh 700 kWh £621 £70 £691 £15,554 22.5 yrs £-1,741
4 kW 4059 kWh 3125 kWh 933 kWh £828 £93 £921 £17,588 19.1 yrs £829
5 kW 5073 kWh 3906 kWh 1167 kWh £1,034 £117 £1,151 £19,623 17.0 yrs £3,399
6 kW 6088 kWh 4688 kWh 1400 kWh £1,241 £140 £1,381 £21,657 15.7 yrs £5,969
7 kW 7102 kWh 5469 kWh 1634 kWh £1,448 £163 £1,612 £23,692 14.7 yrs £8,539
8 kW 8117 kWh 6250 kWh 1867 kWh £1,655 £187 £1,842 £25,726 14.0 yrs £11,108

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 SO51

Figures below are tailored to SO51 — click through for full league tables.

Big-Roof Britain Rank #773 of 2182
5.3 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #579 of 2997
10.5 years (UK avg 11.3 years)
~£1,161 /yr • £12,207 upfront
Standing-Charge Drag Rank #94 of 2997
14.0% (UK avg 21.7%) drag on savings
£163 fixed • ~£1,161 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
1015kWh/kW
A 1 kW system generates ~1015 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: 69% • Flats: 20% • Bungalows: 9% Based on 7,797 properties

Coverage

Test Valley (99%)|New Forest (1%)

Areas Covered

Romsey Abbey, Romsey Tadburn, Blackwater, Romsey Cupernham, Ampfield & Braishfield, Mid Test, Chilworth, Nursling & Rownhams + 6 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 Southern

SO52 (Test Valley)
≈4.0 km away
Local sunshine: ~1,025 kWh/kWp · +1% vs SO51
SO16 (Southampton)
≈7.5 km away
Local sunshine: ~1,031 kWh/kWp · +2% vs SO51
SO40 (New Forest)
≈7.9 km away
Local sunshine: ~1,035 kWh/kWp · +2% vs SO51
SO53 (Eastleigh)
≈8.2 km away
Local sunshine: ~1,024 kWh/kWp · +1% vs SO51
SO5 (Eastleigh)
≈8.5 km away
Local sunshine: ~1,022 kWh/kWp · +1% vs SO51
SO1 (Southampton)
≈9.0 km away
Local sunshine: ~1,050 kWh/kWp · +3% vs SO51

Similar sunshine across the UK

TA7 (Somerset)
~1,015 kWh/kWp · +0% vs SO51
IP33 (West Suffolk)
~1,015 kWh/kWp · +0% vs SO51
DA17 (Bexley)
~1,014 kWh/kWp · -0% vs SO51