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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SO15 (Southampton)

See if solar pays off for you in Southampton — 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
11.9 years
After this, it's pure profit
Upfront Cost
£6,104
What you pay to get started
Annual Benefit
£514
What you save every year
Profit Over 25 Years
£6,743
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 1032 kWh/kW — 31 above the regional median (1001).

Read the full story

A typical roof here lands around 3.0 kW, with most eligible homes comfortably fitting within 3–6 kW. Each kilowatt of panels produces roughly 1032 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)
1032 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: £856, Upfront: £10,173, Break-even: 11.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2065 kWh 826 kWh 1239 kWh £219 £124 £343 £4,069 11.9 yrs £2,782
3 kW 3097 kWh 1239 kWh 1858 kWh £328 £186 £514 £6,104 11.9 yrs £4,174
4 kW 4129 kWh 1652 kWh 2478 kWh £437 £248 £685 £8,138 11.9 yrs £5,565
5 kW 5162 kWh 2065 kWh 3097 kWh £547 £310 £856 £10,173 11.9 yrs £6,956
6 kW 6194 kWh 2478 kWh 3716 kWh £656 £372 £1,028 £12,207 11.9 yrs £8,347
7 kW 7226 kWh 2891 kWh 4336 kWh £765 £434 £1,199 £14,242 11.9 yrs £9,739
8 kW 8259 kWh 3304 kWh 4955 kWh £875 £496 £1,370 £16,276 11.9 yrs £11,130

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: £1,027, Upfront: £12,273, Break-even: 12.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2065 kWh 1239 kWh 826 kWh £328 £83 £411 £6,169 15.0 yrs £2,044
3 kW 3097 kWh 1858 kWh 1239 kWh £492 £124 £616 £8,204 13.3 yrs £4,115
4 kW 4129 kWh 2478 kWh 1652 kWh £656 £165 £821 £10,238 12.5 yrs £6,187
5 kW 5162 kWh 3097 kWh 2065 kWh £820 £206 £1,027 £12,273 12.0 yrs £8,259
6 kW 6194 kWh 3716 kWh 2478 kWh £984 £248 £1,232 £14,307 11.6 yrs £10,331
7 kW 7226 kWh 4336 kWh 2891 kWh £1,148 £289 £1,437 £16,342 11.4 yrs £12,402
8 kW 8259 kWh 4955 kWh 3304 kWh £1,312 £330 £1,643 £18,376 11.2 yrs £14,474

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: £1,112, Upfront: £13,673, 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 2065 kWh 1445 kWh 619 kWh £383 £62 £445 £7,569 17.0 yrs £1,324
3 kW 3097 kWh 2168 kWh 929 kWh £574 £93 £667 £9,604 14.4 yrs £3,736
4 kW 4129 kWh 2891 kWh 1239 kWh £765 £124 £889 £11,638 13.1 yrs £6,148
5 kW 5162 kWh 3613 kWh 1549 kWh £957 £155 £1,112 £13,673 12.3 yrs £8,560
6 kW 6194 kWh 4336 kWh 1858 kWh £1,148 £186 £1,334 £15,707 11.8 yrs £10,972
7 kW 7226 kWh 5059 kWh 2168 kWh £1,339 £217 £1,556 £17,742 11.4 yrs £13,384
8 kW 8259 kWh 5781 kWh 2478 kWh £1,531 £248 £1,779 £19,776 11.1 yrs £15,796

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: £1,137, Upfront: £15,423, Break-even: 13.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2065 kWh 1507 kWh 557 kWh £399 £56 £455 £9,319 20.5 yrs £-222
3 kW 3097 kWh 2261 kWh 836 kWh £599 £84 £682 £11,354 16.6 yrs £2,292
4 kW 4129 kWh 3014 kWh 1115 kWh £798 £111 £910 £13,388 14.7 yrs £4,806
5 kW 5162 kWh 3768 kWh 1394 kWh £998 £139 £1,137 £15,423 13.6 yrs £7,321
6 kW 6194 kWh 4522 kWh 1672 kWh £1,197 £167 £1,365 £17,457 12.8 yrs £9,835
7 kW 7226 kWh 5275 kWh 1951 kWh £1,397 £195 £1,592 £19,492 12.2 yrs £12,349
8 kW 8259 kWh 6029 kWh 2230 kWh £1,596 £223 £1,819 £21,526 11.8 yrs £14,863

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: £1,154, Upfront: £17,173, 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 2065 kWh 1549 kWh 516 kWh £410 £52 £462 £11,069 24.0 yrs £-1,836
3 kW 3097 kWh 2323 kWh 774 kWh £615 £77 £693 £13,104 18.9 yrs £746
4 kW 4129 kWh 3097 kWh 1032 kWh £820 £103 £923 £15,138 16.4 yrs £3,329
5 kW 5162 kWh 3871 kWh 1290 kWh £1,025 £129 £1,154 £17,173 14.9 yrs £5,911
6 kW 6194 kWh 4646 kWh 1549 kWh £1,230 £155 £1,385 £19,207 13.9 yrs £8,493
7 kW 7226 kWh 5420 kWh 1807 kWh £1,435 £181 £1,616 £21,242 13.1 yrs £11,075
8 kW 8259 kWh 6194 kWh 2065 kWh £1,640 £206 £1,847 £23,276 12.6 yrs £13,657

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: £1,171, Upfront: £19,623, Break-even: 16.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2065 kWh 1590 kWh 475 kWh £421 £47 £468 £13,519 28.9 yrs £-4,150
3 kW 3097 kWh 2385 kWh 712 kWh £631 £71 £703 £15,554 22.1 yrs £-1,499
4 kW 4129 kWh 3180 kWh 950 kWh £842 £95 £937 £17,588 18.8 yrs £1,151
5 kW 5162 kWh 3975 kWh 1187 kWh £1,052 £119 £1,171 £19,623 16.8 yrs £3,801
6 kW 6194 kWh 4769 kWh 1425 kWh £1,263 £142 £1,405 £21,657 15.4 yrs £6,451
7 kW 7226 kWh 5564 kWh 1662 kWh £1,473 £166 £1,640 £23,692 14.4 yrs £9,101
8 kW 8259 kWh 6359 kWh 1900 kWh £1,684 £190 £1,874 £25,726 13.7 yrs £11,752

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 SO15

Figures below are tailored to SO15 — click through for full league tables.

Big-Roof Britain Rank #2162 of 2182
3.6 kWp (UK avg 5.1 kWp)
~8 panels (≈430 W)
Solar Payback Index Rank #350 of 2997
10.3 years (UK avg 11.3 years)
~£984 /yr • £10,173 upfront
Standing-Charge Drag Rank #656 of 2997
16.6% (UK avg 21.7%) drag on savings
£163 fixed • ~£984 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
1032kWh/kW
A 1 kW system generates ~1032 kWh per year. A typical home uses ~2,700 kWh per year.
Typical System Size
3.0kW
For houses & bungalows in this area

⚠️ This area is predominantly flats. Many residents require freeholder approval for solar installations. System size shown reflects houses and bungalows only.

Local Property Data

Property Types

Houses: 36% • Flats: 61% • Bungalows: 0% Based on 14,482 properties

Coverage

Southampton (100%)

Areas Covered

Freemantle, Banister & Polygon, Shirley, Millbrook, Redbridge, Bargate, Bassett

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

SO1 (Southampton)
≈0.6 km away
Local sunshine: ~1,050 kWh/kWp · +2% vs SO15
SO9 (Southampton)
≈1.8 km away
Local sunshine: ~1,050 kWh/kWp · +2% vs SO15
SO16 (Southampton)
≈2.1 km away
Local sunshine: ~1,031 kWh/kWp · -0% vs SO15
SO14 (Southampton)
≈2.5 km away
Local sunshine: ~1,037 kWh/kWp · +0% vs SO15
SO17 (Southampton)
≈2.6 km away
Local sunshine: ~1,031 kWh/kWp · -0% vs SO15
SO2 (Southampton)
≈4.2 km away
Local sunshine: ~1,031 kWh/kWp · -0% vs SO15

Similar sunshine across the UK

NR35 (East Suffolk)
~1,032 kWh/kWp · +0% vs SO15
PE36 (King's Lynn and West Norfolk)
~1,032 kWh/kWp · -0% vs SO15
TR6 (Cornwall)
~1,032 kWh/kWp · +0% vs SO15