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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SO18 (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
11.8 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£860
What you save every year
Profit Over 25 Years
£11,334
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 1037 kWh/kW — 36 above the regional median (1001).

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 1037 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)
1037 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: £860, Upfront: £10,173, Break-even: 11.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2074 kWh 830 kWh 1244 kWh £220 £124 £344 £4,069 11.8 yrs £2,813
3 kW 3111 kWh 1244 kWh 1867 kWh £330 £187 £516 £6,104 11.8 yrs £4,220
4 kW 4148 kWh 1659 kWh 2489 kWh £439 £249 £688 £8,138 11.8 yrs £5,626
5 kW 5185 kWh 2074 kWh 3111 kWh £549 £311 £860 £10,173 11.8 yrs £7,033
6 kW 6222 kWh 2489 kWh 3733 kWh £659 £373 £1,032 £12,207 11.8 yrs £8,440
7 kW 7259 kWh 2904 kWh 4355 kWh £769 £436 £1,204 £14,242 11.8 yrs £9,846
8 kW 8296 kWh 3318 kWh 4978 kWh £879 £498 £1,376 £16,276 11.8 yrs £11,253

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: £1,031, Upfront: £12,273, 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 2074 kWh 1244 kWh 830 kWh £330 £83 £412 £6,169 15.0 yrs £2,080
3 kW 3111 kWh 1867 kWh 1244 kWh £494 £124 £619 £8,204 13.3 yrs £4,171
4 kW 4148 kWh 2489 kWh 1659 kWh £659 £166 £825 £10,238 12.4 yrs £6,261
5 kW 5185 kWh 3111 kWh 2074 kWh £824 £207 £1,031 £12,273 11.9 yrs £8,351
6 kW 6222 kWh 3733 kWh 2489 kWh £989 £249 £1,237 £14,307 11.6 yrs £10,441
7 kW 7259 kWh 4355 kWh 2904 kWh £1,153 £290 £1,444 £16,342 11.3 yrs £12,531
8 kW 8296 kWh 4978 kWh 3318 kWh £1,318 £332 £1,650 £18,376 11.1 yrs £14,621

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: £1,117, Upfront: £13,673, 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 2074 kWh 1452 kWh 622 kWh £384 £62 £447 £7,569 16.9 yrs £1,364
3 kW 3111 kWh 2178 kWh 933 kWh £577 £93 £670 £9,604 14.3 yrs £3,796
4 kW 4148 kWh 2904 kWh 1244 kWh £769 £124 £893 £11,638 13.0 yrs £6,228
5 kW 5185 kWh 3629 kWh 1555 kWh £961 £156 £1,117 £13,673 12.2 yrs £8,660
6 kW 6222 kWh 4355 kWh 1867 kWh £1,153 £187 £1,340 £15,707 11.7 yrs £11,092
7 kW 7259 kWh 5081 kWh 2178 kWh £1,346 £218 £1,563 £17,742 11.3 yrs £13,524
8 kW 8296 kWh 5807 kWh 2489 kWh £1,538 £249 £1,787 £19,776 11.1 yrs £15,956

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: £1,142, Upfront: £15,423, 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 2074 kWh 1514 kWh 560 kWh £401 £56 £457 £9,319 20.4 yrs £-181
3 kW 3111 kWh 2271 kWh 840 kWh £601 £84 £685 £11,354 16.6 yrs £2,354
4 kW 4148 kWh 3028 kWh 1120 kWh £802 £112 £914 £13,388 14.7 yrs £4,888
5 kW 5185 kWh 3785 kWh 1400 kWh £1,002 £140 £1,142 £15,423 13.5 yrs £7,423
6 kW 6222 kWh 4542 kWh 1680 kWh £1,203 £168 £1,371 £17,457 12.7 yrs £9,957
7 kW 7259 kWh 5299 kWh 1960 kWh £1,403 £196 £1,599 £19,492 12.2 yrs £12,492
8 kW 8296 kWh 6056 kWh 2240 kWh £1,604 £224 £1,828 £21,526 11.8 yrs £15,026

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: £1,159, Upfront: £17,173, Break-even: 14.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2074 kWh 1555 kWh 518 kWh £412 £52 £464 £11,069 23.9 yrs £-1,794
3 kW 3111 kWh 2333 kWh 778 kWh £618 £78 £696 £13,104 18.8 yrs £809
4 kW 4148 kWh 3111 kWh 1037 kWh £824 £104 £927 £15,138 16.3 yrs £3,411
5 kW 5185 kWh 3889 kWh 1296 kWh £1,030 £130 £1,159 £17,173 14.8 yrs £6,014
6 kW 6222 kWh 4666 kWh 1555 kWh £1,236 £156 £1,391 £19,207 13.8 yrs £8,617
7 kW 7259 kWh 5444 kWh 1815 kWh £1,442 £181 £1,623 £21,242 13.1 yrs £11,220
8 kW 8296 kWh 6222 kWh 2074 kWh £1,648 £207 £1,855 £23,276 12.5 yrs £13,823

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: £1,176, Upfront: £19,623, Break-even: 16.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2074 kWh 1597 kWh 477 kWh £423 £48 £471 £13,519 28.7 yrs £-4,108
3 kW 3111 kWh 2395 kWh 716 kWh £634 £72 £706 £15,554 22.0 yrs £-1,436
4 kW 4148 kWh 3194 kWh 954 kWh £846 £95 £941 £17,588 18.7 yrs £1,235
5 kW 5185 kWh 3992 kWh 1193 kWh £1,057 £119 £1,176 £19,623 16.7 yrs £3,906
6 kW 6222 kWh 4791 kWh 1431 kWh £1,269 £143 £1,412 £21,657 15.3 yrs £6,577
7 kW 7259 kWh 5589 kWh 1670 kWh £1,480 £167 £1,647 £23,692 14.4 yrs £9,249
8 kW 8296 kWh 6388 kWh 1908 kWh £1,691 £191 £1,882 £25,726 13.7 yrs £11,920

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 SO18

Figures below are tailored to SO18 — click through for full league tables.

Big-Roof Britain Rank #1946 of 2182
4.2 kWp (UK avg 5.1 kWp)
~9 panels (≈430 W)
Solar Payback Index Rank #351 of 2997
10.3 years (UK avg 11.3 years)
~£988 /yr • £10,173 upfront
Standing-Charge Drag Rank #633 of 2997
16.5% (UK avg 21.7%) drag on savings
£163 fixed • ~£988 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
1037kWh/kW
A 1 kW system generates ~1037 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: 47% • Flats: 38% • Bungalows: 7% Based on 9,512 properties

Coverage

Southampton (91%)|Eastleigh (9%)

Areas Covered

Bitterne Park, Harefield, West End South, Swaythling, Peartree, West End North, Bargate, Thornhill + 3 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

SO2 (Southampton)
≈0.3 km away
Local sunshine: ~1,031 kWh/kWp · -1% vs SO18
SO17 (Southampton)
≈1.9 km away
Local sunshine: ~1,031 kWh/kWp · -1% vs SO18
SO19 (Southampton)
≈2.0 km away
Local sunshine: ~1,063 kWh/kWp · +2% vs SO18
SO14 (Southampton)
≈2.5 km away
Local sunshine: ~1,037 kWh/kWp · -0% vs SO18
SO9 (Southampton)
≈2.7 km away
Local sunshine: ~1,050 kWh/kWp · +1% vs SO18
SO97 (Eastleigh)
≈3.2 km away
Local sunshine: ~1,038 kWh/kWp · +0% vs SO18

Similar sunshine across the UK

SS17 (Thurrock)
~1,037 kWh/kWp · -0% vs SO18
EX14 (East Devon)
~1,037 kWh/kWp · +0% vs SO18
EX2 (Exeter)
~1,038 kWh/kWp · +0% vs SO18