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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in SP11 (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
12.2 years
After this, it's pure profit
Upfront Cost
£10,173
What you pay to get started
Annual Benefit
£834
What you save every year
Profit Over 25 Years
£10,669
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 1005 kWh/kW — 4 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 1005 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)
1005 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: £834, Upfront: £10,173, 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 2010 kWh 804 kWh 1206 kWh £213 £121 £333 £4,069 12.2 yrs £2,600
3 kW 3015 kWh 1206 kWh 1809 kWh £319 £181 £500 £6,104 12.2 yrs £3,900
4 kW 4020 kWh 1608 kWh 2412 kWh £426 £241 £667 £8,138 12.2 yrs £5,200
5 kW 5024 kWh 2010 kWh 3015 kWh £532 £301 £834 £10,173 12.2 yrs £6,500
6 kW 6029 kWh 2412 kWh 3618 kWh £639 £362 £1,000 £12,207 12.2 yrs £7,801
7 kW 7034 kWh 2814 kWh 4220 kWh £745 £422 £1,167 £14,242 12.2 yrs £9,101
8 kW 8039 kWh 3216 kWh 4823 kWh £851 £482 £1,334 £16,276 12.2 yrs £10,401

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: £999, 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 2010 kWh 1206 kWh 804 kWh £319 £80 £400 £6,169 15.4 yrs £1,825
3 kW 3015 kWh 1809 kWh 1206 kWh £479 £121 £600 £8,204 13.7 yrs £3,788
4 kW 4020 kWh 2412 kWh 1608 kWh £639 £161 £799 £10,238 12.8 yrs £5,750
5 kW 5024 kWh 3015 kWh 2010 kWh £798 £201 £999 £12,273 12.3 yrs £7,713
6 kW 6029 kWh 3618 kWh 2412 kWh £958 £241 £1,199 £14,307 11.9 yrs £9,675
7 kW 7034 kWh 4220 kWh 2814 kWh £1,118 £281 £1,399 £16,342 11.7 yrs £11,638
8 kW 8039 kWh 4823 kWh 3216 kWh £1,277 £322 £1,599 £18,376 11.5 yrs £13,600

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: £1,082, Upfront: £13,673, Break-even: 12.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2010 kWh 1407 kWh 603 kWh £373 £60 £433 £7,569 17.5 yrs £1,087
3 kW 3015 kWh 2110 kWh 904 kWh £559 £90 £649 £9,604 14.8 yrs £3,381
4 kW 4020 kWh 2814 kWh 1206 kWh £745 £121 £866 £11,638 13.4 yrs £5,675
5 kW 5024 kWh 3517 kWh 1507 kWh £931 £151 £1,082 £13,673 12.6 yrs £7,969
6 kW 6029 kWh 4220 kWh 1809 kWh £1,118 £181 £1,298 £15,707 12.1 yrs £10,262
7 kW 7034 kWh 4924 kWh 2110 kWh £1,304 £211 £1,515 £17,742 11.7 yrs £12,556
8 kW 8039 kWh 5627 kWh 2412 kWh £1,490 £241 £1,731 £19,776 11.4 yrs £14,850

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: £1,107, Upfront: £15,423, Break-even: 13.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2010 kWh 1467 kWh 543 kWh £388 £54 £443 £9,319 21.0 yrs £-464
3 kW 3015 kWh 2201 kWh 814 kWh £583 £81 £664 £11,354 17.1 yrs £1,929
4 kW 4020 kWh 2934 kWh 1085 kWh £777 £109 £886 £13,388 15.1 yrs £4,322
5 kW 5024 kWh 3668 kWh 1357 kWh £971 £136 £1,107 £15,423 13.9 yrs £6,715
6 kW 6029 kWh 4401 kWh 1628 kWh £1,165 £163 £1,328 £17,457 13.1 yrs £9,108
7 kW 7034 kWh 5135 kWh 1899 kWh £1,360 £190 £1,550 £19,492 12.6 yrs £11,502
8 kW 8039 kWh 5868 kWh 2171 kWh £1,554 £217 £1,771 £21,526 12.2 yrs £13,895

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: £1,123, 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 2010 kWh 1507 kWh 502 kWh £399 £50 £449 £11,069 24.6 yrs £-2,081
3 kW 3015 kWh 2261 kWh 754 kWh £599 £75 £674 £13,104 19.4 yrs £378
4 kW 4020 kWh 3015 kWh 1005 kWh £798 £100 £899 £15,138 16.8 yrs £2,837
5 kW 5024 kWh 3768 kWh 1256 kWh £998 £126 £1,123 £17,173 15.3 yrs £5,297
6 kW 6029 kWh 4522 kWh 1507 kWh £1,197 £151 £1,348 £19,207 14.2 yrs £7,756
7 kW 7034 kWh 5276 kWh 1759 kWh £1,397 £176 £1,573 £21,242 13.5 yrs £10,215
8 kW 8039 kWh 6029 kWh 2010 kWh £1,597 £201 £1,798 £23,276 12.9 yrs £12,675

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: £1,140, Upfront: £19,623, Break-even: 17.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 2010 kWh 1548 kWh 462 kWh £410 £46 £456 £13,519 29.6 yrs £-4,399
3 kW 3015 kWh 2321 kWh 693 kWh £615 £69 £684 £15,554 22.7 yrs £-1,873
4 kW 4020 kWh 3095 kWh 924 kWh £820 £92 £912 £17,588 19.3 yrs £652
5 kW 5024 kWh 3869 kWh 1156 kWh £1,024 £116 £1,140 £19,623 17.2 yrs £3,178
6 kW 6029 kWh 4643 kWh 1387 kWh £1,229 £139 £1,368 £21,657 15.8 yrs £5,703
7 kW 7034 kWh 5416 kWh 1618 kWh £1,434 £162 £1,596 £23,692 14.8 yrs £8,229
8 kW 8039 kWh 6190 kWh 1849 kWh £1,639 £185 £1,824 £25,726 14.1 yrs £10,754

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 SP11

Figures below are tailored to SP11 — click through for full league tables.

Big-Roof Britain Rank #782 of 2182
5.3 kWp (UK avg 5.1 kWp)
~11 panels (≈430 W)
Solar Payback Index Rank #738 of 2997
10.6 years (UK avg 11.3 years)
~£958 /yr • £10,173 upfront
Standing-Charge Drag Rank #720 of 2997
17.0% (UK avg 21.7%) drag on savings
£163 fixed • ~£958 /yr value

Your Area at a Glance

Your Electricity Rate
26.48p/kWh
Daily Fixed Charge
44.62p/day
Local Sunshine
1005kWh/kW
A 1 kW system generates ~1005 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: 75% • Flats: 13% • Bungalows: 11% Based on 11,159 properties

Coverage

Test Valley (75%)|Wiltshire (17%)|Basingstoke and Deane (7%)

Areas Covered

Anna, Bourne Valley, Ludgershall North & Rural, Tidworth East & Ludgershall South, Andover Romans, Evingar, Bellinger, Andover Downlands + 4 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

SP10 (Test Valley)
≈2.5 km away
Local sunshine: ~1,011 kWh/kWp · +1% vs SP11
SP9 (Wiltshire)
≈11.2 km away
Local sunshine: ~1,016 kWh/kWp · +1% vs SP11
RG28 (Basingstoke and Deane)
≈11.8 km away
Local sunshine: ~1,003 kWh/kWp · -0% vs SP11
SO20 (Test Valley)
≈12.2 km away
Local sunshine: ~1,019 kWh/kWp · +1% vs SP11
RG15 (Basingstoke and Deane)
≈18.2 km away
Local sunshine: ~994 kWh/kWp · -1% vs SP11
SP4 (Wiltshire)
≈19.3 km away
Local sunshine: ~1,018 kWh/kWp · +1% vs SP11

Similar sunshine across the UK

SA13 (Neath Port Talbot)
~1,005 kWh/kWp · -0% vs SP11
E12 (Newham)
~1,005 kWh/kWp · +0% vs SP11
E7 (Newham)
~1,005 kWh/kWp · +0% vs SP11