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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in BT26 (Lisburn and Castlereagh)

See if solar pays off for you in Lisburn and Castlereagh — 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
38.1 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£320
What you save every year
Profit Over 25 Years
£-4,207
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 Northern Ireland, the current unit rate is 0.00p/kWh with a 0.00p/day standing charge. Your postcode’s south-facing sunshine yield is 889 kWh/kW — 102 below the regional median (991).

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 889 kWh per year on a south-facing roof. We value self-used electricity at 0.0p and exported surplus at a baseline 10p via SEG. Use the calculator above for your exact tariff.

Unit rate
0.0p/kWh
Standing charge
0.0p/day
Sunshine yield (south)
889 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: £267, Upfront: £10,173, Break-even: 38.1 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1778 kWh 711 kWh 1067 kWh £0 £107 £107 £4,069 38.1 yrs £-1,936
3 kW 2667 kWh 1067 kWh 1600 kWh £0 £160 £160 £6,104 38.1 yrs £-2,903
4 kW 3556 kWh 1422 kWh 2133 kWh £0 £213 £213 £8,138 38.1 yrs £-3,871
5 kW 4445 kWh 1778 kWh 2667 kWh £0 £267 £267 £10,173 38.1 yrs £-4,839
6 kW 5334 kWh 2133 kWh 3200 kWh £0 £320 £320 £12,207 38.1 yrs £-5,807
7 kW 6222 kWh 2489 kWh 3733 kWh £0 £373 £373 £14,242 38.1 yrs £-6,775
8 kW 7111 kWh 2845 kWh 4267 kWh £0 £427 £427 £16,276 38.1 yrs £-7,742

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: £178, Upfront: £12,273, Break-even: 69.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1778 kWh 1067 kWh 711 kWh £0 £71 £71 £6,169 86.7 yrs £-4,747
3 kW 2667 kWh 1600 kWh 1067 kWh £0 £107 £107 £8,204 76.9 yrs £-6,070
4 kW 3556 kWh 2133 kWh 1422 kWh £0 £142 £142 £10,238 72.0 yrs £-7,393
5 kW 4445 kWh 2667 kWh 1778 kWh £0 £178 £178 £12,273 69.0 yrs £-8,717
6 kW 5334 kWh 3200 kWh 2133 kWh £0 £213 £213 £14,307 67.1 yrs £-10,040
7 kW 6222 kWh 3733 kWh 2489 kWh £0 £249 £249 £16,342 65.7 yrs £-11,364
8 kW 7111 kWh 4267 kWh 2845 kWh £0 £284 £284 £18,376 64.6 yrs £-12,687

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: £133, Upfront: £13,673, Break-even: 102.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1778 kWh 1244 kWh 533 kWh £0 £53 £53 £7,569 141.9 yrs £-6,502
3 kW 2667 kWh 1867 kWh 800 kWh £0 £80 £80 £9,604 120.0 yrs £-8,003
4 kW 3556 kWh 2489 kWh 1067 kWh £0 £107 £107 £11,638 109.1 yrs £-9,505
5 kW 4445 kWh 3111 kWh 1333 kWh £0 £133 £133 £13,673 102.5 yrs £-11,006
6 kW 5334 kWh 3733 kWh 1600 kWh £0 £160 £160 £15,707 98.2 yrs £-12,507
7 kW 6222 kWh 4356 kWh 1867 kWh £0 £187 £187 £17,742 95.0 yrs £-14,008
8 kW 7111 kWh 4978 kWh 2133 kWh £0 £213 £213 £19,776 92.7 yrs £-15,509

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: £120, Upfront: £15,423, Break-even: 128.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1778 kWh 1298 kWh 480 kWh £0 £48 £48 £9,319 194.1 yrs £-8,359
3 kW 2667 kWh 1947 kWh 720 kWh £0 £72 £72 £11,354 157.7 yrs £-9,913
4 kW 3556 kWh 2596 kWh 960 kWh £0 £96 £96 £13,388 139.5 yrs £-11,468
5 kW 4445 kWh 3245 kWh 1200 kWh £0 £120 £120 £15,423 128.5 yrs £-13,022
6 kW 5334 kWh 3893 kWh 1440 kWh £0 £144 £144 £17,457 121.2 yrs £-14,577
7 kW 6222 kWh 4542 kWh 1680 kWh £0 £168 £168 £19,492 116.0 yrs £-16,131
8 kW 7111 kWh 5191 kWh 1920 kWh £0 £192 £192 £21,526 112.1 yrs £-17,686

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: £111, Upfront: £17,173, Break-even: 154.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1778 kWh 1333 kWh 444 kWh £0 £44 £44 £11,069 249.0 yrs £-10,180
3 kW 2667 kWh 2000 kWh 667 kWh £0 £67 £67 £13,104 196.5 yrs £-11,770
4 kW 3556 kWh 2667 kWh 889 kWh £0 £89 £89 £15,138 170.3 yrs £-13,360
5 kW 4445 kWh 3333 kWh 1111 kWh £0 £111 £111 £17,173 154.5 yrs £-14,950
6 kW 5334 kWh 4000 kWh 1333 kWh £0 £133 £133 £19,207 144.0 yrs £-16,540
7 kW 6222 kWh 4667 kWh 1556 kWh £0 £156 £156 £21,242 136.5 yrs £-18,130
8 kW 7111 kWh 5334 kWh 1778 kWh £0 £178 £178 £23,276 130.9 yrs £-19,720

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: £102, Upfront: £19,623, Break-even: 192.0 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1778 kWh 1369 kWh 409 kWh £0 £41 £41 £13,519 330.6 yrs £-12,701
3 kW 2667 kWh 2053 kWh 613 kWh £0 £61 £61 £15,554 253.6 yrs £-14,327
4 kW 3556 kWh 2738 kWh 818 kWh £0 £82 £82 £17,588 215.1 yrs £-15,952
5 kW 4445 kWh 3422 kWh 1022 kWh £0 £102 £102 £19,623 192.0 yrs £-17,578
6 kW 5334 kWh 4107 kWh 1227 kWh £0 £123 £123 £21,657 176.5 yrs £-19,204
7 kW 6222 kWh 4791 kWh 1431 kWh £0 £143 £143 £23,692 165.5 yrs £-20,829
8 kW 7111 kWh 5476 kWh 1636 kWh £0 £164 £164 £25,726 157.3 yrs £-22,455

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.

Your Area at a Glance

Your Electricity Rate
0.00p/kWh
Daily Fixed Charge
0.00p/day
Local Sunshine
889kWh/kW
A 1 kW system generates ~889 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

No EPC data available for this outcode

Coverage

Lisburn and Castlereagh (100%)

Areas Covered

Hillsborough, Maze, Dromara, Ballymacbrennan, Ravernet, Lagan

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 Northern Ireland

BT27 (Lisburn and Castlereagh)
≈6.2 km away
Local sunshine: ~894 kWh/kWp · +1% vs BT26
BT28 (Lisburn and Castlereagh)
≈6.3 km away
Local sunshine: ~895 kWh/kWp · +1% vs BT26
BT25 (Armagh City, Banbridge and Craigavon)
≈7.4 km away
Local sunshine: ~886 kWh/kWp · -0% vs BT26
BT17 (Belfast)
≈10.8 km away
Local sunshine: ~886 kWh/kWp · -0% vs BT26
BT67 (Armagh City, Banbridge and Craigavon)
≈12.4 km away
Local sunshine: ~890 kWh/kWp · +0% vs BT26
BT10 (Belfast)
≈12.4 km away
Local sunshine: ~884 kWh/kWp · -1% vs BT26

Similar sunshine across the UK

BD21 (Bradford)
~889 kWh/kWp · +0% vs BT26
KA9 (South Ayrshire)
~889 kWh/kWp · +0% vs BT26
TS9 (North Yorkshire)
~889 kWh/kWp · +0% vs BT26