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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in BT16 (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
36.7 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£333
What you save every year
Profit Over 25 Years
£-3,892
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 924 kWh/kW — 67 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 924 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)
924 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: £277, Upfront: £10,173, Break-even: 36.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1848 kWh 739 kWh 1109 kWh £0 £111 £111 £4,069 36.7 yrs £-1,852
3 kW 2772 kWh 1109 kWh 1663 kWh £0 £166 £166 £6,104 36.7 yrs £-2,777
4 kW 3696 kWh 1478 kWh 2217 kWh £0 £222 £222 £8,138 36.7 yrs £-3,703
5 kW 4620 kWh 1848 kWh 2772 kWh £0 £277 £277 £10,173 36.7 yrs £-4,629
6 kW 5544 kWh 2217 kWh 3326 kWh £0 £333 £333 £12,207 36.7 yrs £-5,555
7 kW 6467 kWh 2587 kWh 3880 kWh £0 £388 £388 £14,242 36.7 yrs £-6,481
8 kW 7391 kWh 2957 kWh 4435 kWh £0 £443 £443 £16,276 36.7 yrs £-7,406

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: £185, Upfront: £12,273, Break-even: 66.4 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1848 kWh 1109 kWh 739 kWh £0 £74 £74 £6,169 83.5 yrs £-4,691
3 kW 2772 kWh 1663 kWh 1109 kWh £0 £111 £111 £8,204 74.0 yrs £-5,986
4 kW 3696 kWh 2217 kWh 1478 kWh £0 £148 £148 £10,238 69.3 yrs £-7,281
5 kW 4620 kWh 2772 kWh 1848 kWh £0 £185 £185 £12,273 66.4 yrs £-8,577
6 kW 5544 kWh 3326 kWh 2217 kWh £0 £222 £222 £14,307 64.5 yrs £-9,872
7 kW 6467 kWh 3880 kWh 2587 kWh £0 £259 £259 £16,342 63.2 yrs £-11,168
8 kW 7391 kWh 4435 kWh 2957 kWh £0 £296 £296 £18,376 62.2 yrs £-12,463

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: £139, Upfront: £13,673, Break-even: 98.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1848 kWh 1293 kWh 554 kWh £0 £55 £55 £7,569 136.5 yrs £-6,460
3 kW 2772 kWh 1940 kWh 832 kWh £0 £83 £83 £9,604 115.5 yrs £-7,940
4 kW 3696 kWh 2587 kWh 1109 kWh £0 £111 £111 £11,638 105.0 yrs £-9,421
5 kW 4620 kWh 3234 kWh 1386 kWh £0 £139 £139 £13,673 98.7 yrs £-10,901
6 kW 5544 kWh 3880 kWh 1663 kWh £0 £166 £166 £15,707 94.4 yrs £-12,381
7 kW 6467 kWh 4527 kWh 1940 kWh £0 £194 £194 £17,742 91.4 yrs £-13,861
8 kW 7391 kWh 5174 kWh 2217 kWh £0 £222 £222 £19,776 89.2 yrs £-15,341

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: £125, Upfront: £15,423, Break-even: 123.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1848 kWh 1349 kWh 499 kWh £0 £50 £50 £9,319 186.8 yrs £-8,321
3 kW 2772 kWh 2023 kWh 748 kWh £0 £75 £75 £11,354 151.7 yrs £-9,857
4 kW 3696 kWh 2698 kWh 998 kWh £0 £100 £100 £13,388 134.2 yrs £-11,392
5 kW 4620 kWh 3372 kWh 1247 kWh £0 £125 £125 £15,423 123.6 yrs £-12,928
6 kW 5544 kWh 4047 kWh 1497 kWh £0 £150 £150 £17,457 116.6 yrs £-14,464
7 kW 6467 kWh 4721 kWh 1746 kWh £0 £175 £175 £19,492 111.6 yrs £-15,999
8 kW 7391 kWh 5396 kWh 1996 kWh £0 £200 £200 £21,526 107.9 yrs £-17,535

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: £115, Upfront: £17,173, Break-even: 148.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1848 kWh 1386 kWh 462 kWh £0 £46 £46 £11,069 239.6 yrs £-10,145
3 kW 2772 kWh 2079 kWh 693 kWh £0 £69 £69 £13,104 189.1 yrs £-11,718
4 kW 3696 kWh 2772 kWh 924 kWh £0 £92 £92 £15,138 163.8 yrs £-13,290
5 kW 4620 kWh 3465 kWh 1155 kWh £0 £115 £115 £17,173 148.7 yrs £-14,863
6 kW 5544 kWh 4158 kWh 1386 kWh £0 £139 £139 £19,207 138.6 yrs £-16,435
7 kW 6467 kWh 4851 kWh 1617 kWh £0 £162 £162 £21,242 131.4 yrs £-18,008
8 kW 7391 kWh 5544 kWh 1848 kWh £0 £185 £185 £23,276 126.0 yrs £-19,580

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: £106, Upfront: £19,623, Break-even: 184.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1848 kWh 1423 kWh 425 kWh £0 £43 £43 £13,519 318.1 yrs £-12,669
3 kW 2772 kWh 2134 kWh 638 kWh £0 £64 £64 £15,554 244.0 yrs £-14,279
4 kW 3696 kWh 2846 kWh 850 kWh £0 £85 £85 £17,588 206.9 yrs £-15,888
5 kW 4620 kWh 3557 kWh 1063 kWh £0 £106 £106 £19,623 184.7 yrs £-17,498
6 kW 5544 kWh 4269 kWh 1275 kWh £0 £128 £128 £21,657 169.9 yrs £-19,107
7 kW 6467 kWh 4980 kWh 1488 kWh £0 £149 £149 £23,692 159.3 yrs £-20,717
8 kW 7391 kWh 5691 kWh 1700 kWh £0 £170 £170 £25,726 151.3 yrs £-22,326

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
924kWh/kW
A 1 kW system generates ~924 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 (98%)|Ards and North Down (2%)|Belfast (1%)

Areas Covered

Carrowreagh, Graham's Bridge, Enler, Dundonald, Ballyhanwood, Cultra, Stormont, Scrabo + 2 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 Northern Ireland

BT4 (Belfast)
≈4.7 km away
Local sunshine: ~892 kWh/kWp · -3% vs BT16
BT5 (Belfast)
≈5.2 km away
Local sunshine: ~892 kWh/kWp · -3% vs BT16
BT18 (Ards and North Down)
≈5.9 km away
Local sunshine: ~918 kWh/kWp · -1% vs BT16
BT23 (Ards and North Down)
≈6.6 km away
Local sunshine: ~902 kWh/kWp · -2% vs BT16
BT6 (Belfast)
≈6.7 km away
Local sunshine: ~892 kWh/kWp · -3% vs BT16
BT3 (Belfast)
≈7.9 km away
Local sunshine: ~885 kWh/kWp · -4% vs BT16

Similar sunshine across the UK

LL16 (Denbighshire)
~924 kWh/kWp · +0% vs BT16
DY5 (Dudley)
~924 kWh/kWp · +0% vs BT16
S14 (Sheffield)
~924 kWh/kWp · -0% vs BT16