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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in BT27 (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
37.9 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£322
What you save every year
Profit Over 25 Years
£-4,158
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 894 kWh/kW — 96 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 894 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)
894 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: £268, Upfront: £10,173, Break-even: 37.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1789 kWh 715 kWh 1073 kWh £0 £107 £107 £4,069 37.9 yrs £-1,923
3 kW 2683 kWh 1073 kWh 1610 kWh £0 £161 £161 £6,104 37.9 yrs £-2,884
4 kW 3577 kWh 1431 kWh 2146 kWh £0 £215 £215 £8,138 37.9 yrs £-3,845
5 kW 4472 kWh 1789 kWh 2683 kWh £0 £268 £268 £10,173 37.9 yrs £-4,806
6 kW 5366 kWh 2146 kWh 3220 kWh £0 £322 £322 £12,207 37.9 yrs £-5,768
7 kW 6261 kWh 2504 kWh 3756 kWh £0 £376 £376 £14,242 37.9 yrs £-6,729
8 kW 7155 kWh 2862 kWh 4293 kWh £0 £429 £429 £16,276 37.9 yrs £-7,690

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: £179, Upfront: £12,273, Break-even: 68.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1789 kWh 1073 kWh 715 kWh £0 £72 £72 £6,169 86.2 yrs £-4,738
3 kW 2683 kWh 1610 kWh 1073 kWh £0 £107 £107 £8,204 76.4 yrs £-6,057
4 kW 3577 kWh 2146 kWh 1431 kWh £0 £143 £143 £10,238 71.5 yrs £-7,376
5 kW 4472 kWh 2683 kWh 1789 kWh £0 £179 £179 £12,273 68.6 yrs £-8,695
6 kW 5366 kWh 3220 kWh 2146 kWh £0 £215 £215 £14,307 66.7 yrs £-10,014
7 kW 6261 kWh 3756 kWh 2504 kWh £0 £250 £250 £16,342 65.3 yrs £-11,333
8 kW 7155 kWh 4293 kWh 2862 kWh £0 £286 £286 £18,376 64.2 yrs £-12,652

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: £134, Upfront: £13,673, Break-even: 101.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1789 kWh 1252 kWh 537 kWh £0 £54 £54 £7,569 141.0 yrs £-6,496
3 kW 2683 kWh 1878 kWh 805 kWh £0 £80 £80 £9,604 119.3 yrs £-7,994
4 kW 3577 kWh 2504 kWh 1073 kWh £0 £107 £107 £11,638 108.4 yrs £-9,492
5 kW 4472 kWh 3130 kWh 1342 kWh £0 £134 £134 £13,673 101.9 yrs £-10,989
6 kW 5366 kWh 3756 kWh 1610 kWh £0 £161 £161 £15,707 97.6 yrs £-12,487
7 kW 6261 kWh 4382 kWh 1878 kWh £0 £188 £188 £17,742 94.5 yrs £-13,985
8 kW 7155 kWh 5008 kWh 2146 kWh £0 £215 £215 £19,776 92.1 yrs £-15,483

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: £121, Upfront: £15,423, Break-even: 127.7 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1789 kWh 1306 kWh 483 kWh £0 £48 £48 £9,319 193.0 yrs £-8,353
3 kW 2683 kWh 1959 kWh 724 kWh £0 £72 £72 £11,354 156.7 yrs £-9,905
4 kW 3577 kWh 2612 kWh 966 kWh £0 £97 £97 £13,388 138.6 yrs £-11,456
5 kW 4472 kWh 3264 kWh 1207 kWh £0 £121 £121 £15,423 127.7 yrs £-13,008
6 kW 5366 kWh 3917 kWh 1449 kWh £0 £145 £145 £17,457 120.5 yrs £-14,559
7 kW 6261 kWh 4570 kWh 1690 kWh £0 £169 £169 £19,492 115.3 yrs £-16,111
8 kW 7155 kWh 5223 kWh 1932 kWh £0 £193 £193 £21,526 111.4 yrs £-17,662

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: £112, Upfront: £17,173, Break-even: 153.6 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1789 kWh 1342 kWh 447 kWh £0 £45 £45 £11,069 247.5 yrs £-10,175
3 kW 2683 kWh 2012 kWh 671 kWh £0 £67 £67 £13,104 195.3 yrs £-11,762
4 kW 3577 kWh 2683 kWh 894 kWh £0 £89 £89 £15,138 169.3 yrs £-13,349
5 kW 4472 kWh 3354 kWh 1118 kWh £0 £112 £112 £17,173 153.6 yrs £-14,937
6 kW 5366 kWh 4025 kWh 1342 kWh £0 £134 £134 £19,207 143.2 yrs £-16,524
7 kW 6261 kWh 4695 kWh 1565 kWh £0 £157 £157 £21,242 135.7 yrs £-18,111
8 kW 7155 kWh 5366 kWh 1789 kWh £0 £179 £179 £23,276 130.1 yrs £-19,699

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: £103, Upfront: £19,623, Break-even: 190.8 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1789 kWh 1377 kWh 411 kWh £0 £41 £41 £13,519 328.6 yrs £-12,696
3 kW 2683 kWh 2066 kWh 617 kWh £0 £62 £62 £15,554 252.0 yrs £-14,319
4 kW 3577 kWh 2755 kWh 823 kWh £0 £82 £82 £17,588 213.8 yrs £-15,942
5 kW 4472 kWh 3443 kWh 1029 kWh £0 £103 £103 £19,623 190.8 yrs £-17,565
6 kW 5366 kWh 4132 kWh 1234 kWh £0 £123 £123 £21,657 175.5 yrs £-19,189
7 kW 6261 kWh 4821 kWh 1440 kWh £0 £144 £144 £23,692 164.5 yrs £-20,812
8 kW 7155 kWh 5509 kWh 1646 kWh £0 £165 £165 £25,726 156.3 yrs £-22,435

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
894kWh/kW
A 1 kW system generates ~894 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

Blaris, Hilden, Hillhall, Harmony Hill, Magheralave, Ravernet, Lambeg, Drumbo + 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 Northern Ireland

BT28 (Lisburn and Castlereagh)
≈2.3 km away
Local sunshine: ~895 kWh/kWp · +0% vs BT27
BT17 (Belfast)
≈4.7 km away
Local sunshine: ~886 kWh/kWp · -1% vs BT27
BT26 (Lisburn and Castlereagh)
≈6.2 km away
Local sunshine: ~889 kWh/kWp · -1% vs BT27
BT10 (Belfast)
≈6.2 km away
Local sunshine: ~884 kWh/kWp · -1% vs BT27
BT11 (Belfast)
≈7.5 km away
Local sunshine: ~884 kWh/kWp · -1% vs BT27
BT9 (Belfast)
≈8.7 km away
Local sunshine: ~893 kWh/kWp · -0% vs BT27

Similar sunshine across the UK

M44 (Salford)
~894 kWh/kWp · +0% vs BT27
PA66 (Argyll and Bute)
~894 kWh/kWp · -0% vs BT27
CA24 (Cumberland)
~894 kWh/kWp · -0% vs BT27