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Big Roof Britain Solar Payback Index Standing Charge Drag

Solar Panels in BT81 (Derry City and Strabane)

See if solar pays off for you in Derry City and Strabane — 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
40.5 years
After this, it's pure profit
Upfront Cost
£12,207
What you pay to get started
Annual Benefit
£301
What you save every year
Profit Over 25 Years
£-4,676
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 837 kWh/kW — 154 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 837 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)
837 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: £251, Upfront: £10,173, Break-even: 40.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1673 kWh 669 kWh 1004 kWh £0 £100 £100 £4,069 40.5 yrs £-2,061
3 kW 2510 kWh 1004 kWh 1506 kWh £0 £151 £151 £6,104 40.5 yrs £-3,091
4 kW 3347 kWh 1339 kWh 2008 kWh £0 £201 £201 £8,138 40.5 yrs £-4,122
5 kW 4184 kWh 1673 kWh 2510 kWh £0 £251 £251 £10,173 40.5 yrs £-5,152
6 kW 5020 kWh 2008 kWh 3012 kWh £0 £301 £301 £12,207 40.5 yrs £-6,183
7 kW 5857 kWh 2343 kWh 3514 kWh £0 £351 £351 £14,242 40.5 yrs £-7,213
8 kW 6694 kWh 2678 kWh 4016 kWh £0 £402 £402 £16,276 40.5 yrs £-8,243

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: £167, Upfront: £12,273, Break-even: 73.3 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1673 kWh 1004 kWh 669 kWh £0 £67 £67 £6,169 92.2 yrs £-4,830
3 kW 2510 kWh 1506 kWh 1004 kWh £0 £100 £100 £8,204 81.7 yrs £-6,195
4 kW 3347 kWh 2008 kWh 1339 kWh £0 £134 £134 £10,238 76.5 yrs £-7,561
5 kW 4184 kWh 2510 kWh 1673 kWh £0 £167 £167 £12,273 73.3 yrs £-8,926
6 kW 5020 kWh 3012 kWh 2008 kWh £0 £201 £201 £14,307 71.2 yrs £-10,291
7 kW 5857 kWh 3514 kWh 2343 kWh £0 £234 £234 £16,342 69.8 yrs £-11,656
8 kW 6694 kWh 4016 kWh 2678 kWh £0 £268 £268 £18,376 68.6 yrs £-13,021

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: £126, Upfront: £13,673, Break-even: 108.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1673 kWh 1171 kWh 502 kWh £0 £50 £50 £7,569 150.8 yrs £-6,565
3 kW 2510 kWh 1757 kWh 753 kWh £0 £75 £75 £9,604 127.5 yrs £-8,097
4 kW 3347 kWh 2343 kWh 1004 kWh £0 £100 £100 £11,638 115.9 yrs £-9,630
5 kW 4184 kWh 2929 kWh 1255 kWh £0 £126 £126 £13,673 108.9 yrs £-11,162
6 kW 5020 kWh 3514 kWh 1506 kWh £0 £151 £151 £15,707 104.3 yrs £-12,695
7 kW 5857 kWh 4100 kWh 1757 kWh £0 £176 £176 £17,742 101.0 yrs £-14,227
8 kW 6694 kWh 4686 kWh 2008 kWh £0 £201 £201 £19,776 98.5 yrs £-15,760

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: £113, Upfront: £15,423, Break-even: 136.5 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1673 kWh 1222 kWh 452 kWh £0 £45 £45 £9,319 206.2 yrs £-8,415
3 kW 2510 kWh 1832 kWh 678 kWh £0 £68 £68 £11,354 167.5 yrs £-9,998
4 kW 3347 kWh 2443 kWh 904 kWh £0 £90 £90 £13,388 148.2 yrs £-11,581
5 kW 4184 kWh 3054 kWh 1130 kWh £0 £113 £113 £15,423 136.5 yrs £-13,163
6 kW 5020 kWh 3665 kWh 1356 kWh £0 £136 £136 £17,457 128.8 yrs £-14,746
7 kW 5857 kWh 4276 kWh 1581 kWh £0 £158 £158 £19,492 123.3 yrs £-16,329
8 kW 6694 kWh 4887 kWh 1807 kWh £0 £181 £181 £21,526 119.1 yrs £-17,911

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: £105, Upfront: £17,173, Break-even: 164.2 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1673 kWh 1255 kWh 418 kWh £0 £42 £42 £11,069 264.6 yrs £-10,232
3 kW 2510 kWh 1883 kWh 628 kWh £0 £63 £63 £13,104 208.8 yrs £-11,848
4 kW 3347 kWh 2510 kWh 837 kWh £0 £84 £84 £15,138 180.9 yrs £-13,465
5 kW 4184 kWh 3138 kWh 1046 kWh £0 £105 £105 £17,173 164.2 yrs £-15,081
6 kW 5020 kWh 3765 kWh 1255 kWh £0 £126 £126 £19,207 153.0 yrs £-16,697
7 kW 5857 kWh 4393 kWh 1464 kWh £0 £146 £146 £21,242 145.1 yrs £-18,313
8 kW 6694 kWh 5020 kWh 1673 kWh £0 £167 £167 £23,276 139.1 yrs £-19,929

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: £96, Upfront: £19,623, Break-even: 203.9 yrs
System Annual output Self-use Exported Bill saving Export income Annual benefit Upfront cost Break-even 20-year net
2 kW 1673 kWh 1289 kWh 385 kWh £0 £38 £38 £13,519 351.2 yrs £-12,749
3 kW 2510 kWh 1933 kWh 577 kWh £0 £58 £58 £15,554 269.4 yrs £-14,399
4 kW 3347 kWh 2577 kWh 770 kWh £0 £77 £77 £17,588 228.5 yrs £-16,048
5 kW 4184 kWh 3221 kWh 962 kWh £0 £96 £96 £19,623 203.9 yrs £-17,698
6 kW 5020 kWh 3866 kWh 1155 kWh £0 £115 £115 £21,657 187.6 yrs £-19,348
7 kW 5857 kWh 4510 kWh 1347 kWh £0 £135 £135 £23,692 175.9 yrs £-20,997
8 kW 6694 kWh 5154 kWh 1540 kWh £0 £154 £154 £25,726 167.1 yrs £-22,647

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
837kWh/kW
A 1 kW system generates ~837 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

Derry City and Strabane (99%)|Fermanagh and Omagh (1%)

Areas Covered

Glenderg, Castlederg, Newtownstewart, Finn, Drumquin

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

BT82 (Derry City and Strabane)
≈15.9 km away
Local sunshine: ~795 kWh/kWp · -5% vs BT81
BT78 (Fermanagh and Omagh)
≈20.6 km away
Local sunshine: ~832 kWh/kWp · -1% vs BT81
BT79 (Fermanagh and Omagh)
≈25.6 km away
Local sunshine: ~827 kWh/kWp · -1% vs BT81
BT93 (Fermanagh and Omagh)
≈28.3 km away
Local sunshine: ~829 kWh/kWp · -1% vs BT81
BT94 (Fermanagh and Omagh)
≈37.4 km away
Local sunshine: ~835 kWh/kWp · -0% vs BT81
BT48 (Derry City and Strabane)
≈37.6 km away
Local sunshine: ~827 kWh/kWp · -1% vs BT81

Similar sunshine across the UK

EH38 (Scottish Borders)
~837 kWh/kWp · -0% vs BT81
G53 (Glasgow City)
~837 kWh/kWp · +0% vs BT81
G73 (South Lanarkshire)
~837 kWh/kWp · +0% vs BT81