Northern Ireland Solar Tracker: 4,359 kWh Across 15 Weeks

Solar Today has now been tracking solar generation across seven Northern Ireland towns for 15 weeks. In that time a typical 4kW system has produced 4,359 kWh of electricity, with a 6kW system producing 6,539 kWh. At current Power NI tariffs, that is around £1,460 of value sitting on a Northern Irish roof.

Last week added another 89 kWh to the Belfast tally, with 51 hours of sunshine spread across one brilliant Wednesday and a wet Saturday. The week ended down on the previous one because cloud cover crept back in for the weekend.

The point of running the counter is to settle the question that still hangs over solar in Northern Ireland: does it really work this far north. Fifteen weeks of data say yes, with caveats worth being honest about.

Last Week, Day By Day

Here is how the week looked in Belfast, day by day, as a benchmark for any NI roof.

Day	Weather	4kW kWh	4kW value	6kW kWh	6kW value
Mon 27 Apr	Mixed	6.3	£2.13	9.5	£3.19
Tue 28 Apr	Bright	13.1	£4.40	19.7	£6.60
Wed 29 Apr	Brilliant	20.7	£6.93	31.0	£10.39
Thu 30 Apr	Brilliant	20.4	£6.84	30.6	£10.26
Fri 1 May	Bright	13.2	£4.42	19.8	£6.63
Sat 2 May	Mixed	8.4	£2.82	12.6	£4.23
Sun 3 May	Mixed	6.6	£2.22	10.0	£3.34
Total		88.7	£29.76	133.2	£44.64

What 15 weeks of NI data actually shows

The headline number is 4,359 kWh of generation tracked on a 4kW system across Belfast, Lisburn, Derry, Newry, Armagh, Ballymena, and Enniskillen. On a 6kW system the cumulative total reaches 6,539 kWh. The seven towns sit within a fairly narrow band, which is itself useful to know. Lisburn led last week with 94 kWh, Enniskillen trailed with 82 kWh, and the rest landed within ten kilowatt hours of each other. Geography matters in Northern Ireland, but not as much as the weather on any given Tuesday.

What the cumulative figure does well is collapse a lot of daily noise into something solid. Any single day in NI can swing from a 6 kWh write-off to a 20 kWh standout. Looking only at one bright Wednesday makes solar look brilliant, and looking only at a wet Sunday makes it look pointless. Fifteen weeks of running totals work out at roughly 290 kWh per week across the seven towns combined, weighted heavily by the dark stretch from late January into February. As more spring and summer weeks land in the sample, the weekly average will keep climbing. You can watch it tick over in real time on the Solar Today dashboard, refreshed daily with local weather data.

What that means for a roof in your postcode

The cumulative number is interesting, but the more honest question is what your specific roof would do. A 4kW south-facing array in Belfast at a standard pitch sits roughly in the middle of the seven towns we track. If your home is in Lisburn or Newry you would see a touch more, in Derry or Enniskillen a touch less. East-west splits sacrifice roughly 10 to 15 percent of peak generation in exchange for a smoother daily curve, which often suits a household using electricity steadily through the day rather than only in the evenings.

The solar calculator takes your postcode, system size, and rough annual electricity use, and gives an estimate of bill savings and payback period grounded in the same weather and tariff data that feeds the weekly tracker. It will also show how an export tariff or a home battery changes the picture.

The question most NI homeowners actually want answered is whether the maths makes sense for them today, given current panel prices and Power NI rates. That is a longer conversation, and we have written it up in detail in are solar panels worth it in Northern Ireland, with the latest payback figures and the trade-offs people tend to forget about until year three.

How Solar Today Works

Each morning, Solar Today pulls weather data for seven NI towns from Open-Meteo. We model what a typical 4kW and 6kW solar installation would produce that day, applying a 0.78 performance ratio to account for inverter losses, panel temperature, and soiling. Today’s value is a forecast. Once the day closes, it firms up to the observed weather.

The seven towns we currently cover are Belfast, Derry, Armagh, Newry, Enniskillen, Lisburn, and Ballymena. Each gets its own daily estimate based on local cloud cover and irradiance.

A few honest caveats:

• These are modelled estimates, not live readings from physical systems.
• Forecast days update as the weather firms up.
• Your actual generation will vary by roof orientation, system size, panel age, and any shading.

The point is not to replace your inverter app. It is to give NI homeowners a fair, locally relevant benchmark that did not exist anywhere else.

See Your Town

Visit Solar Today to see the latest week for your nearest NI town. We update it every morning, and we publish a recap like this one each Monday.

If you do not have solar yet and this week’s numbers got you curious, our solar savings calculator will give you a personal estimate based on your own home, roof, and current bill.