Six Months of NI Solar Data: What 11,652 kWh Tells You

Solar Today has now been running for 26 weeks, half a year of daily generation estimates for seven towns across Northern Ireland. In that time the running total has passed 11,652 kWh for a typical 4kW system, worth about £3,900 at current tariffs, with the 6kW benchmark modelled at 17,479 kWh.

Numbers like that change the conversation. One good week can be dismissed as luck, and one grey week as proof that panels do not belong here. Twenty-six weeks of data, taken through a Northern Irish winter, spring and early summer, is much harder to argue with.

The week just gone kept the total climbing at pace, too. A Belfast 4kW system added 137.4 kWh, nudging past even the late June heatwave week.

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 6 Jul	Brilliant	17.4	£5.83	26.1	£8.74
Tue 7 Jul	Brilliant	16.2	£5.42	24.3	£8.14
Wed 8 Jul	Brilliant	22.5	£7.54	33.8	£11.31
Thu 9 Jul	Brilliant	19.6	£6.57	29.4	£9.86
Fri 10 Jul	Brilliant	20.7	£6.92	31.0	£10.38
Sat 11 Jul	Brilliant	18.1	£6.08	27.2	£9.12
Sun 12 Jul	Brilliant	22.9	£7.67	34.3	£11.51
Total		137.4	£46.03	206.1	£69.06

Half a Year of Watching NI Roofs

Twenty-six weeks is long enough to capture Northern Ireland at its worst and its best. The tracker launched in the depths of winter, ran through storm season and the short grey days, and has now banked a full spring and early summer. Add the seven towns together and a standard 4kW system logged 11,652 kWh of modelled generation in that time, worth roughly £3,903 at current Power NI rates. The larger 6kW benchmark reached 17,479 kWh.

Spread that across the towns and the average roof produced about 1,665 kWh in six months, most of it arriving since March. That is the shape of solar in this part of the world: a quiet winter, a fast ramp through spring, and a summer that does the heavy lifting. It is also why the question we hear most, whether solar works in Northern Ireland at all, feels increasingly settled. Our guide on whether solar panels are worth it walks through the full-year maths behind that answer.

The Week That Kept the Total Climbing

The seven days to Sunday 12 July were among the strongest we have logged. A Belfast 4kW system produced 137.4 kWh, worth £46.03, edging past even the late June heatwave week. The 6kW benchmark made 206.1 kWh, or £69.06. Every day of the week rated brilliant on our scale, from 16.2 kWh on the quietest day to 22.9 kWh on Sunday, and Belfast collected 89.3 hours of sunshine along the way.

The rest of the region kept pace. Newry led with 140.2 kWh and 95.5 hours of sunshine, Armagh and Lisburn matched Belfast almost exactly, and Derry, under 82% average cloud, still cleared 112 kWh. The week finished 121% up on the dull first week of July, a reminder of how quickly the totals move at this time of year. The daily figures for each town are on Solar Today, updated every morning.

From Our Benchmark to Your Roof

A tracker like this is a benchmark, not a promise. The figures are modelled from local weather data for a typical, well-sited system, and your own roof will bend the numbers up or down depending on its direction, pitch, shading and the size of the array you fit. The value of six months of data is the pattern it proves: output arrives steadily, through cloud and heatwave alike, and it compounds. If the running total has you wondering what your own half-year figure would look like, the solar savings calculator turns your roof, system size and current bill into a personal estimate in a couple of minutes.

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.