Specialist solar panels for schools in Porthmadog

School rooftop solar across Gwynedd

A one kilowatt-peak array on a shallow pitched roof in Porthmadog models at 820 kWh a year, from modelled irradiation of 1,044 kWh per square metre in the plane of the array (EU PVGIS v5.2, SARAH3, 10 degree pitch, 14 percent system loss). 7 percent below our mean puts Porthmadog at the weaker end of the range, which raises the premium on self consumption and lowers the value of anything that leaves the site.

Scaled up, a 380 kWp array, sized to what the nearest school scheme on record applied for, 68 miles away at St Helens, models at about 311,600 kWh a year before shading, and needs roughly 1,129 square metres of clear roof. We take the size from the nearest real application rather than a round number, so the example is anchored to something a planning officer has already seen.

Spread across the year that is about 78,800 kWh landing in July and August and roughly 12,200 kWh across December and January. SP Energy Networks sets what may go back onto the network here, so the July figure is the one worth putting in front of a governing body first.

What the planning record shows around Porthmadog

The Renewable Energy Planning Database holds no school scheme for Porthmadog and the area around it. Read that as a gap in the record, not a gap in the roofs: the database is reliable above one megawatt and thin below it, and a school array is typically a fifth of a megawatt.

The nearest education scheme on the record is 68 miles from Porthmadog, at St Helens: 380 kWp at The Sutton Academy, Elton Head Road, applicant Located Property Limited, which holds consent and is awaiting construction. That is someone else's application, not ours, and it is here because it shows what Merseyside planning has already accepted at an education site. Source: Renewable Energy Planning Database, Q1 2026.

The summer holiday problem for a Porthmadog school

25.3 percent of the annual output modelled for Porthmadog arrives in the two months a school uses least (EU PVGIS v5.2). Term ends in the third week of July and the buildings stay largely empty until September. May is the strongest single month here at 14.5 percent of the annual total, which is still term time, and that works slightly in your favour against towns whose curve peaks in July.

The inverse holds at the other end. December and January together return only 3.9 percent of the year, and those are the months with the heating, the lighting and the full timetable all running at once. The roof makes 8.5 times as much in May as it does in December, and August alone outproduces December by about 6.7 to one. 75 percent of the year arrives between April and September, and the point of that figure is not that the summer half goes unused, because April, May and June are full teaching months that draw hard. It is that the concentration peaks in the few weeks at the end of it when the building is shut.

Across the country the arithmetic settles at roughly 49 percent of output on a session day, against about 71 percent for a weekday business. That figure hardly varies by location, which is why the local numbers that matter here are the yield, the roofs and what has already cleared planning nearby.

Then there is the afternoon. From roughly three o'clock the building empties while the roof is still working, so a system sized on annual consumption will over-generate in exactly the hours nobody is there. We size on half hourly data for that reason.

That argues for a particular shape of scheme rather than against one. Size to the load that does not stop at the end of term, count in lettings, holiday clubs and summer works honestly rather than optimistically, and then decide whether storage or an export arrangement with SP Energy Networks pays for the surplus that is left.

We set out the complete version of the term time arithmetic on the home page, and what it does to a payback figure under costs.

Grid connection through SP Energy Networks

SP Energy Networks is the network operator here, and their answer on export capacity shapes the design. Any commercial array above 3.68 kW per phase connects under G99 rather than G98, and the application fixes what you are allowed to push back onto the network. If the local network is tight, limiting export rarely breaks the case here: most of the generation is consumed on site while the building is working.

Across Gwynedd the planning database records 19 solar schemes totalling 221 MW, of which 6 are operational (REPD Q1 2026).

Questions governors ask us about Porthmadog schools

Is there enough sun around Porthmadog for this to be worth doing?

The model gives 820 kWh a year for every kWp installed at this latitude, so a 380 kWp array comes out at roughly 311,600 kWh a year before shading. It needs about 1,129 square metres of clear roof once walkways and rooflight setbacks are allowed for. Source: EU PVGIS v5.2, SARAH3, 10 degree pitch, 14 percent system loss.

Does a Porthmadog school waste its generation in August?

25.3 percent of the modelled annual output for Porthmadog falls in July and August, when the buildings are closed for most of six weeks (EU PVGIS v5.2). It does not go to waste, but it only has three places to go: the base load that runs regardless, such as servers, catering refrigeration and ventilation; storage; or export under an agreement with SP Energy Networks. We model all three against your half hourly data before an array is sized.

Will the network around Porthmadog accept the export?

SP Energy Networks is the distribution network operator for Gwynedd. Anything above 3.68 kW per phase connects under G99, and the application fixes the export limit. On a school site the incoming supply is often the binding constraint rather than the roof, so we ask that question before anyone sizes an array.