It’s the first thing almost everyone asks, usually with a bit of a laugh: sure, does solar even work here?
It does. There is a catch around the seasons, though, and it changes how a system should be designed, so it’s worth knowing before you get quotes.
Panels run on daylight
A lot of people think panels need direct sunshine, or warmth. They need neither.
Solar panels turn light into electricity. Direct sun on a clear day gives the highest output, but under cloud they keep generating from diffuse light (light that has been scattered on its way down). Output drops on a dull day. It doesn’t stop.
What counts is how much light lands on the roof over a year, not how warm it gets. Heat actually works slightly against panels: the cells lose efficiency as they get hotter, and every panel has a temperature coefficient that tells you by how much. A cool, bright day is close to ideal, and Ireland gets plenty of those.
The seasons are the real issue
Ireland is a long way north, so the gap between summer and winter daylight is large, far larger than in southern Europe. Summer days are long and generation is strong. In winter the days are short, the sun sits low, and generation is a fraction of the summer figure.
So a system here won’t give you a steady output all year. You get a lot in summer and comparatively little in the depths of winter. That has two practical effects.
First, solar will not wipe out a winter electricity bill. A good quote should say so and show its assumptions. What a well-designed system does is cut the electricity you buy over the year by a good margin, mostly in the brighter two-thirds of it.
Second, you need a plan for the summer surplus. In June a well-sized system may generate more in the middle of the day than the building can use. That surplus gets stored, exported or wasted.
Using the power on site is what pays
How much of the generated electricity you use on site is the biggest factor in how well a system pays in Ireland.
A unit you use is worth what you would otherwise have paid for it. A unit you export is worth your supplier’s export rate, which is a good deal less. Two identical systems on two identical roofs can give very different returns depending on when the people inside use power.
So before we look at a roof, we ask when the building uses electricity.
- A dairy farm draws heavily during daylight: parlour washing, plate cooling, water pumping. A lot of the generation gets used on site without any effort.
- A manufacturing or logistics unit running through the working day is in a similar position.
- A household where everyone leaves at eight and gets back at six is the opposite. Generation peaks while the house is empty.
For that house, a battery is often what makes the difference. It moves midday generation into the evening, so units that would have been exported replace units you’d have bought. For the farm or the unit, a battery may add much less.
Every building is different. A design that starts from your consumption is worth more than one that starts from your roof area.
Orientation and shading
People worry about two more things. One is more forgiving than they expect. The other needs proper attention at survey.
Orientation. South-facing is best, but it’s not the only option. East–west arrays are common and work well. They give a flatter curve, with peaks in the morning and evening instead of one midday spike. For a household that uses most of its electricity at the start and end of the day, that can suit better than a south-facing array, even though the annual total is lower.
Shading. This matters more than people expect, because one shaded panel can drag down every panel wired in the same string. It can be designed around: panel-level optimisers or a different string layout can recover much of the loss. What’s not acceptable is an installer ignoring shading at survey and leaving you to find out afterwards.
Chimneys, dormers, mature trees and neighbouring buildings all need to be checked on site, with the seasons in mind. The low winter sun casts far longer shadows than the summer sun.
The short answer
Solar works here if the system is sized to how you use electricity and you go in knowing that output swings a lot between summer and winter.
What doesn’t work is a system sized to fill a roof, sold on a payback figure with unstated assumptions, on a building nobody looked at properly.
If you want your own property looked at, including being told if we think it’s a poor candidate, book a free site survey or give us a call.