The most common question we get, and the honest answer: yes, but not for the reason most sales pitches give.
It is the first thing nearly everyone asks, usually with some scepticism, and it deserves a straight answer rather than a brochure one.
Panels run on daylight, not heat. They generate whenever there is light, and they generate less on a heavily overcast day than a clear one, but they do not stop. Panels are also more efficient at lower temperatures, which is why a bright cold day in March can outperform a hazy warm one in July.
Ireland gets less sun than Spain and more than people assume. The relevant comparison is not the Mediterranean, it is Germany, which has broadly similar irradiance and one of the largest installed solar bases in the world. Nobody argues that solar does not work in Germany.
The seasonality is real and worth planning for. Generation is heavily weighted to summer. A system that covers most of your daytime usage in June will cover a fraction of it in December. That is normal, it is priced into any honest estimate, and it is why solar reduces a bill rather than eliminating one.
What actually limits an Irish roof. In our experience it is rarely the weather. It is shading from a chimney, a dormer, a roof window or a neighbouring tree, and it is orientation. A shaded south-facing roof can perform worse than a clear east-west one, which is why the survey looks at obstructions before it looks at square metres.