Honestly, it's poor — and this is one of the most important realities for newcomers to understand. Irish winters bring short days, low sun angles and a lot of cloud, so even a well-sized system generates a fraction of its summer output in December and January. The cruel irony is that this is exactly when your electricity demand is highest (heating, lights, everything on), so solar does least when you need most. A hot water diverter, for instance, will barely heat water on the darkest days because there's simply not enough surplus.
This winter weakness shapes a lot of good design decisions. It's why people deliberately oversize their panel array relative to the inverter — to squeeze a more useful output from the limited winter light, accepting some "clipping" of excess on bright summer days. It's also why load-shifting onto cheap night/EV rates matters so much in winter: when the panels can't deliver, charging a battery and heating water overnight at a low rate is how you keep costs down, rather than relying on generation that isn't there.
The practical takeaway: judge solar on the *whole year*, not on a glorious summer week. Generation in summer can be excellent and very satisfying, but you have to offset that against near-zero benefit in midwinter. Anyone promising big winter savings from panels alone is overselling. Plan for solar to carry you spring through autumn and to lean on smart tariffs, a battery, and efficient heating to get through the dark months.