More than most people expect — and this is one of the most repeated clarifications among Irish solar owners. There's a common misconception that an inverter is "limited" by its kW rating, so a 5 kW inverter can only handle 5 kW of panels. In practice, inverters are limited by voltage and current per string, not by a simple kW cap, and it's normal and beneficial to oversize the panel array relative to the inverter.
What actually constrains you is the inverter's maximum string voltage and the number of MPPT inputs (strings) it has. For example, a typical hybrid inverter might accept up to ~600V DC per string; with panels around 39V open-circuit each, that sets how many panels can go in series on one string. Some inverters, paired with optimisers, are rated to handle close to double their nominal output in panels. So a 5 kW inverter can often run a 6–8 kWp array comfortably.
The reason you'd oversize is winter: more panels means a more useful output in our dull months, even if you "clip" a little excess on the brightest summer days (and a battery can capture some of that). The practical limits to check with your installer are the inverter's max string voltage, max input current per MPPT, and how many strings it supports. Don't let a salesperson talk you into a bigger, pricier inverter on the false premise that kW-of-panels must equal kW-of-inverter.