Yes — a small system is still worth it, and there's a counterintuitive upside: the smaller the system, the higher your self-consumption percentage. With fewer panels you tend to use most of what you generate rather than exporting it cheaply, so a modest array can make a real dent in your bill even if the absolute generation is small. Around 4 kWp is a sensible minimum for most homes.
The caveat is payback. If your roof or budget limits you to a handful of panels and your bills are modest, the return on investment can be slow — particularly if you're adding a battery on top. If the numbers look poor because your bills are low and your roof is small, one way to improve them is to strip the system back: skip the battery, use a cheaper string inverter, and lean on self-consumption plus export. That can bring the after-grant cost down sharply and make the ROI look much healthier.
So "is 6 panels worth it?" usually comes down to: it'll save you money and you'll only ever win by having it, but match the spec to your situation. If you can fit more panels affordably, a 4–6 kWp system gives a better balance of self-use and surplus. If you genuinely can't, a small, simple, battery-free system is still a sensible buy — just don't over-spec it with a battery that won't pay back on a small array.