Sign 1: screw-in fuses
Can you still see porcelain fuses that screw in? Then your unit is at least forty years old. There's usually no RCD on every circuit, which you won't find in a modern installation any more.
Signs 2 and 3: tripping and heat
Does the RCD trip more than once a month, or does the unit feel warm? Have it checked. Heat often means a loose connection, and that can start to smoulder.
Sign 4: you want to connect more
An induction hob, a heat pump, solar panels or a charging point. Old units don't have room for them. Replacing is then often cheaper than adding on forever.
And when not?
If your unit already has RCBOs and you only need one extra circuit. Then extending it is enough, and we'll tell you so.
