Size of generator required for power cut backup?

[cg360]

Whether you use it continuously, or only for an hour ot two at a time, or for 1 minute every Feb 29th, it still needs to be just as safe.

Got an Aldi near you?

I understand that - I'm just wondering what size generator I will need to run (observing all instructions re earthing etc.) power my central heating controller, pump and a few lights. Applicances will be connected solely to the gen, and there will be no house wiring/gen wiring interface.

I found that offer too - only on offer yesterday, though!