God this is going to sound really petty.
We live in apartments. The conversion is rubbish. The lights in the hall I discovered during a power trip out all run on my electricity. All the flats are on pre payment meter which is more expensive anyway.
Tbh in the past this wasn't an issue much as old neighbour was respectful and immediately switched off. New neighbours frequently leave it on for hours and all weekend if we are away and don't switch it off at night.
Aibu to be miffed about paying electricity to service someone else use?