I've seen several different stats saying that elevators are 2% to 10% of the total energy use of a building. If you have a building with tenants, so you're only counting common areas energy use, that percentage is going to be way way higher. I'm all the apartments I've lived they had a different circuit and energy contract for the elevator and common areas, so they could split the bill between the tenants, and the elevator energy use was quite obvious, specially in vacation sessions (summer, christmas...)

I'm sure they'll notice the change.