No, I don't think you are overreacting.

I'm curious, how many units are in your building? I'm guessing it's small, but I could be wrong.

What I'd do first is check to make sure that the switch labeled back stair well actually does control the lighting on the stairwell--because in older buildings, sometimes wiring gets re-routed, but the labels in the circuit box don't get changed. Same with the oil burner.

Then I'd contact a lawyer to see if you have grounds for suing the landlord to get back the money you've spent that you shouldn't have. Then I'd contact the landlord.

I'd wait on contacting the other tenants until you have a plan for dealing with the landlord. You don't want one of them running to tattle to the landlord before you are ready to deal with the situation.

Also google "landlord/tenant law [yourstate]" to see what the law in your area has to say about this.

Thanks camlan. I've check the switch in the electric box marked back stairwell, and it does turn off the stairwell light. There are four apartments in the building, two on the first floor and two on the second. I've noticed there are only four electric meters, when there should be five, one for each apartment and one for things outside the apartments. I live on the second floor, and the electric circuit braker box is in the back stair landing, right next to the one for the other upstairs apartment. I've taken a peak inside my neighbors box (not sure if I really should have done that, but it is in the landing we both use.) She has the septic pump wired into her box, so its not just me that's getting overbilled for electric. I've lived here for seven years, and my next door neighbor has lived here for about eleven years, so that's adding up to a lot of money.