1 Furnace in 2 Tenant Duplex

[Matthew John]

Hey guys, 

I have a upper/lower Duplex that only has 1 furnace. It's setup right now so the tenants each have their own Gas bill in their name, but one of the tenant's bills is considerably higher than the others. 

The tenant in the bottom unit poorly manages the furnace, leaving it on almost at all times. He's accumulated quite a large bill because of this. 

The house was originally a SFH, but it was converted into a Duplex before I bought it. Each tenant has their own Hot Water Heater, but 1 Furnace heats the entire house. The lower unit, which controls the furnace, is around 950sqft and the upper unit is around 450sqft.

The bottom unit tenant is challenging me, demanding I reimburse him for the heat which is going towards the 2nd floor. He's withholding rent right now saying I need to cover half his bill since his heating costs are going towards the upper unit. 

I'm curious to know what's the right thing to do in this situation...

I've explained to the Bottom tenant he has the luxury of controlling the temperature of the house. The upper tenant has complained to me multiple times about it being too hot in his unit because the bottom tenant does not actively manage the thermostat. He leaves the heat on 'all the time', even when he's not home or in the warmer months of summer. 

Now the bottom tenant is withholding rent until I 'pay him half his bill' because he's paying for the upper unit's heat. 

What do you think I should do in this situation?

[Alex S.]

You can install electric baseboard heater for the 2nd unit and they will have their own heating source.