Two units, one power meter.

[Collin Smith]

I have a duplex that has a single power meter for the two units. As it is now, I pay for power. One tenant apparently likes to keep it near 90 degrees in the winter (thankfully today it was 80 outside so her heater didn't have to work too hard) and I want to know how I can see how much power is going to each unit. This is an upstairs/downstairs duplex. I have been told to split the power lines between the two units so they are each metered separately would be cost prohibitive, is there an inline option that can show me the consumption? I would like to see if I can go to an option where I pay up $xx and anything over is their responsibility. The way I see it, they will certainly care more about their usage if they have to pay some. Thanks.