@Bin Chen I am not an HVAC professional, but in my experience every thermostat in my properties will heat the property to the set temperature.

Its gotta be a dual zone system, then the FAU actually operates as 2 separate HVAC systems. 2 thermostats etc.

All that being said, I have seen situations where tenants complained about ovens not cooking properly and it turned out to be a bad thermostat.

I use Honeywell 9000 wifi thermostats that send me alerts for humidity or temperature levels I configure.None of these items have monitoring or monthly fees.

Ring doorbell, Nest Thermostat, (I forget the brand but) smart wall plugs/light switches got A LOT of attention in our latest rental and cost very little.

The A/C people came out ( I had authorized them to do the seasonal cleaning and maintenance as well at the same time).I got the bill for the regular maintenance..but on the bill was a charge for 20.00 for battery replacement in the thermostat.

The tenants we accepted continue to pay rent online through cozy.co .The tenants that we chose have been great so far, the only complaints really being the heat situation, since there is only one thermostat(I use a nest thermostat, which I can control max and min temps) bottom tenant likes it really hot, and upstairs not so much.

If you have hot water baseboard, you could set each level on their own zone so they at least have their own thermostat.

Fall & Spring HVAC Service Target Date: April and October This service can aid in early detection of costly problems and save the cost of expensive, emergency service.A/C Service Includes: Check condenser coil, adjust operating pressures, monitor safety controls and starter capabilities, clean or replace filter, adjust blower components, calibrate thermostat, measure for proper temperature differences, clean condensate drain, tighten electrical connections, measure voltage and amperage on motors, lubricate moving parts.

@Michael Plaks BP programmers have got to allow for "reactions" that are more expressive than a vote!