Both electromechanical and electronic thermostats work with most types of gas, oil, electric, and even hydronic heating systems, as well as with air conditioners. Most have some type of adjustment to suit the system—wires that are jumpered, a small switch on the back, or the like. This adjustment is necessary because some heating systems are much slower to heat up than others and cycle differently. And some types of heating require system fans and others don’t.
If you have a system that provides multiple stages of heating and cooling, such as a dual-speed air conditioner, a furnace with two sets of burners, or a heat pump, you need a thermostat that is designed to handle this complication. Such a thermostat may be either electromechanical or electronic and, in fact, even some conventional thermostats have a jumper or switch that can be set to modify the thermostat for such equipment.
A zoned heating system, with multiple heating or cooling zones, can be operated with electromechanical thermostats, but you can really fine-tune your home’s areas for comfort with a programmable electronic thermostat.
Most heat pumps have an auxiliary electric heating element that kicks on when the room’s temperature drops about 2 degrees lower than the thermostat’s setting (or “set point”). If the room temperature is allowed to drop to 60 degrees at night and is then turned up to 70 degrees in the morning, the auxiliary heat will come on until the room temperature reaches about 68 degrees. In most parts of the country, using this much electric heat is quite expensive.
A sophisticated electronic heat-pump thermostat, on the other hand, automatically calculates when the heat must come on to bring a room’s temperature up to the set point by the time you’ve programmed it for. It tells the heat pump to bring it up from 60 to 61 degrees, then from 61 to 62 degrees, and so forth. That way, the electric auxiliary heat is “fooled” into staying off.
