Are Honeywell thermostats compatible with all heating systems?

Honeywell sells thermostats that work with almost all types of popular central heating systems, although homeowners using obscure types of heating systems might need special-made thermostats, often from the manufacturer. They also have thermostats for heat pumps, which require extra features.

Honeywell offers both programmable and standard thermostats, and they sell both types in models capable of working with heat pumps. While heat pumps can generally work with standard thermostats, they also have an "emergency heating" mode for times when the heat pump can't keep up with the temperature outside. This mode uses inefficient electrical-resistance heating, which is expensive to use.