Examine your thermostat. If it has a setting for auxiliary or emergency heat, your system is almost certainly a heat pump system.
Auxiliary heat is activated when the main heat pump cannot supply enough heat energy to meet the demand, typically when outside temperatures are below freezing.
Locate any interior components to your heating system.
Heat pumps commonly have an indoor unit called a fan coil. This device serves two purposes: It accepts heat from the outdoor components, and it uses a fan to distribute the warm air through the house's duct work.
This unit also contains a heating coil, which serves as auxiliary or emergency heat. This coil will heat up and provide warm air when the heat pump is unable to supply enough warm air to heat the house.
If you find metal tubing lines routed from your fan coil to an external compressor or heat exchanger, you likely have a heat pump system.
Locate any exterior components to your heating system.
An air-to-air heat pump will have a large compressor mounted outside the house. This unit will be approximately a 2- to 3-foot cube with a large fan mounted in the middle.
If you have a geothermal heat pump, there may not be any visible outside components. These systems rely on heat exchanger pipes buried underground. There should be evidence of heat exchanger lines running from indoors to the external pipes.