Forced Air:  Furnace has a blower that blows the heated air through the ducts in the dwelling.

Baseboard:  A type of electrical heating system.  An electrical resistance system produces heat in the immediate area to be heated.

Hot Water:  Water is heated in a cast iron or steel boiler, the hot water rises and is pumped through pumps and radiators where heat is transferred by convection and radiation.

Gravity:  Air is heated in furnace, distributed through registers.   Air circulation is maintained with a fan but relies on scientific principals of heat rising and cold air sinking.

Space Heater:  A portable device for heating an enclosed space that does not have external heating ducts or connection to a chimney.

Heat Pump:  A device that gathers heat from outside and pumps it into the dwelling.  Not typically used in areas that sustain extreme cold.

Steam:  Water vapor kept under pressure so as to supply energy for heating.

In-Floor Heating:  Radiant floor systems pump heated water from a boiler through tubing laid in a pattern underneath the floor.  Electric radiant floors typically consist of electric cables built into the floor.

Radiant:  Supplies heat directly to the floor or to panels in the wall of ceiling of a house.

Geothermal:  Transferring heat to or from the ground with the use of a geothermal heat pump.

Ductless Mini-Split:  A ductless heating system with an outdoor compressor and an indoor air handling unit.

Boiler:  A water boiler used to create radiant heat.

Dual Fuel/Off Peak:  A heating system that pairs an electric heating pump with a furnace (usually gas or oil) that can alternate fuel sources based on peak electrical demand.

Fireplace:  A place for domestic fire with a chimney.

Wood Stove:  A stove heating source fueled by wood.

Outdoor Furnace:  An outdoor stove furnace that transfers heat indoors.

Other:  Anything that does not fit into any of the preceding categories.