There are different types of heat pumps on the market.
There are geothermal, water-source, air-source and ductless heat pumps which all combine both heating and cooling capacity into a single unit.
The most common is an air-source heat pump. Like the name implies, this style of system makes use of ambient heat found in the outdoor air. Even when the weather is cold, there is heat energy available. The heat pump draws the heat out of the air, compresses it to a high temperature and delivers it into the home by way of refrigerant. Because the heating process makes use of existing heat rather than generating it, there is no combustion. Fossil fuels aren’t burned to produce heat. There are no worries over carbon monoxide, carbon dioxide, formaldehyde, fumes or greenhouse gasses. This type of system is especially safe and environmentally friendly. During the summer months, the heat pump acts very much like a conventional air conditioner. It literally reverses the flow of refrigerant to pull heat out of the home and transfer it outdoors, creating a cooling effect. Heat pumps are especially good at handling excess humidity. Modern and better quality models include adaptable-speed technology that automatically adjusts output to the requirements of the indoor space. This provides outstanding energy efficiency and very even comfort levels. Although heat pumps are more expensive to purchase and install than more traditional systems, they do pay for themselves in savings on utility bills. Plus, there is only one unit to buy and maintain. Heat pumps take up less space, are especially quiet and offer year round comfort.