We receive inquiries for heat pump on a regular basis and I think it is a good idea to cover the topic. Heat pump is essentially an air conditioner that is capable of running in a reverse cycle. There are a few types of heat pump: Air source, ground source, and water source. Due to the need and high cost for trenching or access to large bodies of water for the latter types, air source heat pump is the only common type used in urban residential area such as the Bay Area. Instead of rejecting the heat outside like an AC does in the summer, it rejects the heat inside in the winter. It is an alternative to the conventional gas or LP heating furnace.
The benefit of a heat pump system is that it uses electricity for its heat generation which reduces it carbon footprint when compared with a gas furnace. It also allows heating for areas that do not have ready gas supplies. However, the downside is that heat pump tends to lose its effectiveness when outdoor temperature drops below 45F. And from a operating cost it is more expensive to operate a heat pump in the Bay Area climate unless you have access to low cost electricity. And recently that option comes from solar panels that some homeowners have started to install on their roof.
Next time we will cover hybrid system and supplemental heat.