We use a heat pump. Can I assume that you are in a warmer state and not a cold state? A heat pump works by drawing the outside air in and it separates out the warm air and pumps it into your house. If it gets too cold outside (which for us in FL, it is rare) then it doesn't work as well as you would like it to, because there is no warmth in the outside air to pump in. Like the previous poster said, our is part of our central a/c. It works great except for when it is super cold, like 30's or below. Overall we like it because it suits our needs for our climate here. If you live somewhere where it gets really cold though, don't do it.
at 11:12 AM on Nov. 1, 2010