A gas electric system is probably the most popular system in our area. They use natural gas or in some of the rural areas, LP gas. And that gas is used to fuel the flame that heats up the furnace. Then the blower inside the furnace sends that heat on into the ductwork and into your house. Of course, the air conditioner runs on electricity and so that's why these are called gas electric systems. A heat pump system is used in areas where gas isn't available. Also with the way things are looking, all electric heat pump systems will soon be the way a lot of states mandate fuel usage when it comes to heating and air. Anyways, heat pumps use the indoor unit and the outdoor unit together, whether in air conditioning mode or heating mode. It's all electric, which means no emissions. And I will tell you that these conventional style heat pumps aren't the most efficient systems in the world when it comes to heating your house. And I'm not talking about the Mitsubishi variable speed systems either. I say that because outdoor units are expensive to run, right? The most expensive thing to run in your house actually. You've seen your electric bill in the summertime, right? And you're running that outdoor compressor in heating and cooling modes. The colder it gets outside, the less capacity the outdoor heat pump has. So it uses supplemental heat strips to keep the warm air flowing inside. And those heat strips are just about as expensive to run as the outdoor unit, doubling the cost of using your air conditioner on the coldest days of the year.