Geothermal Heat Pump
Maintaining a comfortable indoor temperature can use up to half of your home's energy [source: Energy Star]. That means green technologies that can help reduce your heating and cooling bills will have some of the quicker returns on investment.
If you have central heating and air in your home, the way it maintains the temperature is by exchanging air inside of your house and with the air outside. In the summer, that means your HVAC unit pumps out hot air as it cools the air inside, and in the winter it takes heat from outside and transfers it into your home. This is not the most efficient system, since in summer the outside air is hotter than you want and in winter it's usually much colder. A geothermal heat pump works the same way, but its heat exchange apparatus is buried underground, where temperatures are a lot more stable. This type of system can might cost you more in the beginning for installation, but it can reduce your heating and cooling costs by as much as 30 to 40 percent [source: Consumer Energy Center]!
Not only is a geothermal heat pump more efficient, but it's quieter than a conventional HVAC system, and it lasts a lot longer. Since none of the system is exposed to the elements, there's less chance of damage from weather or from vandalism and they are virtually maintenance-free [source: Energy Savers].