Energy efficiency deals not only with the quantity of energy a home uses but also how efficiently it uses the energy that it consumes.  Energy efficiency can be greatly improved through several different methods including site orientation, implementing a proper building envelope, quality mechanical systems, and the use of Energy Star rated appliances, fixtures, and light bulbs.  Site orientation, known as passive solar design, shades the house during the warmest hours of the days simply based on the direction the home faces.  Quality mechanical systems can include solar panels for electricity, a geothermal system for heating and cooling, and even tankless hot water systems that only heat the water as it is needed.  Energy Star rated appliances, fixtures, and light bulbs cost a little more in the initial purchase, but quickly pay for themselves in lower energy bills down the road.

The following is a diagram showing how Geothermal heating and cooling systems work.