Unless there is a sign on the property, you typically cannot see when a home is heated and cooled with an earth energy system, geothermal heat pump, or geoexchange system (common names for the same thing). Earth energy systems use the ground to create heating and cooling, so as you would expect, most of the system is buried underground, invisible, conveniently out of the way, and silent. Earth energy is one of the most efficient renewable energy systems available, and is always available for use.
Dirt is something we're accustomed to standing on, but not something we typically think of as a battery. Earth energy systems store and extract heat energy from the ground in much the same way as your fridge extracts heat from its interior. The compressor circuit in your fridge takes heat out of the inside of the unit (making it cold) and moves that heat out into the room. The same process also works in reverse, where you can take heat from the room, and move it into the refrigerator. That's essentially what a heat pump does: move heat from one space to another. Geothermal or earth energy heat pumps take advantage of the fact that the earth's temperature below a certain depth (5-6ft) is a relatively constant ~10 degrees C all year, making it a very large, very predictable, extremely efficient battery of heat energy regardless of the outdoor air temperature. By installing looped pipes either horizontally (in trenches) and/or vertically (in bore holes), heat pumps can pump fluid through the ground just like your fridge compressor pumps fluid through the coils on the back of your fridge, and can then cool or heat your home with the energy stored in the earth. For a complete description of the technology, see the earth energy section of the CanREN website developed by Natural Resources Canada.