Heat Pump systems are a suggested alternative to traditional Oil/Gas heating solutions because of their reported efficiency. Wiki describes Heat Pumps as a system that transfers heat energy from a source of another heat called a thermal reservoir.
As the diagram depicts, Heat pumps move thermal energy in the opposite direction of heat transfer, by absorbing heat from a cold space and releasing it to a warmer one. A heat pump uses external power to accomplish the work of transferring energy from the heat source to the heat sink. The most common design of a heat pump involves four main components – a condenser, an expansion valve, an evaporator and a compressor.