There are two types of air source systems you need to know about. The first is the air-to-water system, which gives off heat via your wet central heating system. These are suited to giving out heat at relatively low temperatures over a long period of time, so they are ideal for underfloor heating systems or large radiators.
The second type is the air-to-air system. This system heats your home by producing warm air which is circulated by fans. A drawback of the air-to-air system is not very well suited to heating your water.
If the idea of plucking energy out of thin air appeals to you, you might want to look into getting an Air Source Heat Pump for your own home. They may not be considered quite as efficient as other green heating systems such as photovoltaic panels, but heat pumps will still have a major impact on cutting your energy costs and lowering your carbon footprint.