Heat pumps are magic. For every unit of electrical energy you put in to the system, you get between 3 and 4 units of heat out. Especially good for new build houses or if you have underfloor heating. 

You may not think it, but there is free heat energy all around your home – in the ground! Ground source heat pumps tap in to all this low level heat and draw it into your home.

Essentially they are long looped pipes buried in the ground full of water (well, liquid refrigerant actually). The liquid in the pipes is warmed by the ground, and then pumped into the house and used to heat living spaces. In hot summer months, the system works in reverse and acts to remove excess heat from the house to the ground.

How do they work?

They work because the ground’s temperature is pretty constant throughout the year (about 11 or 12^oC), whatever the air temperature is doing. Therefore in cold winter months, the ground remains warmer, and in hot summer months, the ground is cooler than air temperature.

They are made up of three main parts:

• A piping system that absorbs heat from the ground around your house
• A heat pump & exchanger, which is similar to, although unfortunately more expensive than the one in your fridge
• Heating system (but you'’ve probably got one of those already. You can use your radiators, but you get the best results with underfloor heating)

The system does mean you have to run an electric pump, however for every 1 unit of electric energy put into the pump, you get out between 3 and 4 units of heat energy! Sounds great doesn't it? But don't forget that heat energy (eg from gas supplies or wood burning) is usually cheaper than electric energy, so you shouldn't really compare these directly.

What types are available?

The ground loop system can be installed in three main ways, either vertically (deep into the ground), horizontally (under your roses), or if you are lucky enough to live next to a pond, lake or river, into and out of a water source.

Heat pumps can be installed on almost any size plot: under lawns, landscaped areas, driveways, or even under the house itself. An existing house can be retrofitted with a heat pump using the piping already there.

How much do they cost?

A typical 8 to 12kW system costs £6,000 to £12,000 plus the price of connection to the distribution system. This can vary with property and location.

For more information visit http://www.lowcarbonbuildings.org.uk/micro/ground/.