Economy 7 or 10 tariffs encourage consumers to use off peak energy. This is one of the major drivers behind the introduction of smart metering - and smart meters will be able to support this very easily. The smart meter display will clearly show when it is peak or off peak, so you'll know when to take advantage of off peak prices. Cheaper Economy 7 electricity tariffs can be used to lower the cost of electricity to power the heat pump.
Background information: Ground source heat pumps take low temperature 'ground heat' from underneath the ground and heat it up to a higher, more useful temperature to heat the rooms and the water supply in your home. It has the potential to cut your annual emissions by up to 50% and, depending on the fuel you're currently using, cut your heating bills even further.
You can find more information on ground source heat pumps at www.energysavingtrust.org.uk/Generate-your-own-energy/Ground-source-heat-pumps
