The smart meters will show detailed information of a customer's energy costs in real time, the gas and electricity company said. They will also be portable around the house.

The devices will provide the option for customers to compare their energy use by the hour, day, week or year, as well as to set energy targets - with a traffic light system warning households when they are using large amounts of electricity.

The display was developed by smart metering technology firm Landis+Gyr, and will also show homes that have solar panels full details of the energy they are generating.

The arrival of smart meters means a shift in the way people are charged - with the end of estimated bills. The rollout will take up to eight years between the different energy firms.

British Gas has already fitted 400,000 businesses across the UK with smart meters.Dean Keeling, managing director of home smart metering at British Gas, said: "We want people to understand the energy they use and make informed choices about when to use it and how to save it."