Energy giant Npower and tech firm RLtec are giving away thousands of "smart fridges" to test a new green technology.

The two companies are trialling dynamic demand, a process of cutting national electricity demand in real-time - known as "load-shedding" in the industry - to reduce the carbon emissions from fossil fuel-powered power stations and reservoirs on standby.

The smart fridges will be able to reduce their energy demand on a second-by-second basis in response to peaks.

A total of 3,000 smart fridges will be tested in consumers' homes, starting with a first phase involving the adaptation of 300 conventional fridges.

"The beauty of it is that you don't know it's happening and there's no safety risk with your fridge defrosting", RLtec's Paul Lazarevic told The Guardian.

"The trial will help us gain a better understanding of how dynamic demand can work to reduce our use of fossil fuels", said Lord Hunt, the Minister for Energy Innovation.

"If successful it could help pave the way for the uptake of this technology nation-wide, which could result in significant carbon savings of around 2million tonnes Co2 a year or higher".