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The technology, called Combined Heat and Power (CHP), works by making use of the heat that is created when electricity is generated. In large power stations, this heat is dumped as a useless by-product but, by installing mini-power stations at its stores, Tesco will use the heat to warm its stores.

The technology can cut carbon emissions from a store by up to 10%. By building 50, Tesco will save the equivalent energy bill of five stores. Tesco has been testing CHP since 2006, and already has plants working at 10 sites.

Lucy Neville-Rolfe, Corporate & Legal Affairs Director, said:
"At Tesco, we care about the environment and want to lead the way in preparing for a low carbon future. We are now ready to unveil the scale of our plans to use Combined Heat and Power to cut our carbon footprint.

"We are applying for planning permission to build a CHP plant at all our larger stores and intend to build them as an integrated part of every new Extra or Superstore.

"Our trials have shown us that this is a much more efficient way to create electricity so it makes sense – both financially and environmentally – for us to put our full weight behind it. We expect our investments in CHP to have paid back within 8 years and, as the technology is refined and the market matures, this will come down further still."

Most of Tesco's CHP plants will run on gas but, last month, it opened a plant at its Colney Hatch store which runs on bio-fuels such as UK-grown vegetable oil. As vegetable oil is a renewable material rather than a fossil fuel, the CO2 emitted is equal to the amount it has absorbed whilst growing, effectively making the energy used in the store carbon neutral.

As well as supporting the store's heating needs, the Colney Hatch plant is used to produce cooling too. By passing the heat through a hot water driven 'adsorption' system, chilled water is produced which is used to support the energy needs of its refrigeration and air conditioning systems. This is the first commercial application for an adsorption chiller in the UK.

Dr Doug Parr, Policy Director for Greenpeace commented:
"As part of their responsibility to tackle climate change, it's vital that big companies choose to put money into the most efficient technologies available. Combined heat and power stations are a clear winner in this respect, as they cut down on waste and use fuel in the smartest way possible. In tough economic times this kind of canny investment is more important than ever, as this move will slash costs as well as emissions."