A further 44% of the 1,500GWh order will come from good quality combined heat and power (CHP) - a gas-fired product that is cleaner than many alternative fossil fuels.
The contract is part of the supermarket chain’s energy-efficient initiative. It has allocated £14m to reducing its energy consumption by 11% during the next two years to meet government targets of 15.4% by 2015.
The renewable and CHP energy qualify for Climate Change Levy exemption - a tax for business users designed to help reduce greenhouse gas emissions and encourage the purchase of renewable energy.
Energy manager Julius Brinkworth said: “We want to do as much as we can to reduce our energy consumption.”