Wal-Mart has completed the first stage of a pilot project to use solar power at its retail stores.

Solar cell manufacturer SunPower has successfully installed a 390kW system at the Sam's Club store in Chino, the first of seven Wal-Mart facilities across California to take part in the project.

A further 15 Wal-Mart stores, Sam's Clubs and distribution centres in Hawaii will be included in the pilot to provide a total of around 4.6MW of power for the retail chain.

"Wal-Mart is moving forward with its commitment to conserve energy, reduce energy costs and lower greenhouse gas emissions, and this project is a step in the right direction," said Kim Saylors-Laster, vice president of energy at Wal-Mart.

Each solar power generating system may vary, but can provide up to 30 per cent of the power for the store at which it is installed.

"Installing the solar power systems will help reduce greenhouse gas emissions by 8,000 to 10,000 metric tonnes a year," said David Ozment, director of energy at Wal-Mart.

Wal-Mart described the project as a major step towards its goal of using 100 per cent renewable energy.

"Leading companies like Wal-Mart are turning to solar power because it makes good business sense and supports their environmental initiatives," said Tom Werner, chief executive at SunPower.

The project is being funded through a purchase agreement between Wal-Mart and SunPower in which there are no upfront costs for the installation. SunPower will charge for the power generated by the panels at a competitive rate.