Anglian Water has installed five solar farms on its sites.
They will produce 1.8 million KWh of electricity per year – equivalent to powering 500 homes.
The firm expects the solar farms to provide between 10% and 50% of the energy needed in the water treatment centres which have high levels of energy use.
The solar farms are installed in Chelmsford, Daventry, Lincoln, Bedford and Basildon.
The company claims the projects are part of an ongoing drive to be more energy efficient and produce more energy from renewable sources.
Matt Pluke, Energy Manager at Anglian Water said: “This is very exciting news for us. This is yet another way we can reduce our energy costs and reduce our impact on the climate. Across some of our Water Recycling Centres we’ve already installed a fleet of combined heat and power engines which create energy from the gas released as a by-product of the water recycling process.
“The next step was to identify a number of energy-intensive sites where we can create clean energy from solar panels. By using this space, which would otherwise stand empty, we will be getting the best value out of the land we own whilst reducing our carbon footprint.”
Earlier this week Scottish Water installed 1,000 solar panels at a major water treatment works in Scotland.