Scottish Water, which uses a large amount of electricity to provide its essential services, has cut energy costs by installing a range of renewable technologies such as solar panels, hydro and wind turbines to generate enough electricity to power as many of its sites as possible.
Water treatment works at Turret in Perthshire, Lintrathen in Angus and Castle Moffat in East Lothian, along with the waste water treatment works at Tannadice in Angus, are now considered self-sufficient.
This is because, due to the amount of electricity created on-site from hydro power, they generate more energy than they consume over the year.
Chris Toop, Scottish Water's general manager for energy, said: "To keep the cost of our services as low as possible it is essential that we develop our approach to energy management and continue to reduce our carbon footprint.
"We currently generate 28 gigawatt hours (GWh) of the 450GWh of energy we need every year to keep high-quality water flowing through taps to our customers, and safely return waste water to the environment. We are on track to double the amount of energy we generate ourselves within two years.
"We are doing this through a mix of renewable technologies such as solar, hydro and wind power. Some of our sites in Perthshire, Angus and East Lothian already generate at least the equivalent amount of energy they need to operate."
The Scottish Government has set a target for the equivalent of 100% of the nation's electricity consumption to come from renewables by 2020.
Mr Toop said: "Where appropriate, we're exploring opportunities to export energy to the National Grid, showing it is possible to maximise the economic advantages of Scotland's water resources in the spirit of a Hydro Nation and contribute to national renewable energy targets."
Meanwhile, Scottish Water has completed the construction of a new £1.7 million waste water treatment works at Caddonfoot in the Scottish Borders.
The investment is part of a £12.5m programme which Scottish Water is carrying out to improve and protect the natural environment of the River Tweed, a world renowned salmon river which is the lifeblood of the Borders.
Project Manager Jim Tudhope said: "Throughout the Borders, Scottish Water is investing to enhance and protect the natural environment. The completion of the waste water treatment works at Caddonfoot is part of our multi-million-pound investment programme to replace and renew our equipment. It also demonstrates our commitment to deliver the best possible service to our customers."
The new facility, which also serves nearby Clovenfords, replaces an outdated septic tank.
Bill Elliot, Scottish Water's community team manager for the Borders added: "Through this investment we're protecting the Borders' natural environment, which is vital to the region's economy and attracts large numbers of visitors and anglers each year."
Scottish Borders councillor Gavin Logan said: "Scottish Water is to be congratulated for making this huge investment. Coupled with the extensive upgrade of the sewage pipework this represents a massive commitment.
"The old septic tank system was out of date, so these improvements will make a significant improvement to the water quality which is so important to the salmon fishing on the River Tweed. It will also add much needed protection to the natural environment."