From June customers in Hampshire, parts of West Sussex and Medway in Kent will have new meters installed.

They will pay 6% more than the standard rate for their water in June to September, and 2% less than the standard rate the rest of the year.

Southern Water says most people will end up paying about the same amount over the whole year.

Environmental benefit

The company says it will install 487,000 meters in the next five years, meaning 93% of its customers will have a meter by 2015.

It says metering is a fairer system as customers will only pay for what they use and are in control of their water use and bills.

There have been some small-scale trials before, and some water companies, including Severn Trent, Veolia Water East and South East Water, have seasonal tariffs for business customers.

But Southern Water, which supplies water to Sussex, Kent, Hampshire and the Isle of Wight, is the first company to roll out a scheme to nearly half a million people.

Seasonal tariffs are supported by the Environment Agency, which says water use by individuals in the South East needs to fall from 156 litres of water per day to 130 litres by 2030.

It says that is because forecasts suggest flows in some rivers could fall by 35% by 2050, as abstraction increases due to population growth and climate change impacts.

But research carried out by the Consumer Council for Water in 2007 found only 27% of people liked the idea.