The new EU energy rule means manufacturers will not be able to make or import vacuum cleaners with a motor that exceeds 900 watts.
Vacuum cleaners are subject to EU energy labelling and ecodesign requirements, and the European Commission website says that by switching to one of the most energy efficient models, people can save 70 euro over the lifetime of the product.
The website says: "With more efficient vacuum cleaners, Europe as a whole can save up to 20 TWh of electricity per year by 2020. This is equivalent to the annual household electricity consumption of Belgium.
"It also means over 6 million tonnes of CO2 will not be emitted - about the annual emissions of eight medium-sized power plants."
It adds: "From September 2017, the most efficient vacuum cleaners will carry a label of A+++. These ratings take into account the vacuum cleaners' total power and how efficiently that power is used to pick up dust."
Vacuum cleaner salesman Howard Johnson, who works in Coventry, told BBC News: "People want a more powerful vacuum cleaner but they can't see that more power doesn't mean more suction.
"The lower power machines are perfectly adequate, and better for the planet."