Consumers who like a powerful vacuum cleaner have been urged to buy one now before new energy rules that restrict motor sizes come into effect next month.
A new EU energy label to be introduced from September 1 means manufacturers will not be able to make or import vacuum cleaners with a motor that exceeds 1,600 watts.
The Which? consumer group said many of its Best Buy models have motor sizes that exceed this, "so if you're in the market for a powerful vacuum, you should act quickly, before all of the models currently available sell out".
Of seven awarded Best Buy status since January 2013, five have motors of more than 1,600 watts, it said.
The maximum wattage will be lowered even further to 900 watts by 2017. Current cleaners boast an average of 1,800 watts.
The watchdog said a Best Buy 2,200-watt vacuum cleaner cost around £27 a year to run in electricity - only around £8 more than the best-scoring 1,600-watt model it had tested.
For the first time, the labels will give vacuum cleaners A to G ratings for energy use, cleaning performance on carpets and hard floors, and dust emissions.
But the scheme is self-regulating, meaning that manufacturers will create their own labels, and Which? said it was unclear if the results were being corroborated by an independent third party.
It also pointed out that vacuums would be tested when brand new, unlike Which's own testing that took into account loss of suction as the container fills.
Which? said: "We have already seen some interesting A to G ratings for cleaning.
"Manufacturers that traditionally don't do well in our tests have had A ratings across the board, while those that consistently do well haven't scored as highly.
"Have some previously lower-scoring manufacturers suddenly come across a winning suction formula? We can't wait to get the latest batch of vacuum cleaners to our lab to find out."
Sir James Dyson, whose company pioneered 'bagless' vacuums, said he believed the label itself was a good idea, pointing out that he had never made a machine over 1,600 watts.
But he said there were many engineering aspects other than the size of the machine to take into account, and he feared strong performing vacuum cleaners would be rated badly and lead the consumer to buy a machine which simply did not work efficiently.
He said: "Efficient technology isn't the result of an energy label, it's the result of costly research and development.
"Since I ripped the bag from my Hoover Junior and did away with the need for environmentally costly consumables, the approach has always been the same - develop high performing technology that uses
less material, less energy and has no hidden costs."
The European Commission believes the new regulations will mean better vacuum cleaners for consumers.
European Commission spokeswoman for energy Marlene Holzner said in a blog: "As a result of the new EU eco-design and labelling regulations, consumers will also get better vacuum cleaners.
"In the past there was no legislation on vacuum cleaners and companies could sell poorly performing vacuum cleaners."
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