Nearly one in five fridges, dishwashers, microwaves and other household gadgets guzzle more energy than advertised according to a three-year survey of Europe’s home appliance industry.

One AEG fridge freezer tested used 12% more power than claimed, while a Hotpoint tumble-drier was found to be sucking considerable power while supposedly in ‘off’ mode.

The Marketwatch study also found digital radios using over twice their stated energy when turned off, dishwashers not washing properly in eco cycle mode, and vacuum cleaners hoovering up 54% more electricity from the plug than advertised.

In all, 18 of the 100 products were non-compliant with EU ecodesign laws, according to the tests by several European efficiency groups, led by the Energy Saving Trust (EST) in the UK.

Dr Fanoula Ziouzia, the EST’s head of products, said: “While this was a targeted sample, we suspect that as many as one in 10 household appliances sold today consume more energy than the manufacturer states. This could be misleading for consumers and result in higher energy bills – and true product cost – than they would anticipate.”

Efficiency studies estimate that misleading energy claims by product manufacturers could cost consumers around €10.5bn (£8bn) in extra bills.

But the added annual costs in the latest Marketwatch survey are not punitive individually, ranging from an extra £18 for an Azatom sound bar, to £20 for a Kunft vacuum cleaner, or £31 for an AEG fridge freeze.

Stewart Muir, a certification manager at the EST said: “We only covered a small proportion of products. The cumulative extra energy used across the entire product market ranges could add up to a substantial cost to consumers.”

Ecodesign laws are primarily meant to cut carbon emissions by preventing wasteful energy use. The efficiency group Clasp expects a 10% shortfall in energy saving targets for products to translate into an extra 47m tonnes of CO2 equivalent reaching the atmosphere by 2020.

A problem among some EU market surveillance authorities is widely recognised by campaigners and manufacturers alike - although the UK National Measurements and Regulations Office is generally well-respected.

But a spokeswoman for the Association of Manufacturers of Domestic Appliances (Amdea) said that talk of its members failing to meet EU ecodesign targets was a “big if”.

She said: “Our members are very committed to this legislation and have spent a great deal of money on ensuring that their products are more energy efficient. They would argue that they have had a lot of success in doing that.”

Six of the 18 failing companies in the Marketwatch survey refused to enter into dialogue with the EST about the test results. Most companies though showed an honest engagement with the issues raised by the survey.

Several firms have since developed automatic software updates that can be downloaded by consumers. But technicians at the EST say the very ease with which energy consumption can be changed raises concerns for them that software updates could, theoretically, add to energy use as well.

“There is nothing stopping it,” Muir said. “If you can update products once they are in the home, they could potentially consume more afterwards than they did when they were originally tested. It is very difficult to police on a large scale.”