NEW European-wide rules designed to make household appliances more energy efficient will mean coffee machines switch off automatically once a drink has been brewed.

The rules, which came into effect yesterday, affect a wide range of domestic devices including internet routers, smart televisions and printers.

Online retailers will have to display energy efficiency labels alongside goods to inform shoppers, in the same way as is already done with electrical goods in bricks and mortar outlets, and gas ovens will also have to display energy ratings.

The measures are part of the European Union (EU) extended Energy Labelling Directive and the Ecodesign Directive, which includes new rules on standby modes for networked appliances, commonly known as the "internet of things".

All new items sold should be able to switch automatically into a low power standby mode if no main task is performed, in a move which experts say will save the average household £32 a year.

Drip filter coffee machines are affected, and those without insulated jugs must switch to a low power standby mode 40 minutes after the end of the last brewing cycle. Those with jugs which keep the coffee warm and preserve its taste without further heating - must switch off after five minutes.

The Commission claims consumers will not notice a difference, as coffee in drip-filter machines without an insulated jug is undrinkable after 40 minutes anyway, and it claims the rule will reduce the consumption of each device by 30 per cent or £36 over the lifetime of a drip filter model.

The measures affecting modems, routers, printers, internet connected televisions and other electronic devices are also designed to ensure they use only a trickle of energy when not in use. Currently, many gadgets are connected to the internet 24/7, using 25-100 watts while their owners sleep.

Energy efficiency labels are designed to make it easier for consumers to make comparisons wherever they shop. The Commission said labels on gas ovens would also benefit consumers as the difference in efficiency between the most and least efficient gas ovens could make a £143 difference over the lifetime of the product.

Similar rule changes recently led to controversy after popular high-wattage vacuum cleaners were banned, angering some consumers and leading to a rush to purchase the devices. But energy experts have argued that some manufacturers artificially increased the wattage of cleaners to appeal to consumers, even though there was no great benefit in terms of performance. Inventor James Dyson has backed the regulations, and argues many vacuum cleaners could use less energy without a loss of cleaning power.

European Consumer Organisation director general Monique Goyens said: "Improving the energy consumption levels of everyday consumer products is the right approach to contribute some relief to consumers from increasing energy bills.

"With purchases increasingly moving online it makes perfect sense for shoppers to have a useful energy label at their disposal to compare products."

Marylyn Haines Evans, public affairs chairwoman of the National Federation of Women's Institutes, said: "Nobody likes to waste energy, and at a time when energy bills are increasing, having appliances designed to be sparing with electricity is definitely a good thing for your household finances.

"Coffee is one of the many products threatened by climate change, so it's also good to know that when you're making a cup, you're doing your bit to cut down on carbon emissions too.

"With a better designed appliance you can enjoy a coffee without the bitter taste of wasting energy or adding unnecessarily to the climate problem."

The Commission says its measures on stand-by devices will reduce energy consumption by almost 75 terawatt-hours (TWh) without undermining the quality of products on sale. As well as saving on energy bills, the rules are predicted to cut CO2 emissions by 28 million tons, equivalent to the annual emissions of 1.5 million households.