How we watch now: tune in, log on, call up

But when they do watch "traditional" television, the taste of 16- to 24-year-olds is remarkably similar to that of those over 65. Both like entertainment and contemporary music shows while 16- to 24-year- olds watch slightly more soap operas and factual programmes than people over 65. The big difference between the age groups, according to the report, is in the area of news and weather programming.

Among those over 65, TV news and weather programmes account for 14% of all viewing, compared to just 7% of all viewing by 16- to 24-year-olds.

The Ofcom report shows that online advertising hit £2.8bn last year, up 40%, and eclipsing spending on the traditional terrestrial channels ITV1, Channel 4, S4C and Five for the first time. Given how much more time people spend watching TV than using the internet the figures look incongruous, but the Ofcom report does not take into account the amount of time British consumers spend online at work.

In fact, take-up of residential internet services is slowing as the digital divide between rich and poor becomes ever more obvious. Most households that have a computer are already online with PC penetration running at 72% in the UK and internet penetration close behind at 67%. Broadband take-up - at 58% of UK households - has slowed not least because younger consumers such as students are opting to buy mobile phone "dongles" that give internet access and are often cheaper than a lengthy broadband contract. Over 2 million Britons now use mobile internet services, with sales of dongles nearly doubling between February and June this year to over 130,000 a month.

Why we should turn off our electrical appliances

British households are wasting the annual output of a large power station by failing to switch off their flatscreen televisions, set-top boxes, and internet networks when they are not being used, according to Ofcom's latest Communications Market report.

The equivalent output of the 1,500MW Didcot B power station in Oxfordshire could be saved each year if every home with a set-top box switched it off at night; that would conserve enough electricity to make 80bn cups of tea.

Consumer electronics account for about a third of home energy use, according to the Energy Saving Trust, but that use is forecast to balloon to 45% by 2020 as more people buy more gadgets.

The rise in average residential energy bills to just over £1,000 a year has made people more energy aware, but only when it comes to buying obviously power-hungry devices such as fridges and freezers, according to Ofcom.

Almost three quarters of Britons, when quizzed by the regulator, classed themselves as caring about the environment, and more than half said they had compared the green credentials of white goods before making a purchase. But only 39% of people think about the environmental impact of a new TV, DVD player or computer.

When they get it home, meanwhile, most people leave their new kit switched on all the time, unnecessarily wasting electricity.

Three quarters of people rarely switch off their set-top box, according to Ofcom, and that figure jumps to 83% for owners of a wireless home network. Plasma screens are particularly power hungry, according to the regulator, with the average set using three times the power of a normal TV when in use, and twice the power when left on standby.

The average satellite set-top box gobbles up four and a half times the power of a flatscreen LCD television in the same state. Even a Freeview box uses twice the power of a flatscreen TV when left on standby.

Almost half the country's mobile phone users, meanwhile, waste electricity by charging their handsets overnight, when in fact most models only need to be plugged in for about two hours. People aged between 16 to 24 are particularly guilty of this, with 80% doing it at least some of the time.

· This article was amended on Saturday August 23 2008. We were wrong to say that Ofcom's annual communications market report showed that 14% of pensioners watched television news and weather programmes, compared with just 7% of 16- to 24-year-olds. The report showed that TV news and weather accounted for 14% of all viewing by people over 65, and 7% of all viewing by 16- to 24-year-olds. This has been corrected.