Sony Bravia WE5 energy-saving TV uses facial recognition to switch itself off if you fall asleep. Photograph: PR.

The next time you fall asleep in front of the TV, someone, or rather something, could be watching you – and all in the name of saving energy.

Sony last year launched a new addition to its Bravia range of TVs, which features facial recognition technology similar to that found in the electronics giants' most advanced cameras. As a result, the
TV is able to "watch" you and can turn the picture off if you nod off
in front of Match of the Day, saving the energy used by the backlight.

The Bravia WE5 also features a heat and motion sensor that similarly allows the system to turn off the picture if it is left playing to an empty
room, and an ambient light sensor that reduces the output from the TV's
backlight depending on the brightness of the room.

A spokeswoman for the company said that the new sensor technology will now be rolled out to other models in the Bravia 2010 range, delivering significant
energy savings to those viewers guilty of leaving their TV on when it is
not being watched.

"If you wonder off to make as cup of tea you will still be able to hear the TV but it won't be wasting energy showing the picture," she said, adding that the picture returns as soon as
someone walks into the room.

According to Sony, the new micro-tubular HCFL backlight also cuts the amount of power consumed by the TV by 50 per cent compared to previous LCD TVs.

The new innovations are part of a company-wide initiative designed to cut annual energy consumption of Sony products 30 per cent against a 2008/09 base
line by 2015.

The company spokeswoman said that its most recent TV had already met the target and that many product lines would aim to exceed the target. "The 30 per cent target is an average so a lot of
products like TVs will look to go far further than by 2015," she said.

The plan to roll out the sensor technology across new products follows Sony's recent high
profile commitment to deliver a "zero environmental footprint" by
2050, eliminating eliminating carbon emissions and the use of
non-renewable materials in its products and manufacturing.