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A prize-winning light bulb that lasts for 20 years is going on sale in the US on Sunday - also known as Earth Day.

Made by Dutch electronics giant Philips, the bulb swaps filaments for light-emitting diodes to provide illumination.

Using LEDs endows the light with a long life and a hefty price tag. The first versions are set to cost $60 (£37).

Philips has arranged discounts with shops that will sell the bulb meaning some could buy it for only $20 (£12).

The bulb triumphed in the Bright Tomorrow competition run by the US Department of Energy that aimed to find an energy efficient alternative to the 60-watt incandescent light bulb.

The DoE challenged firms to develop a design that gave out a warm light similar to that from an incandescent bulbs but was much more energy efficient.

Philips was the only entrant for the competition and its design underwent 18 months of testing before being declared a winner.

A cheaper and less efficient version of the LED bulb is already sold by Philips in the US and Europe.

LED bulbs face competition from compact fluorescent lights which are almost as energy efficient and cost a lot less.

Sales of more energy efficient bulbs are being aided by official moves to end production of higher wattage incandescent bulbs.

Production of 100 watt bulbs has ceased in the US and Europe. Production of 60 watt bulbs has been stopped in Europe and is being phased out in the US. From 2014, incandescent bulbs of 40 watts or above will be banned in the US.