A prize-winning light bulb that lasts for 20 years has gone on sale in the US on Sunday, which is 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 dollars (37 pounds).
Philips has arranged discounts with shops that will sell the bulb meaning some could buy it for only 20 dollars (12 pounds).
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 bulb 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.