A prize-winning, super-energy-saving LED bulb from Dutch electronics giant Philips said to last over 20 years went on sale Sunday to coincide with Earth Day.

The bulb that won the US Department of Energy's "Bright Tomorrow Lighting Prize" was available from retailers for $50, down from an initial $60 price tag. The company said it was planning discounts to bring the cost down to as little as $25.

The 10-watt LED bulb (light-emitting diode) was deemed an efficient alternative to the standard 60-watt incandescent bulb, and rated to last 30,000 hours -- when used four hours a day, that translates to a more than two-decade life span, according to the company.

For consumers attentive to cost, Philips said the price tag was easily offset by energy savings of $165 over its lifetime.

The new bulb, which gives off 940 lumens, a soft white light, is "83 percent more energy efficient than the standard 60-watt incandescent," said Philips' North America executive Ed Crawford in announcing upcoming rebates.

Incandescent bulbs are power-sucking classics being phased out in countries around the world, replaced by energy-efficient CFL versions containing toxic mercury that make them hazardous to toss in the rubbish.

Philips' omni-directional bulb, which contains no mercury, began life as the sole entrant to the US government competition seeking ways to replace the common light bulb, and was submitted in 2009 after 18 months of testing.

LED bulbs face competition from compact fluorescent lights that approach seek similar efficiency levels, and cost far less.

The symbolic choice of Sunday's Earth Day release however saw Philips branding their bulb as the environmentally friendly choice.

Now in its 42 year, International Earth Day aims to bring attention to climate change and pollution, and highlight ways to save energy.

According to Philips, if every 60-watt incandescent bulb in the United States was replaced with their prize winner, "the nation would save about 35 terawatt-hours of electricity or $3.9 billion in one year."

A nationwide changeover would also avoid 20 million metric tons of carbon emissions, said the company -- equivalent to removing some 4 million cars from the roads.

"Consumers are no longer looking at a product that will last just six months to a year, they are looking at a product that is much more efficient and will be with them for decades," Crawford said ahead of the release.

"With LED bulbs, we are looking at a wholesale change in buying lighting technology, going from a disposable good to a durable good," he added.

Philips said it has partnered with over 280 US utility companies for the rebates and 230 more utility firms are expected to join the program in June.