The practical LED bulb is here!

Toshiba apparently will unveil an LED bulb with the light output of a 100 watt bulb that uses about 9 watts of electricity.

The only stumbling block is the price: about $100 dollars.

That should start dropping fast.

http://www.geeky-gadgets.com/toshiba-led-lightbulb-2-10-2009/

We will have to learn a measurement of brightness: the lumen (abbreviated lm)

These new bulbs do sound like you can get reasonable brightness for under 9 watts... perhaps even more efficient than compact fluorescents, which although they start off bright, lose about 20% light output after a year or so of heavy use. The LED bulbs seem to degrade much more slowly.

In practice, then, you would have to buy 4 compact fluorescents to equal the service life of one LED bulb. The 100 W compact fluorescent output would be good for a year, then be 80% for the last 4 years of its service life, let's say light output would be like an 80 W incandescent bulb but using 20 W. The new warm white bulbs seem to output about the light of an 80 W incandescent bulb, but uses about 10 watts, approximately halving the electricity use for a comparable amount of warm white light over a compact fluorescent. Good quality compact fluorescents are still about $10 dollars in Japan, 4 of them would cost $40, and therefore the premium would be about $60 if these bulbs go for about $100. Run at 10 hours per day, the compact fluorescent would consume 10 X 20W/day = 200 W/day = 4 cents per day versus 2 cents per day for the LED, over a year saving about $7, for a payback period of about 9 years. If they can just get the price down to about $40, then the payback would start immediately.