While you won't find LEDs in too many household lighting fixtures these days, there are a couple of good reasons to want them there in greater numbers.
First, there's the reduced energy use. The LED method of producing light loses far less energy to heat than do other lighting technologies. It's dramatically more efficient than the vacuum/filament method used in incandescent bulbs -- sometimes around 85 percent more efficient; and it's even about 5 percent more efficient than the CFL's plasma-tube approach [source: Taub].
A single light fixture stocked with a 60-watt incandescent bulb consumes about 525 kWh of electricity in a year; put a GeoBulb LED bulb in that light fixture, and the annual energy use is more like 65 kWh [source: Sundance]. The annual CO2 reduction is in the hundreds of pounds for a single lamp.
But energy-efficiency is just part of the story. The other part is time-efficiency: You could go 20 years without having to change an LED light bulb. Solid-state lights like LEDs are more stable light sources than incandescent or fluorescent bulbs, and the difference is startling: A typical incandescent bulb lasts about 750 hours; a Geobulb lasts 30,000 hours [source: Sundance].
Some LED bulbs last up to 50,000 hours [source: Linden].
Because of that time benefit, things get a bit more muddled when you get into the cost issue. A 60-watt LED replacement bulb runs in the area of $100, and even the lower-output versions, used for things like spot lighting, will cost between $40 and $80. That's compared to a $1 incandescent and a $2 fluorescent bulb.
The reality is, even at $100 for a single bulb, LEDs will end up saving money in the long run, because you only need one every decade or two and you spend less money on home lighting, which can account for about 7 percent of your electric bill [source: Greener Choices]. But the upfront cost is still pretty prohibitive. Lots of people simply can't spend a thousand dollars for 10 light bulbs.
The other primary LED issue -- degradation in the color of the light to something bluish -- has been solved in newer models. LEDs can produce the same soft, white light as a regular bulb. (Although Energy Star does recommend looking for the Energy Star label when shopping for LED bulbs, since the organization tests for color stability as part of its certification criteria.)
So price is really the only problem with LED light bulbs right now. But that could change pretty soon.