The return of the incandescent light bulb
Traditionally incandescent light bulbs waste a lot of energy, only emitting about 5% as light. Fluorescent and LED technology is better, managing to reach up to 14% efficiency.
Now the attention is back on incandescent light bulbs, as researchers have found a way to recycle the heat given off and use it to produce more light instead. They believe it may be possible to achieve 40% efficiency like this!
Heard this on the radio earlier, but h/t to Nicholas Berry for the link.