Compact Florescent Lamps.
Did you know that if you change a 100W regular light bulb for a 25W CFL (which gives a similar light output), you not only save 75% of the energy cost but also save the equivalent amount of carbon going into the atmosphere that your car pumps out in 93 miles?
A regular light bulb only puts out 8% of the electrical energy it uses as light anyway. The rest is heat. Now you know why they’re so darned hot!