Compact Fluorescent Lamps or CFL (often called energy saving bulbs) use around 1/5th of the power of an incandescent lamp meaning less power consumption and less heat output. CFL’s can screw into any normal light socket and they can be placed just an inch away from plants. This is a massive advantage over those still using HID lamps, as there is no wasted light, they really are a home growers dream. While the initial purchase cost of a CFL bulb is more than a traditional bulb the life span of them is ten times greater, add this to the amount you save on your energy bills and the long term cost is not more expensive.
One word of caution though, be very cautious when purchasing unbranded CFL lamps at online auction sites. There are dozens of cheap fake copies going around at the moment so when making a purchase try to do so from a reputable online seller. Stick to better known brands like the 125w 6400K CFL White/Blue Spectrum Lamp by Enviro-Gro-Lites which are ideal for indoor growers and propogation.