I was reading the September 2006 issue of Fast Company last weekend, in which there is a really fascinating article on the effect of the Compact Fluorescent Lightbulb (CFL) and Walmart's hope to sell one of these lightbulbs to each person in the US (you can read it online: How Many Lightbulbs Does it Take to Change the World? One. And You're Looking At It.).

CFLs provide the same amount of brightness as a standard incandescent bulb, just use less energy - for example a CFL of 15W is equivalent to an incandescent of 60W in terms of brightness, it just uses a quarter of the energy.