Over a 5 year period, nearly $70-$100 can be spent on wasted electricity from one power supply. Many in today's digital lifestyle have multiple computers, or computerized appliances, so even a 5% improvement over all of your equipment can mean hundreds (if not thousands) of dollars over time. I'm not an Al Gore-wannabe; I'm just pointing out that a slow leak of money adds up after a while. And it doesn't make sense to buy an exhorbitantly expensive power supply to combat the problem, because that's money out of your pocket, too.
Antec has introduced their EarthWatts line of power supplies to address this issue. These power supplies are available in three highly efficient models—380 Watt, 430 Watt, and 500 Watt—and are all 80 PLUS certified (the newest standard in power supply efficiency).