For residential customers in the U.S., the average price of electricity has recently* been at $0.115 per kilowatt-hour. This works out to almost exactly $1.00 per Watt-year:Consider it passed.
Leave a 100 Watt light bulb on for a year, pay $100.
I found this surprising when I calculated it. The number is simple, memorable, and encourages conservation. Pass it on.
via Eric Drexler via TreeHugger