Energy Efficiency is Better, Not Greener or Cheaper

From the Scientific American:

The researchers looked at light consumption since the year 1700. Even though today's compact fluorescents are 500 times more efficient than candles and whale oil lamps, what we spend on overall lighting hasn't gone down. It's just increased proportionately to our wealth. For the past 300 years we've consistently spent just about seven-tenths-of-one-percent of our gross domestic product on artificial lighting.

When one factor changes, others will too. That's not to say light improvements aren't good, they just aren't necessarily going to help us spend less on them.