The New York Times
posts about an Economist
article that predicts that more efficient light bulbs could increase the amount of electricity demanded.
...history suggests that better technology 'will serve merely to increase the demand for light.'
The logic is that people demand what the bulbs produce--light. More efficient bulbs reduce the price of that good, causing demand to rise. In this case, demand appears to be very responsive (elastic), leading not only to more light consumption but more energy consumption.