Replacing Light bulbs with LED may not reduce energy consumption.

[auroraglacialis]

This was in todays science newsletter:

LEDs promise brighter future, not necessarily greener

A study looked at the reaction of civilization to prior efficiency increases in technology. The main focus is on light use, but the same can be applied to many other technologies like cars, freezers, air conditioning,...
The authors looked at light use and its efficiency in correlation with energy availability and energy consumption.

"Over the past three centuries, according to well-accepted studies from a range of sources, the world has spent about 0.72 percent of the world's per capita gross domestic product on artificial lighting," said Tsao. "This is so for England in 1700, in the underdeveloped world not on the grid and in the developed world using the most advanced lighting technologies. There may be little reason to expect a different future response from our species."

The bottomline is: Every new increase in efficiency did not lead to a reduction in energy consumption, but to an increase in the overall light output. In the case of light bulbs this means that replacing conventional light bulbs with LED ones will not as it is often assumed reduce the energy consumption by light, but in the long run it will increase the usage of light. Simply put - as light is getting cheaper, there is less need to save on using it. People may start to leave the light on on the porch or in the staircase out of convinience, safety concerns or to keep indoor plants healthy.
Of course the future is hard to predict, but that trend in the reaction of society to improved efficiency is visible in the past 300 years, according to the study.

Researcher Jerry Simmons points out, "More fuel-efficient cars don't necessarily mean we drive less; we may drive more. It's a tension between supply and demand. So, improvements in light-efficient technologies may not be enough to affect energy shortages and climate change.