LED Christmas lights are gaining traction as prices drop and retailers increase the amount of shelf space set aside for the energy-efficient bulbs.

Wal-Mart is devoting half of its shelf space for Christmas lights to LEDs, which can save about 80 percent of the energy consumed by incandescent bulbs and can pay for themselves in two years or less.

Costco isn’t selling any incandescent lights at all, while General Electric — a player in the Christmas light market for more than a century — expects two out of every five strings of lights it sells this year will be LEDs.

A U.S. Department of Energy study found that each year Christmas lights use enough electricity to power 200,000 homes for a year.