After several years of foundering holiday sales for energy-efficient LED lighting, LED manufacturers and retailers reported sales that were surprisingly brisk even during an economic downturn.

Light-bulb maker Osram Sylvania said it doubled its LED sales since last year to between 15 million and 20 million LED units. LEDs can be three times more expensive than conventional incandescent lights, but they use 90 percent less energy, produce less heat and last longer. Some consumers calculate that an average string of LED lights saves enough energy to pay for itself in as little as a year.

Calculations by other independent researchers suggest the break-even point could be two to three years, depending on how long the lights are left on. Regardless of who is doing the math, the upfront cost of LED lighting is almost always worth the investment, especially with more utilities throwing in additional incentives that can range from $2 to $4 per set.

Among the first to switch to LED lights were large corporations and municipalities that stand to save the most. The government swapped out traditional lighting on the National Christmas Tree in Washington, D.C., which now has 37,000 LED lights.

It’s the key notice that the price of the bulbs, they still can be a barrier for some. For example, Amazon.com sells a string of 100 multicolor LED Christmas lights for about $28, while the incandescent equivalent is about $10. Even so, 21 of Amazon's top 25 Christmas-light sales are LED products.