Actor Matthew McConaughey hawks one device in television commercials in a folksy twang.

Power utilities are signing exclusive deals with manufacturers.

Online tech forums are awash in discussions over different devices’ virtues.

More than five years after smart thermostats were introduced as an easy-to-use alternative to the current programmable models, manufacturers are reporting triple-digit sales increases.

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The thermostats are pitched as the next “it” device and a revolutionary step in getting households to better manage their electricity use.

Parks Associates, a Dallas market-research firm, estimates about 1 in 10 U.S. homes with a broadband connection now has a smart thermostat.

That has driven what is now an $86 million-a-year global market, which may grow to $1.4 billion by 2020, according to a report published last year by Navigant Research.

“Six (million) to 8 million thermostats are sold annually, and in the future a larger and larger portion of those are going to be smart,” says Tom Kerber, director of energy research for Parks Associates. “Think about automatic door locks. They used to be only on Cadillacs. But it moved down to the lower-tier cars. And now you can’t buy a car without automatic locks.”

With more than two dozen models available, smart thermostats vary in features.

But the basic principle is a wall-mounted thermostat that, through sensors and algorithms, learns the patterns of a home’s occupants to cut down on wasteful heating and cooling when no one’s there.

Add in user-friendly interfaces that can be controlled via smartphone and deals with utilities to automatically adjust thermostats in power shortages, and the devices are purported to reduce electricity bills by as much as 20 percent.

Probably the best known device is Nest. Developed by two former Apple executives, Nest was introduced in 2011 at the jaw-dropping price of $400. Some traditional thermostats sell for less than $50.

Nest has since lowered its price to $250 and is estimated to sell about 50,000 units a month, according to Forrester Research.

Its simple design and functionality have proved a big hit with users — not to mention piqued the interest of Google, which bought Nest for $3.2 billion in January.

“Before with the old thermostat, I had to write stuff down and remember what I did the previous day in order to program it,” says Dan Sanchez, a Texas software developer.

The Nest thermostat “has worked really good so far. At first we let it learn our habits, and when we leave the house it doesn’t keep the system on as much.

And if you’re going to be home early, you can use the iPhone app to turn it on before you come back home.”