They are sensors the size of thumbs, but they’re helping to save busy hotels a bundle each year on utility bills.

The widgets are part of a new temperature-control system from Honeywell called Inncom. Using interconnected door sensors, thermostats and infrared motion detectors, Inncom can tell whether a guest is in a room and aptly adjust the thermostat without intervention from the hotel staff.

Since Honeywell bought privately held Inncom 15 months ago, it has been on a tear upgrading hotel rooms with its surreptitious systems. Honeywell hopes Inncom will revolutionize the way hotels — and hopefully other businesses — manage their energy consumption.

“If you take a busy hotel with 300 to 400 rooms, they can spend $1 million a year just on energy. We can save them 10 to 15 percent on that energy bill,” said Tom Rosback, vice president of Honeywell’s $2.6 billion Environmental and Combustion Controls Americas business, based in Golden Valley.

On the surface Inncom doesn’t look like much, but its multiple components stay feverishly busy.

Small sensors on each guest door monitor when doors open and close, while software and other tiny sensors constantly scan the room for motion and heat. If a guest is in the room, the system lets the guest set the thermostat. But once the sensors determine that the guest is gone, Inncom’s computerized thermostat automatically resets the room temperature to the hotel manager’s preferred setting. The system’s inner workings are invisible to guests, but the savings can be substantial.

Hotel general managers say they like Inncom, which usually costs $200 to $400 per room, because it’s automatic and can be integrated into a hotel’s property management system at the front desk. Honeywell said the systems are in 1 million hotel rooms worldwide; customers include Sheraton, Four Seasons, Hyatt and DoubleTree. According to Rosback, Inncom “has been growing in the double digits. We want to move it into as many areas as we can.”

That’s why Honeywell is installing 160 systems this year in hotels, dorm rooms and military barracks. Last year, the Grand Hotel Minneapolis put Inncom systems into 140 rooms. Carlson’s Radisson Hotels and Country Inns & Suites have installed Inncom in about 50 of their 550 U.S. hotels over the years, and executives want more.

“The goal would be 100 percent,” said Ted Lorenzi, the Carlson Rezidor Hotel Group’s senior engineering director of engineering. “When the guest checks out of the room, the thermostat goes back to a predetermined setting that is six or seven degrees higher or lower. You don’t have to push a button. It just kind of does this. The thermostat knows exactly what to do.”

‘Save energy seamlessly’

The system will even sense if a room’s balcony door is ajar. The thermostat panel flashes a message to the guest to close the door. If unheeded, the sensors eventually shut off the air conditioner. Lorenzi likes that.

“It lets you save energy seamlessly without affecting a guest,” Lorenzi said. “If the system costs you $400 a room, you can save 20 percent. It normally pays back in four years.”

Rosback said a Carlson expansion is a great opportunity because Honeywell already provides security and fire safety products for the hotel chain. Inncom offers an added layer of business with its temperature-monitoring system.

“We could be a single point of control just by bringing Inncom into Carlson’s $37 billion global brand,” Rosback said.

Inncom, which had $24 million in sales in 2011, is only a small part of Honeywell’s total $15.9 billion automated building controls business, but Wall Street is taking notice. Inncom “really plays to Honeywell’s strengths,” said Edward Jones analyst Christian Mayes.

“Roughly half of Honeywell’s products are involved in improving energy. So this is one more arrow in their quiver,” Mayes said.

Officials at Xcel Energy also said they are impressed with Inncom because of its unrelenting ability to slash energy consumption. “The motion sensors are pretty brilliant,” said Erin Mathe, who reviews Xcel’s energy efficiency programs.

Higher-end systems

Inncom also offers fancier systems for high-end “presidential suites” that can run $1,000 or more per room. Such sensors can automatically turn on lights, shut or open drapes, lower the minibar temperature, and turn on music and fireplaces as soon as the well-heeled guest checks in at the front desk.

For most hotels, however, the real beauty of the system is that it whacks down their energy bills.

Before Kimpton Hotels bought the Grand Hotel in Minneapolis nearly three years ago, “This place was a huge energy drain. But now we are saving money,” said chief engineer Peter Huncovsky, while checking room temperatures on his Inncom monitor inside the hotel server room.

Up on the computer screen popped a rotating 3-D map of the guts of the Grand Hotel. “This shows every guest room from floors six to 15,” Huncovsky said. Squares with different shades of green indicated specific temperatures ranging from 66 to 78 degrees.

Taking a visitor to the nine-room presidential suite where Denzel Washington and former President Jimmy Carter have stayed, Huncovsky noted that Inncom’s software had automatically set the empty suite to an energy-saving 72 degrees.

“It used to be that we left it to housekeeping to set the thermostat in every room,” he said. “Now that doesn’t happen. This is a piece of the whole energy-saving pie.”