Make your thermostats as smart as you want, but they still can’t be everywhere at once. The hallways and living rooms where thermostats get their temperature awareness may be a cool 72 degrees, but the bedrooms, basement offices and other often-used rooms in the house can be far hotter or cooler. And if people are uncomfortable in the room they’re in, they’ll change the thermostat, destroying all the careful energy efficiency optimizing that smart thermostats from the likes of Nest and Honeywell are supposed to provide.

Ecobee says it has a solution to this problem -- a sleek, touchscreen-controlled thermostat that links to your smartphone, along with temperature and occupancy sensors for the most popular or problematic rooms in the house. As the Toronto-based startup noted in a Tuesday announcement, the ecobee3 platform is the first to be “designed for homes with more than one room.”

The ecobee3 will go on sale in late September for $249, which includes the thermostat and one sensor. That’s comparable to smart thermostats like Nest’s smart thermostat or Honeywell’s Lyric in terms of price, if a bit on the high side with sensors added in. More sensors are available at $79 per pair, up to a possible 32 per thermostat.

But Stuart Lombard, ecobee co-CEO, said that adding just one remote sensor can lead to big improvements, both in managing the relationship between homeowners and their smart home technology, and in collecting the data to fine-tune its automation and predictive analytics. 

“We have hundreds of thousands of units in the field, and our number-one customer complaint was, ‘I have uneven temperatures in my house,’” Lombard said. “We set out to solve that problem.” The installation is fairly simple, with a new thermostat in the usual location, and a sensor in “the room you use the most and want to make sure you’re comfortable when you’re there,” he said.

That sensor tells the thermostat when the room is drifting out of the preferred temperature range, as well as whether or not it’s occupied, both of which help the software adjust heating and cooling to keep that room comfortable, he said. That works in real time, with occupancy sensors helping the system fine-tune its home-vs.-away presets. But it also works over time to learn just when it needs to switch on whole-home heating or cooling to get the room comfortable for a homeowner’s return from work, he said.

“We can do simulations and see how the product will perform, and even adding one remote sensor significantly improves the occupancy detection algorithms,” he noted. “In terms of intelligence, we have things like optimum start -- we learn the way your heating and cooling system performs with respect to weather."

“We’ll either use a little bit more energy, or a little bit less energy” to keep key rooms at the right temperatures, he noted. But more importantly, “it’s meant to help customers, so they don’t have to play thermostat wars,” always trying to guesstimate the result of fiddling with the thermostat to get the basement warm in winter, or the south-facing bedroom cool in summer.

Some other features of note include a wiring design that avoids the issues that can cause thermostats that use “power stealing” to fail prematurely, often in the midst of heat waves or cold snaps, he said. Nest’s thermostat, Honeywell’s Lyric and many others “steal” power from the circuits that control the heaters, AC compressors, fans and other gear in the home to keep their batteries charged and their processors running, he explained.

But those can fail to deliver enough power, particularly when all those circuits are turned on during periods of extreme weather -- the worst time for a thermostat to fail. Ecobee, in contrast, uses the 24-volt “C-wire” terminals common to thermostat wall connections in North America, and offers a power-extender package for those that don’t have one, to allow installers to get power from furnaces and air handlers, he said. (Here’s a video of what an ecobee thermostat installation looks like.)

Ecobee is working with utilities like San Diego Gas & Electric, National Grid, Austin Energy, Pacific Gas & Electric and Southern California Edison, as well as a number of retail energy providers in Ontario, Texas and New England. Like Nest, it has opened its APIs, and now counts about 500 developer partners building applications on the platform, including companies like AutoGrid, Control4, SmartThings Labs and Earth Networks. It’s also OpenADR 2.0b-compliant, providing a utility-to-home energy interface for demand response and other grid-facing energy management tasks.

Home automation may be coming into bloom, with deep-pocketed players like Google and Apple now getting into the business. Greentech Media's Stephen Lacey reported on the $800 million in smart home investments made this summer, a level of investor interest that had not been seen for some time prior. Lombard said he considers ecobee a coequal with Nest and Honeywell in the emerging smart-thermostat-as-home-automation-platform wars. Will the "more than one room" approach add a new dimension to the competition?