The newest Nest learning thermostat is slimmer and smarter

In Consumer Reports' recent report on programmable thermostats, the Nest Learning Thermostat earned a spot on our recommended list, thanks to its clear display, relative programming ease, and Wi-Fi capability, which allows you to control the device from a computer or smart phone. But several programmable thermostats fared better overall in our Ratings. The second-generation Nest, which launches today, comes with several design enhancements and the promise of improved control and compatibility.

The first upgrade is obvious right out of the box, with the 20-percent thinner profile of the new Nest and its all-stainless steel ring that's designed to reflect your wall color. That makes the new Nest very discreet, certainly compared to the bulkier rectangular thermostats that we tested. The Nest's wider outer ring, which you use to set and operate the thermostat, is also easier to handle than the original.

Inside the Nest, hardware tweaks mean the thermostat will now work with 95 percent of low-voltage heating and cooling systems, up from 75-percent compatibility of the original model. "Our mission is to keep people comfortable in their homes while helping them save energy, and with the next-generation Nest Learning Thermostat, we're able to spread that comfort and savings to even more homes—and to help higher-efficiency systems perform the way they were meant to," said founder and CEO Tony Fadell in the news release.

In terms of intelligence, Nest is also announcing today the launch of version 3.0 of its software (which will be delivered automatically to existing customers tonight). New smart technologies include System Match, which enables Nest to make adjustments based on what type of HVAC system you have. For example, if your home uses radiant heat, which is typically much slower than forced-air systems, Nest will learn to turn the heat on earlier so that you can wake up or come home to a warm house.

Under the 3.0 software, the Nest's Auto-Away feature, which automatically turns your system down after your leave the house, has improved its response time from two hours to as little as 30 minutes. And in addition to support on iPhone, iPad, and Andriod smart phones, the new Nest has expanded its mobile app to include Androd tablets, including Nexus 7 and Kindle Fire. Lastly, you can select English, French or Spanish as the default language, a feature also offered on the top-rated model in our programmable thermostat Ratings, the Venstar Color Touch Series T5800, $170.

The second-generation Nest is now available for pre-order at www.nest.com for $250, with shipping set for mid-October. In the U.S., the second-generation Nest thermostat will also be available later this month at Amazon, Apple's online store and in all 1,700 Lowe's stores. The original Nest will be available at Lowe's for $230 while supplies last.

To see a detailed diagram of how the Nest works, read Inside the Nest Learning Thermostat on The New York Times website.

—Daniel DiClerico