Smart Thermostats Get Thumbs Up from BPA
June 14, 2017
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Two "learning thermostats," including the Nest, join Bonneville's portfolio of approved energy efficiency tools for the Northwest.
Hundreds of thousands of Northwest homes will be eligible to get brainier while saving money and electricity now that BPA has added two models of smart thermostats to its list of approved energy efficiency products.
BPA promotes energy efficiency by providing technical support and financial reimbursement to 142 public utilities around the four-state region for a portfolio of qualified improvements that save power in homes and businesses in its partner utilities' service areas. The products range from light bulbs to appliances to heating and cooling systems.
Compared to previous generations of programmable thermostats, smart thermostats offer greater benefits and less effort to use effectively after set-up. Devices such as the Nest and Ecobee, the two on BPA's list, learn their household's preferences and schedules to operate the heating and cooling system in the most comfortable, efficient pattern to complement the residents' habits.
To vet the new technology's potential in some Northwest households, BPA partnered with Franklin Public Utility District to test the Nest from 2013 to 2015. The pilot program installed and evaluated smart thermostats in 176 homes in Pasco, Washington, Franklin PUD's service area.
Each was a single-family home that had Wi-Fi and an air-source heat pump without advanced controls. The majority of the homes were less than 2,000 square feet, and half were built after 1979.
The Nest not only proved its worth, it revealed some extra value to the type of heat pumps common in many of the region's homes. The Nest controlled the heat pump's standard cycle to wring out more efficiency.
"One of the things it does is make the individual cycle times run longer," says BPA's Phillip Kelsven, an economist and EE planner. "The average heat pump cycle time was 15 minutes, but after installation of the Nest, it doubled and ran about 30 minutes."
The homes in the pilot project saved an average of 12 percent in their electricity consumption for heating and cooling (841 kilowatt-hours), reducing their total electricity use by 4 percent.
Homes that used more electricity before getting the Nest saw more energy savings. And households that used lower heating set points, higher cooling set points and more aggressive settings also achieved more savings.
The residents were generally happy with the devices, based on a survey. Most households were satisfied with the Nest's usability and the level of comfort it provided. Nearly 90 percent of participants indicated they were "somewhat" or "completely" satisfied, and 75 percent said they were "somewhat" or "completely" likely to recommend the smart thermostat.
A significant minority of participants did mention issues or complications with using the Nest at some point. Many involved Wi-Fi (14 percent) and tended to reflect challenges with household internet connectivity unrelated to the thermostat.
Another 12 percent said they weren't able to make adjustments to the settings whenever they wished. A common complaint was that the "auto-away" setting imposing itself to turn off the HVAC system when people were actually at home. This occurred when residents didn't trigger the occupancy sensor for a period of time by moving around near the thermostat - for example, if they were working in a home office away from the central area. The Nest does offer additional sensors that can be mounted in other zones of the home, which would address that problem.
BPA's Kelsven, Robert Weber and Eva Urbatsch published a paper on the pilot last November, and presented their findings at a 2016 conference of the American Council for an Energy-Efficient Economy. Engineer Tom Osborn and others from BPA teamed with Franklin PUD's Todd Blackman and CLEAResult's Bruce Manclark and Mark Jerome on the project.
While the study focused on air-source heat pumps, which account for the systems in about 40 percent of homes in BPA's territory, Kelsven says smart thermostats can offer value in other homes, as well. "It's also a good complement to forced-air furnaces, either gas or electric," he says. "It's probably going to offer a lesser percentage of savings (compared to homes with air-source heat pumps), but still a good savings."
BPA's decision to approve the Nest and Ecobee for incentives was in step with another development this spring. In March, the EPA designated the Nest thermostat an ENERGY STAR product, making it the first thermostat to receive the certification since regulators announced they were taking it off all programmable thermostats in 2009. Currently four other manufacturers have earned the ENERGY STAR certification for smart thermostats.
As a March article in the publication Utility Dive pointed out: "Home comfort has come a long way in decades, evolving from a ubiquitous circular dial on the wall - how many parents shouted, "Don't touch the thermostat!" - to smart devices that know your work schedule, pre-heat your home and help save energy."
An additional perk: Smart thermostats are compatible with not only smartphones, but the increasingly popular voice-operated speakers such as the Amazon Echo and Google Home.
"We believe these intelligent thermostats are only the beginning of a new generation of smart communicating products that will improve the homeowner experience, energy savings, comfort and security," says BPA's Robert Weber, engineering technical lead.
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