Will a Smart Thermostat Pay for Itself?


Most Americans are likely to pay more to heat their homes this year than they did last winter, according to a recent Energy Department report, because of an expected rise in fuel costs. Common theory says that a programmable thermostat can help counteract those high utility bills. But what about the relatively new breed of smart thermostats, including the much-buzzed-about Nest? Do their additional features deliver enough additional energy savings to justify a price tag of $250 or more? The answer may depend more on you than on them.

According to the Department of Energy, consumers can knock as much as 1 percent off their heating bill for every degree they turn back the thermostat when they're not at home for eight hours at a stretch. This sounds great, but most people don't diligently turn the temperature up and down during their comings and goings during the day. That's where a programmable thermostat comes in. Instead of having to physically move a dial or slider to change the temperature, you can set it to lower automatically at the times of day when family members either go to sleep or leave the house. You can customize this by days of the week, as well -- for instance, by setting the thermostat to save energy during the workweek but keep the heat on when you're home over the weekend.

If your work schedule is erratic, perhaps because you do shift work or travel frequently, reprogramming the device every time your schedule changes can be a real pain. Top-end thermostats such as the Honeywell Wi-Fi Smart Thermostat are Wi-Fi-connected, so you can contact them remotely if you're going to alter your routine, even just for a last-minute dinner or late meeting. The Honeywell learns how long it takes to get the temperature back up and kicks on in time to make the house comfortable when you walk in, removing the temptation to crank up the heat. The Nest learns your habits and adjusts the heat based on your usage patterns. It also has a sensor that automatically triggers a drop in temperature when you're out of the house. It may seem like such features would idiot-proof the process and save a lot of money (not to mention energy) in the long run -- certainly that's the claim of the manufacturers. But would you really make back the cost of one of these devices, which both carry a sticker price of $249?

It's hard to talk concrete numbers, because the amount it costs to heat (and cool) a home depends on many factors, including the type, age, and efficiency of the heating system; how well the walls, doors, windows, and ductwork are sealed; and the thermostat's location in the house, among other things. If you have an old, inadequate heating system or your house isn't well-insulated, for example, you probably need a more expensive fix than a $250 thermostat to start seeing significant energy savings. What's more, utility costs fluctuate, and if prices go up significantly this year, you may spend the same amount of money even if you use less energy. Climate also makes a difference. The Energy Department advises that consumers in regions with mild weather will see the most savings.

Real usage studies of smart thermostats are still in their early days. Pacific Gas and Electric Company in California has partnered with Honeywell to do a trial of smart thermostats but hasn't reported final results yet. The Honeywell Wi-Fi Smart Thermostat just entered the market in September, so it hasn't been through a heating season. In a discussion thread on the Nest website, the comments run about 2-to-1 in favor of savings. But some customers not only didn't save money; they actually spent more on energy than they had in prior years. One personal study of the Nest, by a self-described tech, data, and design enthusiast blogging at GetGrok, measured his energy use over the course of two summers. Controlling for differences in outside temperature, he found that his energy consumption dropped enough in the year he used the Nest to recoup the cost of the thermostat, and then some.

The users who seem to benefit most from a smart thermostat are those who used to have a manual thermostat or never properly programmed a previous thermostat. The Environmental Protection Agency's Energy Star program and a research team at Lawrence Berkeley National Lab assert that many Americans with programmable thermostats set them incorrectly -- in some cases just by leaving the clock set to the wrong time -- or don't program them at all, leaving potential energy savings on the table. Using a regular programmable thermostat judiciously can save about $180 a year on household energy bills, according to an Energy Star estimate -- no smart features necessary.

By far the most important piece of the equation is you. An expensive smart thermostat can make the programming process easier, or at least more appealing, and easily adjust to schedule changes. But if you have a relatively consistent routine and the discipline to effectively program a cheap thermostat (Cheapism.com recommends easy-to-use thermostats under $40), you may be able to realize similar savings without spending over $200 more.