I installed a smart thermostat two years ago. A Nest. $249 at Home Depot. I expected it to save me money. I did not expect it to save me $287 in the first year. But that is exactly what happened. And I have the data to prove it.
The thermostat learned my schedule. I work from home, but I am in my office from 8 AM to 6 PM. The thermostat learned that and adjusted the temperature accordingly. It set the AC to 78 degrees during the day when I was in the office, then cooled to 74 before I moved to the living room. It pre-cooled the house before I went to bed. It raised the temperature at 5 AM when I was still asleep. All automatically. All without me touching it.
The savings came from three things. First, the automatic scheduling. My old thermostat stayed at 74 all day. The smart thermostat let it drift to 78 for 8 hours. That saved about $12 a month. Second, the away detection. If I left for errands, the thermostat sensed my phone was gone and raised the temperature. That saved another $8 a month. Third, the time-of-use optimization. My utility charges more from 2 PM to 8 PM. The smart thermostat pre-cooled before 2 PM and coasted through peak hours. That saved $6 a month.
Total monthly savings: $26. Annual savings: $312. Minus the $249 cost, my payback was 9.6 months. Every month after that is pure savings. And the comfort is better too. I never come home to a hot house. I never wake up sweating. The thermostat just... knows.
But smart thermostats are not magic. They work best if you have a consistent schedule. If you travel constantly, if your schedule is erratic, if you have a large family with conflicting preferences β the learning algorithm gets confused. My neighbor has three kids and a rotating work schedule. His Nest never learned anything. He returned it after six months.
Also, the savings depend on your climate. In Phoenix, where I live, AC is 60% of the electric bill. A smart thermostat that optimizes AC saves a lot. In Seattle, where heating is the primary cost, the savings are smaller. The thermostat still helps. But the payback is longer.
If you have a consistent schedule and high cooling costs, get a smart thermostat. The data is clear. The savings are real. And the comfort improvement is worth the price even without the savings. My $287 first-year savings paid for the thermostat and then some. And this year, I am on track to save $310. It is the best $249 I have ever spent on my house.
I also compared my savings to my neighbor who refused to get a smart thermostat. "Too expensive," he said. "Too complicated." His house is the same size as mine. His AC unit is the same age. His bill last July? $487. Mine? $312. That is $175 in one month. Over the summer, that is $700. His "too expensive" thermostat cost him $700 in one season. And he still thinks he saved money by not buying one.
The other benefit nobody talks about is the data. The Nest app shows me exactly when my AC runs, for how long, and why. I can see that my AC runs 40% less on days when I pre-cool before peak hours. I can see that weekends cost more because I am home all day. I can see that my dog β who stays home while I work β apparently triggers the motion sensor and keeps the AC running. I adjusted the settings. I saved another $15 a month. Data is power. And power is money.
One more thing: the environmental impact. My reduced AC usage means less strain on the grid. Less fossil fuel burned. Less carbon emitted. It is not the primary reason I bought the thermostat, but it is a nice side effect. I am saving money and reducing my carbon footprint by 8% annually. That is not nothing. And in Phoenix, where summer AC is basically a moral dilemma, every kilowatt saved is a small victory.
β David Reynolds, Phoenix, AZ
David is a homeowner who tracks every watt and every degree. He believes in smart thermostats, data, and never coming home to a hot house.
