EcoSmart Stud 
Smart thermostats are everywhere – programmable thermostats have been around for a long time, smart thermostats have changed the game with learning capabilities, mobile control, and energy-saving insights. Both units promise to lower your energy bills by changing the temp when you’re at work or home – sleeping or awake. I have set some well-thought-out schedules to save money, and I am not sure those savings ever materialized.
But do smart thermostats save money? That was the question I wanted answered when I moved into a newly constructed home in spring 2018.
Tracking Smart Thermostat for Energy Savings
When I moved into this newly constructed home in the spring of 2018, I installed an energy monitor to keep track of energy usage and solar power production. I set my programmable thermostat and started collecting data. Summer was interesting to watch, but that is relatively low on the energy consumption meter because of the insulation of the home and shading of the eastern and southern windows.
The real test came in winter.
Heat Pump Woes and Thermostat Trouble
My home’s heating setup included a dual-fuel system with an electric heat pump and gas backup. When colder temperatures rolled in, I noticed the system was running constantly even when it shouldn’t have been. After contacting my installer, I learned a surprising truth: changing temps too much with a smart thermostat wastes energy. The heat pump simply didn’t have enough BTUs to raise the temperature quickly like a traditional gas furnace.
After three years of collecting data, I still wondered about the heating season. Summer was not an issue – the house was Net Zero from about March to October. Enter the next HVAC person who knew even more about heat pumps. His advice is to set the temperature and not change it by more than 1-2 degrees total throughout the day or pick a temperature and leave it alone. That BTU term surfaced again! You use a lot of energy to heat a home after it cools down over night. For gas furnaces, it’s not a problem. My gas backup is 80,000 BTUs. My heat pump when it’s in the 20s is 4,000 BTUs. It’s not enough to change the temperature quickly, but enough to hold it constant. He also stated that constantly changing temps up and down actually WASTES energy, not save it. What!?!
Smart Thermostat for Energy Savings: Real Data
Game on! I have three years of data.The HVAC pro adjusted the heat pump/gas changeover from 20 to 30 degrees. I set the temp for 70°F during the day and 69°F at night in December, January, and February. It’s hard to break old habits. For October, November, March, and April, a set 70°F, no changing. We set it down lower (winter) or higher (summer) if we are gone for several days, and no one is home.
After year two of monitoring, here’s what I’ve learned:
- December, January, and February, when I know we are pretty much running on gas, a toss-up. No clear winner. Savings swings 2-8% either way.
- Shoulder months of October, November, March, and April, hands down, keeping that set temp is up to a 40-50% savings winner!
So, do smart thermostats save money? The answer: Yes, but only if you use them correctly—especially with heat pumps.
Smart Thermostat and HVAC System Design
However, there is a caveat to this ongoing test. Enter the heat pump expert. My original heat pump system was not correctly sized! It was sized for a warmer climate, and that is why if the changeover between the gas furnace and electric heat pump is set below 30 degrees, it doesn’t work correctly. There are not enough BTUs for the level of insulation of the home in the cold winter months, and the heat pump runs too much, using considerably more energy than if it changes to the gas furnace.
The design of my system was in 2017, and it was installed in 2018. Six years later, a lot has changed and today, smart thermostats are more sophisticated. Heat pumps are becoming more common, and the training has gotten better for the industry.
But there is still a BTU issue; there is no way around it, even with a cold weather system correctly sized. So, when you get that brand-new heat pump installed, keep the temperature a lot more consistent. Your wallet will thank you.
If you have a gas furnace so far I haven’t found any evidence that supports big changes in temps on a daily basis to save any money.
Smart Thermostat Tips for Energy Savings
Here’s what I recommend after years of testing:
1. Set and Forget
Keep your thermostat set at a consistent temperature. Adjust only by 1–2 degrees max throughout the day.
2. Limit Manual Overrides
Avoid the temptation to constantly adjust temperatures. The less fluctuation, the more efficient your system operates.
3. Use Away Mode Wisely
Use vacation or away mode only when you’re gone for several days—not for quick trips to the grocery store.
4. Know Your System
Understand if your HVAC system uses a heat pump, gas furnace, or dual fuel setup. Your thermostat strategy should match your heating source.
5. Avoid Large Swings in Cold Weather
Heating up a cold house uses more energy than maintaining a steady temperature.
The Smart Choice Isn’t Always What You Think
Smart thermostats are marketed as a one-size-fits-all energy-saving solution. But real-world use reveals more complexity. If your home uses a heat pump especially in colder climates it’s better to keep your thermostat steady than to rely on dramatic scheduling changes.
Smart thermostats can save money, but only when used correctly and within the right type of heating and cooling system. For homeowners using a heat pump with a gas backup, like me, the savings are often achieved by maintaining a consistent temperature rather than frequently adjusting the settings.
When used with knowledge and intention, using a smart thermostat can save energy and help you manage your home energy. But don’t believe the hype without understanding your system first.