What really works: automation beats behavioral nudges
The biggest energy savings from smart thermostats come from automation that responds to whether anyone is home, not from trying to change your habits. A 2025 study of single-family homes in Luxembourg found that occupancy-based automation—where the thermostat turns down the heat when the house is empty—delivered the largest savings, cutting heating energy by 12.9% [1]. That's a meaningful reduction for a typical household, roughly equivalent to skipping a month of heating each year.
In contrast, the same study found that behavioral nudges like real-time feedback and pre-commitment goals (promising to use less energy) produced almost no savings—less than 0.5% [1]. Only one nudge, social comparison (showing you how your energy use compares to neighbors), worked well, saving about 7.6% on average [1]. The takeaway: if you want a smart thermostat to save energy, prioritize one that learns your schedule and adjusts automatically, rather than one that just sends you alerts.
The catch: savings are fragile and depend on your home
Smart thermostat savings aren't guaranteed—they can be easily undermined by everyday behavior and vary hugely based on your home's equipment. The same Luxembourg study showed that a seemingly small habit—opening windows while the heating is on—can erode the savings from eco-nudges from 9.8% down to just 7.6% [1]. That means if you or your family like fresh air, the thermostat's efforts to save energy can be partially wasted.
Your home's insulation and heating system also matter enormously. A 2022 study from Austria found that for a well-insulated single-family home with a heat pump and solar panels (but no battery), a smart energy management system could cut grid electricity use by a dramatic 40.7% [2]. But for the average home without those upgrades, the national-level savings were much more modest—around 7.4% [2]. So a smart thermostat works best as part of a broader energy-efficient home, not as a standalone fix.
Cooling savings can be even larger—but require smart controls
For air conditioning, smart thermostats can save even more energy, but only if they go beyond simple temperature control. A 2021 study showed that using a smart thermostat to control cooling based on thermal comfort (how the temperature actually feels to people, considering humidity and airflow) rather than just the thermostat setting could cut cooling energy by 33% to 47% [4]. That's because you can let the indoor temperature rise a bit on a humid day without making people uncomfortable, saving significant electricity.
This approach uses machine learning to predict indoor temperature and adjust cooling accordingly. The same study found that this method works especially well in sunny homes, where solar heat gain can be factored into the control strategy [4]. So if you live in a hot climate and have air conditioning, a smart thermostat that uses comfort-based algorithms—not just a fixed schedule—can deliver very large savings.
Sources used in this answer
A Simple Physics-Informed Assessment of Smart Thermostat Strategies for Luxembourg’s Single-Family Homes
Occupancy-based automation saved 12.9% on heating in Luxembourg homes; behavioral nudges like social comparison saved 7.6%, but real-time feedback and pre-commitment saved less than 0.5% [1].
Investigating the impact of smart energy management system on the residential electricity consumption in Austria
For well-insulated Austrian homes with a heat pump and solar panels, a smart energy management system cut grid electricity use by up to 40.7%; nationally, average savings were 7.4% [2].
Using Smart-WiFi Thermostat Data to Improve Prediction of Residential Energy Consumption and Estimation of Savings
Smart WiFi thermostat data can improve prediction of monthly gas consumption to within ±8.6% error, enabling detection of savings as small as 5% from home upgrades [3].
Estimating Smart Wi-Fi Thermostat-Enabled Thermal Comfort Control Savings for Any Residence
Cooling energy savings of 33% to 47% are possible using a smart thermostat with thermal comfort control (based on Fanger's model) rather than simple temperature setpoints [4].
Advancements in Smart Thermostat Technology for Enhanced HVAC Energy Management
A review of smart thermostat technology reported energy savings of up to 25% in residential settings and 30% in commercial settings, with user satisfaction improved by remote control features [5].