Smart Thermostat Savings Calculator
Estimate annual heating and cooling savings from a smart thermostat setback schedule.
Enter system type, setback degrees, hours per day, and monthly bill.
A programmable or smart thermostat saves money by reducing heating or cooling when you are asleep or away. The savings come from one simple relationship: the greater the temperature difference between indoors and outdoors, the faster a home loses heat. Reduce that difference, and heat loss slows — so your system runs less.
The rule of thumb
Each 1 degree Fahrenheit of setback for 8 hours per day saves approximately 1% on heating or cooling costs. This is an EPA and DOE estimate derived from the thermal physics of building heat loss.
Savings fraction = setback_degrees x (setback_hours / 8) x 0.01
Monthly savings = monthly HVAC bill x savings fraction
The formula is linear as an approximation, but actual savings depend on your insulation level, climate, and how efficiently your system re-heats or re-cools after setback. Very well-insulated homes save more from setback; leaky homes save less because the temperature swings happen anyway.
Heating vs cooling
The physics favors heating setbacks more than cooling setbacks. In winter, the temperature difference between a setback home (60 F) and outside (30 F) is 30 degrees versus 70 F (40 degrees difference). In summer, reducing from 72 F to 78 F during peak hours saves less in absolute terms but can be meaningful.
Smart thermostat features beyond scheduling
Smart thermostats also optimize startup time (the thermostat learns how long your system takes to reach setpoint and starts pre-heating or pre-cooling before you need it). Geofencing adjusts temperature based on where you are. Demand response programs with some utilities pay you to allow brief setbacks during grid peak events. The Nest, Ecobee, and similar devices typically report 10-15% total HVAC savings from users, combining scheduling with these features.