Thermostat Savings Calculator Formula
Understand the math behind the thermostat savings calculator. Each variable explained with a worked example.
Formulas Used
Estimated Annual Savings
annual_savings = annual_hvac_cost * savings_factorSavings Percentage
savings_pct = savings_factor * 100Monthly Savings
monthly_savings = annual_hvac_cost * savings_factor / 12Variables
| Variable | Description | Default |
|---|---|---|
annual_hvac_cost | Annual Heating/Cooling Cost(USD) | 2000 |
degrees_adjusted | Degrees Adjusted(°F) | 3 |
hours_adjusted | Hours per Day Adjusted(hours) | 8 |
savings_factor | Derived value= degrees_adjusted * hours_adjusted / 24 * 0.01 | calculated |
How It Works
Thermostat Savings Rule of Thumb
The Department of Energy estimates you can save about 1% on heating and cooling costs for each degree you adjust your thermostat for 8 hours.
Formula
Savings = Annual Cost x Degrees x (Hours Adjusted / 24) x 1%
This applies to setback (cooler in winter, warmer in summer) during sleep or away periods. A programmable or smart thermostat automates this for consistent savings.
Worked Example
$2,000 annual HVAC cost, thermostat adjusted 3°F for 8 hours/day.
- 01Savings factor = 3 x (8/24) x 0.01 = 0.01 (1%)
- 02Annual savings = $2,000 x 0.01 = $20
- 03Monthly savings = $20 / 12 = $1.67
Frequently Asked Questions
Is this estimate accurate?
The 1% rule is a DOE approximation. Actual savings depend on insulation, climate, heat pump vs furnace, and outdoor temperature. Savings are larger in moderate climates.
Should I turn off my HVAC when away?
For extended absences, yes. For daily schedules, setback (not off) is better. Turning off completely in extreme weather risks frozen pipes or excessive heat buildup.
Do smart thermostats really save money?
Studies show 10-15% savings on heating and 10-12% on cooling from smart thermostats. They learn your schedule and optimize automatically.
Ready to run the numbers?
Open Thermostat Savings Calculator