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.
annual_hvac_cost = 2000degrees_adjusted = 3hours_adjusted = 8
- 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
Ready to run the numbers?
Open Thermostat Savings Calculator