HVAC & Water Heater Energy Efficiency Calculator
Compare an existing appliance against a more efficient replacement to estimate annual kWh saved, dollar savings, and avoided CO2 from power draw and duty cycle.
- Choose the appliance Select an "Appliance type" (Water heater, HVAC system, Water pump, Lighting, or Other) to label the comparison.
- Enter current and new power Fill in "Current power" and "New power" in watts. The percent efficiency improvement is computed from the difference between these two values.
- Enter the duty cycle Enter "Use per day" in hours (up to 24) and "Use per year" in days (up to 366) to define how often the appliance runs.
- Set rate and calculate Confirm the "Electricity rate" in $/kWh (defaults to 0.12), then press Calculate to get annual cost savings, energy saved, and the CO2 reduction.
How much money will a more efficient appliance save me per year?
The calculator converts each appliance to annual energy as kWh/yr = (watts x hours/day x days/yr) / 1000, then multiplies the kWh difference between the old and new unit by your electricity rate. For example, replacing a 1500 W unit with a 1000 W unit running 5 hours a day, 365 days a year, saves about 912 kWh, or roughly $110 at $0.12/kWh.
How is the CO2 reduction estimated?
It multiplies the annual kWh saved by 0.92 lb/kWh, the US national grid-average carbon factor (EIA/EPA, roughly 2024). This is a rough national figure: coal-heavy grids such as WV, KY, and WY exceed 1.5 lb/kWh, while renewables-heavy grids like VT, ID, and WA run under 0.5, per EPA eGRID.
What electricity rate should I use?
The field defaults to $0.12/kWh, a typical US residential average, but you should enter your own rate from your utility bill for an accurate dollar figure. Real-world duty cycles also often differ from rated use hours, so verify against utility data when available.