Heat Pump Savings Calculator accuracy and testing

Formula source

• Current cost = fuel units x fuel price. Heat pump cost = current delivered heat / COP x electricity rate. Savings = current cost - heat pump cost.

Test cases

Known limitations

• This page documents the checked-in calculator logic and does not certify results for every real-world edge case.
• Use the result as a planning estimate unless the calculator page states a stricter purpose.

Assumptions

• All prices, rates, taxes, and usage values are entered by the user.
• Calculations run locally in your browser and are not stored by Calwarden.
• This is planning math, not financial, tax, engineering, or legal advice.

Unit handling

• Current Annual Fuel Use accepts values in units/yr.
• Fuel Price accepts values in $/unit.
• Fuel Energy Equivalent accepts values in kWh/unit.
• Existing System Efficiency accepts values in %.
• Heat Pump Seasonal COP accepts values in COP.
• Electricity Rate Preset accepts one of the configured options.
• Electricity Rate accepts values in $/kWh.
• Estimated Annual Savings is displayed as currency.
• Current Heating Cost is displayed as currency.
• Heat Pump Heating Cost is displayed as currency.
• Estimated Heat Pump Use is displayed in kWh/yr.

Rounding rules

• Number displays use up to 2 decimal places in the calculator UI.
• Currency outputs are displayed with standard US dollar formatting.
• Input precision follows configured step values where provided.

Version history

Change log