Heat Pump vs. Gas Furnace Cost Calculator
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Heat Pump vs. Gas Furnace Cost Calculator
Estimate the annual operating cost difference between a heat pump and a gas furnace for heating your home.
Estimated Annual Operating Cost Difference
—
(Positive number indicates savings with Heat Pump)
Understanding Heat Pumps vs. Gas Furnaces & This Calculator
Choosing between a heat pump and a gas furnace for home heating involves considering several factors, primarily their operating costs, energy efficiency, and suitability for your climate. This calculator aims to provide a clear comparison of their annual operating expenses.
Gas Furnaces
Gas furnaces burn natural gas to produce heat. They are known for their powerful heating capabilities, especially in very cold climates. Their efficiency is measured by Annual Fuel Utilization Efficiency (AFUE), where a higher percentage means less fuel is wasted as exhaust. Common efficiencies range from 80% to 98%.
Heat Pumps
Heat pumps don't generate heat directly; instead, they move heat from one place to another. In winter, they extract heat from the outside air (even cold air) and transfer it inside. In summer, they reverse the process for cooling. Their efficiency is measured by the Coefficient of Performance (COP), which is the ratio of heating provided to the electrical energy consumed. A COP of 3.0 means the heat pump delivers 3 units of heat for every 1 unit of electricity used. Heat pump performance can decrease in extremely cold temperatures, hence the climate factor.
How the Calculator Works
This calculator estimates the annual operating cost for each system based on your input:
-
Annual Heating Usage: The total amount of energy your home requires for heating over a year. You can input this in British Thermal Units (BTU) or Kilowatt-hours (kWh). Many energy bills or HVAC professionals can provide this data.
-
Natural Gas Price: The cost of natural gas, typically priced per therm. (Note: 1 therm = 100,000 BTU).
-
Gas Furnace Efficiency: Your gas furnace's AFUE rating (e.g., 95% means 0.95).
-
Electricity Price: The cost of electricity per kWh.
-
Heat Pump COP: The operational efficiency of your heat pump.
-
Climate Factor: Adjusts the heat pump's performance based on your region's typical winter temperatures. A factor of 1.0 represents standard efficiency, while lower values (e.g., 0.5) indicate reduced performance in colder climates where supplemental heat might be needed more often or the heat pump is less efficient.
Calculation Logic:
The calculator performs the following estimations:
-
Gas Furnace Annual Cost:
If Usage is in BTU:
`(Annual Heating Usage in BTU / (Gas Furnace Efficiency / 100)) * (Price per Therm / 100,000 BTU/Therm)`
If Usage is in kWh:
`(Annual Heating Usage in kWh * 3412 BTU/kWh) / (Gas Furnace Efficiency / 100) * (Price per Therm / 100,000 BTU/Therm)`
(Here, 3412 BTU/kWh is a conversion factor)
-
Heat Pump Annual Cost:
If Usage is in BTU:
`(Annual Heating Usage in BTU / COP / Climate Factor) * (Electricity Price per kWh * 3.412 BTU/kWh)`
If Usage is in kWh:
`(Annual Heating Usage in kWh / COP / Climate Factor) * (Electricity Price per kWh)`
(Here, 3.412 BTU/kWh is a conversion factor for electricity price if the usage is already in kWh, ensuring consistent units for calculation)
-
Difference: Gas Furnace Annual Cost – Heat Pump Annual Cost
When to Use This Calculator
Use this calculator if you are:
- Considering installing a new heating system.
- Looking to understand the potential long-term savings of switching from gas to electric (heat pump).
- Comparing the operational costs of existing systems in different homes or climates.
Disclaimer: This calculator provides an *estimate* based on the inputs provided. Actual costs can vary due to installation costs, maintenance, specific equipment models, fluctuating energy prices, home insulation, thermostat settings, and local climate variations. It does not account for the cost of electricity for air conditioning (which heat pumps provide) or the upfront installation costs of either system.
function calculateCosts() {
var annualHeatingUsage = parseFloat(document.getElementById("annualHeatingUsage").value);
var usageUnit = document.getElementById("usageUnit").value;
var gasPricePerUnit = parseFloat(document.getElementById("gasPricePerUnit").value);
var gasFurnaceEfficiency = parseFloat(document.getElementById("gasFurnaceEfficiency").value);
var heatPumpElectricPrice = parseFloat(document.getElementById("heatPumpElectricPrice").value);
var heatPumpEfficiencyCOP = parseFloat(document.getElementById("heatPumpEfficiencyCOP").value);
var climateFactor = parseFloat(document.getElementById("climateFactor").value);
var resultElement = document.getElementById("calculationResult");
resultElement.textContent = "–";
// Input validation
if (isNaN(annualHeatingUsage) || annualHeatingUsage <= 0 ||
isNaN(gasPricePerUnit) || gasPricePerUnit < 0 ||
isNaN(gasFurnaceEfficiency) || gasFurnaceEfficiency 100 ||
isNaN(heatPumpElectricPrice) || heatPumpElectricPrice < 0 ||
isNaN(heatPumpEfficiencyCOP) || heatPumpEfficiencyCOP <= 0 ||
isNaN(climateFactor) || climateFactor <= 0) {
resultElement.textContent = "Please enter valid positive numbers for all fields.";
return;
}
var gasCostAnnual = 0;
var heatPumpCostAnnual = 0;
// Constants
var BTU_PER_THERM = 100000;
var BTU_PER_KWH = 3412.14; // More precise conversion
// Calculate Gas Furnace Cost
var annualHeatingUsageInBTU = 0;
if (usageUnit === "BTU") {
annualHeatingUsageInBTU = annualHeatingUsage;
} else if (usageUnit === "kWh") {
annualHeatingUsageInBTU = annualHeatingUsage * BTU_PER_KWH;
}
var gasUsageInTherms = annualHeatingUsageInBTU / BTU_PER_THERM;
var gasFurnaceActualEfficiencyFactor = gasFurnaceEfficiency / 100;
gasCostAnnual = gasUsageInTherms * (1 / gasFurnaceActualEfficiencyFactor) * gasPricePerUnit;
// Calculate Heat Pump Cost
var heatPumpElectricityConsumptionInKWH = 0;
if (usageUnit === "BTU") {
// Need to convert BTU requirement to kWh equivalent based on heat pump efficiency
// Heat delivered = Electricity consumed * COP
// Heat delivered (BTU) = Electricity consumed (kWh) * COP * BTU_PER_KWH
// Electricity consumed (kWh) = Heat delivered (BTU) / (COP * BTU_PER_KWH)
// We also need to account for the climate factor reducing effective COP
var effectiveCOP = heatPumpEfficiencyCOP * climateFactor;
if (effectiveCOP <= 0) effectiveCOP = 0.1; // Prevent division by zero or negative effective COP
// The formula should reflect the energy needed for the required heat output.
// If the heat pump delivers X amount of heat (BTU), and its COP adjusted for climate is Y,
// then the electricity needed is X / (Y * BTU_PER_KWH).
heatPumpElectricityConsumptionInKWH = annualHeatingUsageInBTU / (heatPumpEfficiencyCOP * climateFactor * BTU_PER_KWH);
} else if (usageUnit === "kWh") {
// If usage is already in kWh, we need to consider the COP and climate factor.
// Heat Pump delivers (kWh * 3412) BTU. This requires (kWh * 3412) / COP / 3412 = kWh input if efficiency were 100%.
// Correct approach: Energy needed for desired heat = Heat Output / COP.
// If annualHeatingUsage is kWh, it implies the required *heat output* in kWh equivalent (often called Heating Season Performance Factor calculation or similar).
// For simplicity and common calculator approach: we assume the Annual Heating Usage is the 'heat delivered' target.
// Heat Delivered (kWh equivalent) = Electricity Consumed (kWh) * COP
// Electricity Consumed (kWh) = Heat Delivered (kWh equivalent) / COP
// We are given Annual Heating Usage, which should be treated as 'heat delivered'.
// If usageUnit is kWh, we assume it's the *energy output* required.
// Electricity required = Heat Output (kWh) / (COP * ClimateFactor)
// If Annual Heating Usage is already in kWh, it represents the *output* energy.
// The input electricity needed would be output / (COP * climateFactor).
// HOWEVER, often 'annual heating usage' in kWh refers to the *electrical input* for an electric resistance heater.
// For this calculator, let's assume Annual Heating Usage is the *target heat output*.
// So, for kWh input, the calculation is:
heatPumpElectricityConsumptionInKWH = annualHeatingUsage / (heatPumpEfficiencyCOP * climateFactor);
}
// Ensure consumption is not negative due to extreme climate factors etc.
if (heatPumpElectricityConsumptionInKWH 0) {
resultElement.textContent = "$" + costDifference.toFixed(2) + " saved annually with Heat Pump";
} else if (costDifference < 0) {
resultElement.textContent = "$" + Math.abs(costDifference).toFixed(2) + " saved annually with Gas Furnace";
} else {
resultElement.textContent = "Costs are approximately equal";
}
}