Heat Pump vs Furnace Savings Calculator

Introduction

Choosing between an electric heat pump and a fuel-burning furnace often comes down to one question: what will it cost to heat my home each year? This calculator compares estimated annual operating costs using a simple energy-balance approach. You enter your annual heating load (how much heat your home needs), your heat pump’s average seasonal COP, your furnace efficiency, and your local energy prices. The output shows the estimated yearly cost for each system and the difference (savings).

The results are meant for planning and “what-if” comparisons. They are not a substitute for a full HVAC design, a Manual J load calculation, or a contractor quote. Still, a quick cost comparison can help you decide whether to explore a heat pump, a high-efficiency furnace, or a dual-fuel setup.

How to Use the Calculator

1. Enter your annual heating load in kWh of heat delivered to the home. If you don’t know it, start with an estimate and test a few values.
2. Enter an average seasonal COP for the heat pump (for example, 2.5–4.0 for many air-source systems, depending on climate and equipment).
3. Enter your electricity price in $/kWh (ideally your all-in average rate including delivery charges).
4. Enter your furnace efficiency as a percent (AFUE is commonly used as a proxy for seasonal efficiency).
5. Enter your fuel cost as $ per kWh equivalent of fuel energy. If your bill is in therms, gallons, or liters, convert to kWh-equivalent first.
6. Select Calculate Savings to see annual costs and the savings difference. Use Copy Summary to copy a short comparison.

Key Inputs You Can Adjust

• Annual Heating Load (kWh) — Total heat required over a year, expressed as kWh of heat delivered to the space.
• Heat Pump COP — Coefficient of performance: heat output divided by electrical input (higher is better).
• Electricity Cost per kWh ($) — Your retail electricity price from your utility bill.
• Furnace Efficiency (%) — Fraction of fuel energy converted into usable heat (for example, 80%–98%).
• Fuel Cost per kWh Equivalent ($) — Fuel price expressed per kWh of fuel energy so different fuels can be compared on the same basis.

Cost Formulas and Assumptions

The calculator treats your heating load as a single annual number and assumes constant average performance for each system. That makes it easy to compare options, but it won’t capture hourly weather, defrost cycles, thermostat setbacks, duct losses, or time-of-use pricing.

Heat pump annual cost

Electrical input energy is estimated as heating load divided by COP:

Annual heat pump cost is then:

Furnace annual cost

Furnace efficiency is entered as a percent and converted to a decimal: Eff = Furnace efficiency (%) / 100. Fuel input energy is estimated as heating load divided by efficiency.

Comparing savings

The calculator reports both annual costs and the difference: Annual savings = Furnace cost − Heat pump cost. A positive value means the heat pump is cheaper to operate for the inputs provided.

Worked Example (Quick Check)

Suppose your home needs 12,000 kWh of heat per year. Your heat pump averages COP 3.0, electricity costs $0.15/kWh, your furnace is 90% efficient, and your fuel costs $0.09 per kWh equivalent.

• Heat pump input: 12,000 / 3.0 = 4,000 kWh → cost: 4,000 × 0.15 = $600
• Furnace fuel input: 12,000 / 0.90 ≈ 13,333 kWh → cost: 13,333 × 0.09 ≈ $1,200
• Estimated savings: $1,200 − $600 = $600/year

If a heat pump installation costs $4,000 more up front, a simple payback estimate would be about $4,000 ÷ $600 ≈ 6.7 years. This is a simplified payback and does not include maintenance, financing, or future energy price changes.

Interpreting Results and Practical Notes

If the heat pump looks cheaper, it usually means your electricity price and COP combination beats your fuel price and furnace efficiency combination. If the furnace looks cheaper, it may indicate expensive electricity, a low seasonal COP (very cold climate or undersized/older equipment), or relatively cheap fuel. When results are close, consider non-energy factors such as comfort, noise, cooling needs, emissions, and available rebates.

Typical Scenarios (Rule of Thumb)

Fuel Price Conversion Tips (So the Comparison Is Fair)

The field Fuel Cost per kWh Equivalent is the most common place people get stuck, because utility bills rarely show fuel in kWh. The goal is to express your fuel price as dollars per kWh of fuel energy (not per kWh of delivered heat). Once you do that, the furnace cost formula can correctly account for efficiency.

If you already have a bill that shows energy content, use that. Otherwise, you can convert using typical energy content values. The exact number varies by region, blend, and meter conditions, but these are good planning approximations:

• Natural gas: 1 therm ≈ 29.3 kWh of fuel energy. If gas is $1.50/therm, then fuel cost ≈ $1.50 ÷ 29.3 ≈ $0.051/kWh.
• Propane: 1 gallon ≈ 26.8 kWh. If propane is $3.00/gal, then fuel cost ≈ $3.00 ÷ 26.8 ≈ $0.112/kWh.
• Heating oil: 1 gallon ≈ 40.7 kWh. If oil is $4.00/gal, then fuel cost ≈ $4.00 ÷ 40.7 ≈ $0.098/kWh.
• Wood pellets (bagged): energy content varies widely; use supplier specs if available and convert to kWh per bag or per ton.

After converting, enter the result in the fuel field. Then set Furnace Efficiency to match your equipment (for example, 80% for older non-condensing furnaces, 90–98% for condensing gas furnaces, and often 82–88% for many oil systems). If you are comparing a boiler, you can still use the same approach as long as the efficiency you enter reflects seasonal performance.

What Heating Load Means (And How to Estimate It)

The Annual Heating Load is the total heat your home needs over the year, expressed as kWh of heat delivered indoors. If you have a smart thermostat, an energy audit, or a prior heat-loss model, you may already have a good estimate. If not, you can still get a reasonable starting point using one of these methods:

• From past fuel use: convert last year’s fuel consumption to kWh of fuel energy, multiply by your furnace efficiency to estimate delivered heat. Example: 800 therms × 29.3 kWh/therm ≈ 23,440 kWh fuel; at 90% efficiency, delivered heat ≈ 21,100 kWh.
• From past electric resistance heat: if you heated with baseboards or a space heater, delivered heat is close to electric use (1 kWh in ≈ 1 kWh heat). Adjust if you also used wood or supplemental heat.
• From a rough intensity estimate: some homes fall in the range of 30–120 kWh of heat per square meter per year depending on insulation and climate. This is a broad range; use it only for early planning and then refine.

If you are unsure, try multiple loads (for example 8,000; 12,000; 18,000 kWh) and see whether the conclusion changes. When the conclusion flips depending on load, it usually means the decision is sensitive to assumptions and you should refine the inputs.

Understanding COP and Seasonal Performance

COP (coefficient of performance) is not a fixed number in real life. It changes with outdoor temperature, indoor setpoint, humidity, defrost cycles, and how well the system is sized and installed. A “seasonal COP” is an average across the heating season. If you only know a rating like HSPF or SCOP, you can still approximate a seasonal COP, but the mapping depends on the standard and test conditions.

For planning, many modern cold-climate air-source heat pumps can average around COP 2.0–3.5 depending on location. Ground-source (geothermal) systems can be higher, but installation costs differ. If you want to stress-test the decision, run the calculator with a conservative COP (for example 2.2) and an optimistic COP (for example 3.2) to see the range of possible outcomes.

Beyond Energy Cost: What This Calculator Does Not Include

Operating cost is important, but it is not the only factor in a heating decision. This page intentionally focuses on energy cost so you can compare systems on a common basis. In practice, you may also want to consider:

• Cooling value: a heat pump can provide air conditioning, which may offset the cost of a separate AC system.
• Demand charges and time-of-use rates: if your utility charges more during peak hours, the effective electricity price can be higher than your average.
• Fixed customer charges: keeping a gas connection for a furnace can add monthly fees even if you use little gas.
• Backup heat strategy: some homes use electric resistance backup, a furnace, or a wood stove for extreme cold events.
• Comfort and distribution: duct sizing, airflow, and zoning can matter as much as equipment efficiency.
• Emissions and grid mix: the environmental impact depends on your local electricity generation and fuel source.

Use the calculator as a first pass, then refine with local rates, contractor proposals, and any rebates or tax credits available in your area.

Limitations

• Average COP: real COP changes with outdoor temperature, defrost, and system design.
• Distribution losses: duct leakage or hydronic losses are not modeled.
• Rates and fees: time-of-use rates, demand charges, and fixed customer charges are not included.
• Maintenance and lifespan: energy-only comparison; service costs and replacement timing are excluded.

Disclaimer

This calculator is for informational and educational purposes only. Results are estimates based on simplified formulas and user inputs. Confirm major equipment decisions with a qualified HVAC professional and your local utility tariff details.