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Mini-Split vs Propane Calculator: Find Your Switchover Temperature

At What Temperature Does Your Heat Pump Cost More Than Propane, Gas, or Oil?

Answer the #1 question every heat pump owner asks: when should I switch to backup heat? Enter your electric rate and fuel prices to see a real-time cost-per-hour comparison at every outdoor temperature. The calculator finds your exact switchover point — the temperature where propane, gas, or oil becomes cheaper than your mini-split. See live COP curves that show how your heat pump's efficiency drops as it gets colder, and cost-per-hour charts that make the crossover obvious. Works in both Fahrenheit and Celsius with support for natural gas priced by therm, cubic meter, or GJ.

Pro Tip: Start by estimating your home's design heat load from real bills. Use our Heat Load from Utility Bills tool for tighter, more accurate cost comparisons.

Estimate your home's heating load from actual utility bills

Heat Load from Bills Calculator →

Calculate full-year ROI for a heat pump upgrade

Heating Bill ROI Calculator →

Same calculator available in Spanish (Espanol)

Calculadora de Eficiencia Energetica →
Start Using This Tool See How It Works
Mini-Split Efficiency & Cost Calculator
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How It Works

  1. Pick Your Fuel Sources

    Select the fuels you want to compare against the heat pump. Choose from propane ($/gallon), natural gas ($/therm, $/m3, or $/GJ), fuel oil ($/gallon), or electric resistance ($/kWh). You can compare multiple fuels at once.

  2. Enter Your Energy Prices

    Type in your actual electricity rate and fuel prices. Use your latest utility bill for the most accurate numbers. Prices vary wildly by region, so real rates matter more than national averages.

  3. Set Temperatures

    Enter your indoor setpoint (typically 68-72 degrees F) and select the outdoor temperature range you want to analyze. The calculator will generate cost and COP curves across the full range.

  4. Estimate Heat Load (Optional)

    For dollar-per-hour cost comparisons, enter your home's estimated heat load in BTU/hr at design temperature. If you don't know it, use our Heat Load from Bills tool to calculate it from your utility data.

  5. Review Results & Charts

    See the COP vs. temperature curve, cost-per-hour comparison chart, and the exact switchover temperature where the heat pump becomes more expensive than your backup fuel. Use these results to plan your heating strategy by temperature.

Built For

  • Homeowners comparing mini-split heat pump operating costs against their current propane furnace
  • DIY mini-split installers calculating whether a ductless system will save money in their climate
  • HVAC contractors quoting jobs and showing customers the cost advantage of heat pump systems
  • Cold climate heat pump planners identifying the switchover temperature where backup heat kicks in
  • Homeowners on propane evaluating whether switching to electric heat pump makes financial sense
  • Energy auditors comparing fuel options for existing homes during weatherization assessments
  • Landlords evaluating heating system upgrades across multiple rental properties

Features & Capabilities

13 Built-In COP Presets

Choose from manufacturer-specific COP curves for popular cold-climate mini-splits including Mitsubishi Hyper Heat, Fujitsu XLTH, MrCool Universal, and more. Each preset reflects real published performance data at multiple outdoor temperatures.

Custom COP Editor

Define your own COP vs. temperature data points if you have manufacturer specs or field-measured performance data. The calculator interpolates between your points to build a smooth performance curve.

Switchover Analysis

Identifies the exact outdoor temperature where your heat pump costs more per BTU than your backup fuel. Below this temperature, run the furnace. Above it, run the heat pump. This is the number that drives your heating strategy.

Cost vs. Temperature Chart

See operating cost per hour for each fuel source plotted across the full outdoor temperature range. The crossover point is clearly marked so you can make real decisions based on your local climate data.

COP vs. Temperature Chart

Visualize how your heat pump's coefficient of performance drops as outdoor temperature decreases. Understand why a COP of 3.5 at 47 degrees F drops to 1.5 at minus 5 degrees F and what that means for your heating bills.

English & Spanish Toggle

Full bilingual support. Switch between English and Spanish with one click. The Spanish version is also accessible via URL hash (#es) for direct linking and search engine indexing.

Unit Flexibility

Toggle between Fahrenheit and Celsius for all temperature inputs and displays. Natural gas pricing supports therms, cubic meters, and gigajoules to match whatever your utility company uses on your bill.

Comparison

Fuel Source Cost at 40 deg F (example) Cost at 10 deg F (example) Best For
Mini-Split Heat Pump Lowest cost (COP ~3.5) Moderate cost (COP ~1.8) Mild to moderate cold climates, spring/fall shoulder seasons
Propane Furnace Higher than heat pump Often competitive Backup below switchover temp, rural properties without gas
Natural Gas Furnace Higher than heat pump Usually cheapest Primary heat in cold climates where gas is cheap
Fuel Oil Furnace Highest Moderate to high Northeast homes with existing oil infrastructure
Electric Resistance Much higher Highest Emergency backup only - never cost-effective as primary

Frequently Asked Questions

The calculations use real thermodynamic relationships and manufacturer-published COP data. Accuracy depends on the quality of your inputs - your actual electricity rate, fuel prices, and heat load estimate. For planning purposes, this is more than adequate. For final system sizing, always consult with a qualified HVAC installer.
COP stands for Coefficient of Performance. It measures how many units of heat a heat pump delivers per unit of electricity consumed. A COP of 3.0 means for every 1 kWh of electricity, the heat pump delivers 3 kWh worth of heat. Higher COP means lower operating cost. COP drops as outdoor temperature drops, which is why the switchover temperature matters.
This tool compares operating costs, not system sizing. To properly size a mini-split, you need a heat load calculation based on your home's square footage, insulation levels, window area, and climate zone. Use our Heat Load from Bills calculator to estimate your BTU/hr requirements, then match that to mini-split capacity ratings.
Yes. The COP presets include cold-climate models like Mitsubishi Hyper Heat that are rated down to minus 13 degrees F. The calculator shows how costs change even at extreme cold temperatures, so you can plan your backup heating strategy for the coldest nights.
Yes, for any real installation. This calculator helps you understand the economics before you call a contractor. Use it to ask better questions, evaluate quotes, and understand whether a heat pump makes financial sense for your specific situation and energy prices.
The switchover temperature is the outdoor temperature at which your heat pump and your backup fuel cost the same per BTU delivered. Above this temperature, the heat pump is cheaper. Below it, your furnace or boiler is cheaper. Knowing this number lets you set your thermostat controls to automatically switch between systems at the right time.
Yes. Use the custom COP editor to enter COP values at specific outdoor temperatures from your unit's spec sheet or field measurements. The calculator interpolates between your data points to build a complete performance curve.
Most cold-climate mini-splits remain more cost-effective than propane or oil down to 15-25 degrees F, depending on your local electricity and fuel prices. The COP drops as temperature drops - a typical cold-climate unit delivers COP 3.5 at 47 degrees F but only COP 1.5 at minus 5 degrees F. The exact crossover depends on your specific fuel prices. Use the switchover analysis in this calculator to find the precise temperature for your situation. Below the switchover temperature, your backup furnace or boiler is cheaper to run.
At 47 degrees F with a COP of 3.5 and electricity at $0.15/kWh, a 24,000 BTU mini-split costs roughly $0.30-0.40 per hour to run. At 17 degrees F with COP around 2.0, that rises to $0.55-0.70 per hour. At 0 degrees F with COP around 1.5, expect $0.80-1.00 per hour. These numbers vary significantly with your electricity rate, system efficiency, and heating load. Enter your actual rates into this calculator for precise hourly costs at every outdoor temperature.
In most cases, yes - especially at moderate temperatures. With propane at $2.50/gallon and electricity at $0.15/kWh, a mini-split is typically cheaper above 15-20 degrees F. Below that, propane can be cheaper as the heat pump COP drops. The exact switchover depends on your propane price, electricity rate, furnace efficiency, and heat pump model. This calculator shows you the cost comparison at every temperature so you can make a data-driven decision rather than guessing.
Disclaimer: Cost estimates are based on the energy prices and COP data you provide. Actual operating costs vary with weather patterns, equipment condition, installation quality, duct losses, and utility rate structures. This tool is for planning and comparison purposes. Always verify with a qualified HVAC installer before making purchasing decisions.

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