Homeowners who live in areas without natural gas service often consider switching their heating system to propane. While it is possible to convert many natural gas furnaces to propane, the process is complex, technical, and requires licensed expertise. Propane operates at a higher pressure and contains far more energy per cubic foot than natural gas. Because of this, the furnace must be equipped with different burner orifices, properly calibrated gas valves, new regulator components, and updated labeling.
When performed correctly by a licensed HVAC technician, a conversion can deliver safe and reliable heating. When performed incorrectly—or attempted by an untrained homeowner—it can result in severe overfiring, equipment damage, carbon monoxide leaks, or explosion hazards.
This guide explains the full professional process, the technical differences between fuels, code requirements, cost considerations, and how to decide whether conversion or replacement is the better long-term choice.
Understanding Why Natural Gas and Propane Require Different Furnace Setups
Natural gas and propane burn differently because of their pressure characteristics, fuel density, and combustion needs. Propane contains nearly double the energy content of natural gas, meaning a furnace designed for natural gas will release too much fuel if operated on propane. This isn’t simply inefficient—it’s genuinely dangerous, causing excessive flames and overheating inside the heat exchanger.
The American Gas Association notes that fuel-specific burner sizes, regulators, and pressure settings are required for compliant operation. Furnace manufacturers design conversion kits for models that are certified to operate on both natural gas and propane, and these kits include the precise components needed to ensure proper combustion.
Newer gas furnaces are more likely to be compatible with propane conversion kits, making them a more viable option for homeowners considering this switch. Using manufacturer-approved conversion kits can help maintain a furnace’s warranty, ensuring long-term reliability and compliance.
Key Differences Between Natural Gas and Propane Furnaces
Understanding these key differences is essential before diving into the detailed comparison shown in the table below, which highlights how natural gas and propane furnaces vary in their components and operation.
| Feature | Natural Gas Furnaces | Propane Furnaces |
|---|---|---|
| Burner orifice size | Larger | Smaller |
| Manifold pressure | Lower | Higher |
| Required regulator | NG-rated | LP-rated |
| Fuel energy density | Lower | Higher |
| Combustion air requirements | Higher volume | Lower volume |
| Safety risk if mismatched | Underfiring or unstable flame | Severe overfiring, CO risk, fire hazard |
Understanding these differences helps homeowners appreciate why conversions must never be improvised.
The Professional Conversion Process
Converting a natural gas furnace to propane involves several technical steps that require specialized tools and fuel-handling certifications. Specialized tools such as a manometer, combustion analyzer, electronic gas detector, and specific wrenches are required for the conversion process.
Below is an overview of how qualified technicians perform conversions; however, this is not guidance for homeowners to do the work themselves.
How Licensed Technicians Perform the Conversion
1. Shut down and isolate the system
Power is turned off at the disconnect or breaker, and the natural gas supply is closed. The technician verifies zero gas flow before beginning work.
2. Replace the burner orifices
Propane requires smaller orifices to restrict fuel flow. The technician installs the model-specific orifices included in the approved conversion kit.
3. Adjust or replace the gas valve
Propane operates at a higher manifold pressure. The technician uses a manometer to calibrate the valve, replace springs, or install a propane-rated valve as specified by the manufacturer. The typical gas pressure for propane is around 10-11 inches of water column, compared to natural gas’s 3.5 inches, highlighting the need for precise adjustments during conversion.
4. Install the updated rating plate
Manufacturers require a furnace to be relabeled with the correct propane specifications to ensure safe servicing in the future.
5. Connect propane supply piping
The natural gas line is capped, and the furnace is connected to a propane tank using approved piping and regulators supplied by a propane professional.
6. Test the system for leaks and proper combustion
Finally, the unit undergoes flame analysis, pressure verification, ignition testing, and safety control checks. The Consumer Product Safety Commission recommends post-conversion CO testing and leak checks for any fuel-burning appliance.
Combustion analysis should be performed to measure carbon monoxide, oxygen, and carbon dioxide levels to ensure safe and efficient burning after conversion.
Each step ensures safe operation and compliance with mechanical and fuel-gas codes.
Why Homeowners Should Never Attempt Conversion Themselves
Before attempting such a conversion, it is important to understand the serious risks and potential hazards involved, including the following critical safety concerns:
- Incorrect orifice sizing can cause extreme over-firing
- Fuel pressure mis-adjustments may lead to propane leaks
- Incomplete combustion can release carbon monoxide
- Ignition failure may create delayed ignition or flashback hazards
- DIY conversion voids furnace warranties and violates mechanical codes
- Specialized tools such as combustion analyzers and manometers are needed
For ongoing efficiency and safety, see Furnace Maintenance. If a propane leak is suspected, one should evacuate the area immediately and contact emergency services. Prompt action can prevent serious accidents and ensure the safety of all occupants.
The Cost of Converting a Natural Gas Furnace to Propane
Conversion costs vary based on furnace age, model availability, and the complexity of the gas valve adjustments. While the conversion kit itself is usually affordable, the total cost depends on whether additional components—such as a new valve, regulator, or ignition parts—are required. The initial conversion cost for switching to propane can be substantial, including expenses for conversion kits and new components.
Typical Costs for Natural Gas to Propane Conversion
| Item | Estimated Cost Range |
|---|---|
| Manufacturer LP conversion kit | Low to moderate |
| Gas valve replacement (if needed) | Moderate |
| Labor for conversion | Moderate |
| Propane tank installation (separate provider) | Moderate to high |
| Post-conversion inspection | Low |
For older furnaces, homeowners often find that the combined cost of converting and updating worn components approaches the price of installing a new propane-ready furnace. In these situations, replacement may offer greater long-term value.
Understanding Propane Supply, Storage, and Fuel Delivery Requirements
Switching from natural gas to propane involves more than modifying the furnace; it requires proper propane storage, delivery, and regulation. Unlike natural gas delivered through pipelines, propane is trucked and stored in on-site tanks that must meet safety setback requirements.
Propane is significantly more hazardous than natural gas because it tends to pool, increasing the risk of fire or explosion if leaks occur. Installing safety devices such as gas detectors and shut-off valves is crucial during propane conversion to guarantee safe and secure operation.
Tank size affects heating costs, with larger tanks enabling lower fuel prices. Reliable supply depends on working with a reputable local propane dealer offering automatic delivery and monitoring.
Correct installation of vaporizers, regulators, and piping ensures proper fuel pressure to the furnace. Improper setup can cause ignition issues or inconsistent operation, so professional sizing and installation are essential for stable performance and to avoid misdiagnosed furnace problems.
Combustion Tuning and Post-Conversion Performance Optimization
After converting a natural gas furnace to propane, the final crucial step is tuning the combustion system for optimal performance. Technicians use combustion analyzers to adjust the air-to-fuel ratio, preventing soot, flame rollout, and protecting the heat exchanger.
They also inspect draft inducer function, ignition timing, burner cleanliness, and flame shape to ensure proper operation. Small adjustments to shutter position and regulator settings significantly impact system stability and lifespan.
A well-tuned propane furnace runs efficiently, provides consistent heat, and minimizes carbon monoxide risks. Poor tuning—often from improper DIY work or skipped checks—can cause incomplete combustion, short cycling, fouled burners, or ignition delays.
Regular maintenance helps sustain performance by detecting pressure shifts, ignition wear, and flame changes over time. Propane is an environmentally friendly heating option because it burns cleanly and produces fewer emissions than oil or natural gas.
Choosing Between Converting and Replacing Your Furnace
Before scheduling a conversion, homeowners should consider whether the existing furnace is worth modifying. If the unit is more than 12–15 years old, has a worn heat exchanger, or is no longer under manufacturer warranty, replacement may provide better efficiency and reliability.
Age alone doesn’t determine suitability, but older furnaces often have outdated blower motors, ignition systems, or draft inducer assemblies that may not perform well on propane. Likewise, homes without existing propane infrastructure must account for tank placement, trenching, and code requirements for exterior clearances.
Additionally, a homeowner planning a future heat pump installation or hybrid heating setup might decide that conversion is only a short-term solution. Evaluating the broader heating strategy helps prevent unnecessary investment.
Evaluating the Safety Requirements of Converting to Propane
Operating a furnace with incorrect fuel settings is a well-documented safety hazard. Propane produces higher flame temperatures, and natural gas furnaces are not designed to manage that heat without modified components. Over firing can warp burners, crack the heat exchanger, damage the inducer motor, and overwhelm safety sensors.
A cracked heat exchanger is particularly dangerous because it can allow carbon monoxide into the home’s air supply. The National Fire Protection Association (NFPA) stresses that combustion appliances must be set up and verified according to the fuel they use, with proper pressure regulation and airflow to prevent incomplete combustion.
A professional conversion eliminates these risks by ensuring correct fuel delivery, pressure calibration, ignition performance, and exhaust venting.
Factors That Influence Whether Conversion Is a Good Long-Term Investment
Homeowners evaluating propane as a heating option should consider fuel availability, price stability, and system lifespan. Factors that influence long-term value include:
- The existing furnace’s age and condition
- Local propane pricing and supply agreements
- The cost difference between conversion and replacement
- Expected heating load based on climate
- Tank installation requirements and annual inspections
Propane can offer strong heating performance and independence from natural gas infrastructure, but the economics vary based on region and home design.
For troubleshooting or heating issues, visit our Furnace Repair page.
When You Should Not Convert a Natural Gas Furnace
In some situations, converting a natural gas furnace to propane may not be advisable due to various practical and safety concerns. Consider the following factors that indicate when conversion should be avoided:
- The furnace is older and nearing the end of its lifespan
- No manufacturer-approved LP conversion kit exists
- The heat exchanger shows signs of wear or cracking
- Local code restrictions prevent propane tank placement
- A new propane furnace would offer higher efficiency and lower long-term cost
- The homeowner is planning to switch to a heat pump system in the next few years
Frequently Asked Questions
Is it hard to convert natural gas to propane?
Yes. It requires precise adjustments to gas pressures and fuel-delivery components, along with approved manufacturer parts. Only licensed technicians can legally perform this work.
Is it cheaper to heat your home with natural gas or propane?
Natural gas is usually cheaper where available. Propane may be competitive in rural areas or where fuel contracts reduce cost variability.
What may happen if a natural gas furnace is fired on propane?
It will overfire, producing dangerously large flames, excessive heat, and high carbon monoxide levels. This can crack the heat exchanger and pose explosion risks.
How safe is a natural gas to propane conversion?
A professionally performed conversion is safe. DIY conversions are extremely dangerous and violate fuel-gas codes.
Scheduling Professional Help
If you’re considering converting your natural gas furnace to propane or replacing an existing heating system, Neighborhood Plumbing, Heating, A/C & Electrical can help you determine the safest and most cost-effective solution.
To request an estimate or schedule service, reach out through our Contact Us page.