Natural Gas vs. Propane Garage Heaters: Which Fuel Should You Choose?

Natural Gas vs. Propane Garage Heaters: Which Fuel Should You Choose?

Hey, it’s Samantha! 👋

If you’ve been shopping for a garage or workshop heater, you’ve probably run into the same question over and over again:
Should I go with natural gas or propane?

They’re both reliable fuels, both power similar high-efficiency units, and both can keep your space toasty all winter. But they’re not identical—and the differences can affect your energy bills, installation choices, and long-term flexibility.

Let’s unpack it all clearly so you can make a smart, confident choice for your own setup. And we’ll spotlight the Modine Hot Dawg 75,000 BTU Natural Gas Unit Heater along the way, since it’s designed for either fuel type with a quick conversion kit.

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🔍 The Big Picture: Two Fuels, One Goal

Both natural gas and propane are clean-burning hydrocarbons that produce plenty of heat without heavy emissions.
The key differences come down to how you get them and what they cost over time.

 

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💰 Cost Comparison — Breaking Down the Real Numbers

1. Fuel Price per Heat Output

Let’s look at cost per useful heat unit (1 therm = 100,000 BTU):

• Natural gas: ≈ $1.20 / therm

• Propane: ≈ $2.80 / gallon ≈ $3.05 / therm equivalent

Even accounting for propane’s higher energy content, natural gas usually wins on raw cost. If your home already has a gas line, that pipeline connection keeps your running costs low and predictable (energystar.gov ).

2. Equipment Cost

Most garage heaters—including Modine’s—are available in either NG or LP versions, and the price difference is minimal. The only added cost for propane is the tank and regulator setup, which can range from $500–$2,000 depending on size.

3. Maintenance and Service

Service frequency is nearly identical. Propane systems may need an occasional regulator or line inspection since tanks sit outdoors and face temperature swings (govinfo.gov ).

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🌎 Availability and Convenience

Natural Gas — Set It and Forget It

If your property is connected to a gas main, natural gas is the hands-down winner for convenience. You don’t worry about deliveries or tank levels — you just set the thermostat and go.

Natural gas also pairs well with smart thermostats and zoning systems, making it great for those who want steady, automated control.

Propane — Freedom and Flexibility

For rural homes and workshops off the utility grid, propane offers independence. A tank can sit outside or be buried underground, and refill schedules are straightforward. You choose the size (usually 120 to 500 gallons) based on usage frequency.

Propane’s mobility also lets you take heat where pipelines don’t reach — barns, detached garages, construction sites, and seasonal cabins.

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⚙️ Performance and Heat Output

Energy Density and Combustion

Propane packs a lot of energy into a small volume — about 2.5 times more BTUs per cubic foot than natural gas. But because of burn rate and air mix differences, most modern unit heaters are engineered to deliver comparable efficiency on either fuel.

A typical Modine Hot Dawg runs around 80 – 83 % AFUE (no matter the fuel). That means roughly 80 % of fuel energy turns into heat for your garage.

Cold-Weather Performance

Both fuels perform well in cold weather, but propane has a slight advantage in energy stability at low temperatures. The catch: you must size the tank and regulator properly so the liquid propane vaporizes fast enough to feed the burner.

Natural gas doesn’t require storage, so supply pressure is constant — a big benefit in very cold climates.

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🧩 Environmental Impact

Both fuels emit less CO₂ than heating oil or coal.

• Natural Gas: ≈ 117 lb CO₂ per million BTU

• Propane: ≈ 139 lb CO₂ per million BTU, but no methane leaks on-site

So propane burns cleaner at the point of use, while natural gas has a smaller carbon footprint from production to consumption if the system is tight.

For most homeowners, the difference is slight — you’re already making a greener choice than oil or wood.

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🔄 The Hot Dawg Advantage: Easy Fuel Conversion

Here’s where Modine really makes life simple. Their Hot Dawg unit heaters use a field-conversion kit to switch from natural gas to propane (or vice versa) in under an hour.

That means:

• You can buy the NG model now and convert later if you move off the grid.

• Or start with propane and switch to natural gas if a pipeline becomes available.

The kit changes the burner orifices and adjusts gas pressure to match fuel flow characteristics. No new heater required — just a licensed technician to perform the conversion (modinehvac.com ).

This flexibility is a big deal for homeowners who plan long term or might relocate. It keeps your investment future-proof.

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🧠 How to Decide: Five Smart Questions to Ask

1. Do you already have a gas line?

If yes, natural gas is almost always cheaper and easier.

2. Are you off the grid or in a rural area?

Propane gives you total control without utility dependence.

3. How often will you use the heater?

For occasional use, fuel cost differences won’t matter much. But if you run it daily all winter, natural gas saves in the long run.

4. Do you want backup power resilience?

Propane tanks keep fuel available during power outages (if your heater doesn’t depend on electric ignition).

5. Will you move or expand later?

Choosing a convertible model like the Hot Dawg lets you adapt without replacing equipment.

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🛠️ Installation and Ventilation Differences

Both fuel types use the same basic venting strategy: sealed combustion with intake and exhaust piping.

Key notes:

• Natural Gas: Uses a slightly larger diameter supply line because of lower pressure.

• Propane: Requires a regulator to step tank pressure down to the burner rating (around 11 in. WC).

The rest — mounting brackets, electrical connections, and thermostat wiring — is identical.

Because the Hot Dawg heater is ceiling-mounted and compact, your installer can keep runs short and neat to minimize heat loss (energy.gov ).

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🧮 A Quick Example: Fuel Use and Annual Cost

Imagine you run your 75,000 BTU heater for 3 hours a day over a 4-month season (≈ 360 hours total).

So propane may cost about 2.5 × as much to run over the same period. But that’s offset if you don’t have access to natural gas and use the heater only occasionally.

(values approximate; actual usage varies by climate and insulation)

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🧱 Real-World Scenario Comparisons

Urban Garage — Cleveland, OH

• Attached 2-car garage (~500 sq ft)

• Natural gas available

• Usage ≈ 2 hours/day

→ Choose Natural Gas. Lowest cost, no tank refills, minimal maintenance.

Rural Workshop — Bozeman, MT

• Detached garage (~1,000 sq ft)

• No gas main access

• Harsh winters

→ Choose Propane. Tank gives independence and a steady supply; conversion kit optional if gas line arrives later.

Seasonal Cabin — Northern Maine

• Used intermittently

• No utilities

• Power outages common

→ Propane again. Self-contained fuel source works off-grid with minimal power draw.

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🔧 Safety and Storage Considerations

Both fuels are safe when handled properly and used with modern equipment.

• Natural Gas: Light gas; rises and dissipates quickly if leaked.

• Propane: Heavier than air; settles low, so proper venting and detectors are important.

• Always install CO detectors in any enclosed space with combustion appliances.

• Follow clearance guidelines around the heater (usually 3 ft from combustibles).

Modern Hot Dawg heaters use sealed combustion chambers and direct-vent designs for safe, fume-free operation.

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🧰 Owner Tips to Maximize Fuel Efficiency

1. Insulate your garage door and ceiling. Every R-value point reduces BTU demand.

2. Use a programmable thermostat. Lower the setpoint when you’re not in the shop.

3. Maintain the burner annually. Clean flames mean clean combustion.

4. Check for leaks. Even a minor propane loss affects cost.

5. Angle louvers for even heat. You’ll feel warmer faster and run less.

These practical tweaks can trim 10–20 % off annual fuel use.

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💬 Samantha’s Take

Here’s my honest advice after helping dozens of homeowners weigh the same decision:

• If you already have natural gas service, go with it. You’ll get the lowest operating cost and never worry about tank levels.

• If you’re off the grid or live in a rural area, propane is a fantastic choice — clean, efficient, and easy to store.

• Either way, choose a convertible heater like the Modine Hot Dawg so you’re never locked in.

Think of it as buying an SUV that runs on two types of fuel — flexibility without compromise.

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🏁 Final Thoughts

At the end of the day, both natural gas and propane can deliver years of quiet, reliable garage heat if paired with a quality unit heater. The difference is mostly about infrastructure and lifestyle:

• Want plug-and-play convenience and low bills? 👉 Go natural gas.

• Need independence and off-grid capability? 👉 Go propane.

And if you’re still undecided? 👉 

Choose a heater that lets you switch any time — like the Modine Hot Dawg series. Its quick-change conversion kit means you can start on natural gas now and move to propane later (or the other way around) without replacing the whole unit.

That flexibility future-proofs your investment. So, no matter how your home’s energy setup evolves — new gas main, move to the country, or even a detached shop addition — your heater is ready to go wherever you do.

Bottom line: Focus on comfort today, keep options open for tomorrow, and let your heater work as smart as you do.

In the next blog, you will dive deep into an "Installation Walkthrough: What to Expect When Adding a Hot Dawg Heater".