Is Propane Right for You? Comparing Propane vs. Natural Gas Heater Efficiency and Sizing Rules

When the winter cold hits and your garage feels like a meat locker, the last thing you want is to second-guess your heater. But if you’re building a new workspace, upgrading your unit, or trying to cut heating costs, the big question always comes up:

Should I go with propane or natural gas?

I’ve installed hundreds of heaters over the years—some in suburban workshops, others in detached garages miles from a gas line—and I can tell you there’s no single “right” answer.

👉 Explore the Reznor UDX 60,000 BTU Propane Unit Heater for a perfect mid-size garage setup

The better question is: Which one fits your setup, climate, and budget best?

This guide will walk you through exactly how propane and natural gas stack up in efficiency, cost, safety, sizing, and real-world performance. By the time you’re done, you’ll know whether you should stick with the pipeline—or go with the tank.

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🧱 1. Propane vs. Natural Gas — What’s the Real Difference?

On paper, propane and natural gas look pretty similar. They’re both clean-burning fuels used to power furnaces, garage heaters, and water heaters. But how they arrive at your heater—and how much heat they produce—are two very different stories.

🔹 Natural Gas: Utility Pipeline Power

Natural gas comes straight from your local utility through an underground pipeline. It’s mostly methane, which is lighter than air and easy to distribute citywide.

For most homeowners, this means:

• No fuel deliveries.

• Consistent pressure and supply.

• Lower per-unit cost.

But you need a connected line, which often means permits, trenching, and hookups if your garage isn’t already tied in.

🔹 Propane: The Off-Grid Fuel

Propane is stored as a liquid under pressure in a tank, then vaporized and piped into your heater. It’s perfect for:

• Detached garages

• Barns, workshops, or off-grid properties

• Rural homes without gas service

Unlike natural gas, propane is energy-dense—it packs roughly 2.5 times more BTUs per cubic foot.

According to the U.S. Energy Information Administration:

• 1 cubic foot of propane = 2,516 BTUs

• 1 cubic foot of natural gas = 1,030 BTUs

That means a gallon of propane delivers more heat, faster, but also costs a bit more per unit.

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⚙️ 2. Efficiency and BTU Output — Understanding the Numbers

Every heater is rated by its BTU (British Thermal Unit) output—the amount of heat it can produce per hour.

But the fuel efficiency behind that number changes depending on what’s flowing through the lines.

In other words:

• Propane burns hotter and cleaner, giving you more heat per unit of volume.

• Natural gas costs less per therm, but you need more of it to get the same result.

Tony’s Take:

“Think of propane as premium fuel. You’ll pay a bit more per gallon, but it runs cleaner, burns hotter, and gets the job done faster—especially in colder garages.”

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🧮 3. How to Size Your Heater by Fuel Type

Whether you’re using propane or natural gas, your BTU requirement starts with the same math:

BTUs = (Square Footage × 50) × Climate Factor

Then, adjust for your fuel efficiency.

Source: U.S. Department of Energy Climate Zone Map

Example — 24x24x9 Garage in Ohio

Square footage: 576 sq. ft.
Climate factor: 1.25
BTU need: 576 × 50 × 1.25 = 36,000 BTUs base load

Add for uninsulated surfaces or ceiling height (roughly ×2 for garages), and you’re looking at 60,000–70,000 BTUs.

Propane recommendation: 60k heater
Natural gas recommendation: 70k heater

Why the difference? Because propane burns hotter and produces more BTUs per cubic foot—so it reaches target temperature faster.

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💰 4. Fuel Cost Comparison (2025 Averages)

Let’s break down the real numbers—because fuel prices matter just as much as efficiency.

So, yes—natural gas costs less per BTU on average. But propane often wins in rural areas because of one thing: no utility fees.

With natural gas, you might pay monthly base charges or service fees even when you’re not heating. Propane? You pay only for what you burn.

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🏗️ 5. Installation and Maintenance Costs

🔹 Propane Setup

• Tank installation: $300–$600 (above-ground)

• Regulator + line: $100–$200

• No utility trenching required

• Can be DIY-friendly with pro inspection

🔹 Natural Gas Setup

• Utility hookup: $500–$1,200

• Trenching or new line installation: $10–$25/ft

• Must be installed by a licensed plumber or HVAC tech

• Typically longer permit process

Tony’s rule:

“If you already have a natural gas line in your home, it’s usually cheaper to tie in. But if you’re starting from scratch or heating a detached space, propane’s plug-and-play advantage can’t be beat.”

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🔥 6. Which One Heats Faster?

Propane wins here, hands down.

Because it contains more BTUs per cubic foot, propane reaches your target temperature faster and recovers heat loss quicker after you open the garage door.

This makes propane the go-to for:

• Workshops where doors open frequently

• Cold climates where fast recovery matters

• Large or detached garages that cool off quickly

Natural gas systems perform best in steady-use, attached setups where heat loss is minimal.

Tony’s story:

“I’ve seen propane heaters warm a 700 sq. ft. shop from 30°F to 65°F in 15 minutes flat. A comparable natural gas system might take twice as long—but cost less per hour once it’s running.”

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🧯 7. Safety and Storage Considerations

Safety should always come before fuel type. Both propane and natural gas are safe when properly installed—but they behave differently in leaks.

🔹 Propane Safety

• Tanks should be at least 10 ft from ignition sources.

• Never store indoors or below grade.

• Always use a certified regulator and leak test fittings with soapy water.

🔹 Natural Gas Safety

• Ensure adequate ventilation—especially with non-sealed units.

• Install carbon monoxide detectors in any enclosed space.

• Check for corrosion or cracks in flex lines yearly.

For full safety guidance, see the U.S. Consumer Product Safety Commission’s CO Safety Page.

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⚡ 8. Energy Efficiency and Environmental Impact

Here’s the part most people skip—but it matters.

🔹 Emissions

Propane: 12% less CO₂ per BTU than natural gas
Natural gas: Lower total CO₂ emissions when pipeline-delivered

Both fuels are considered low-emission, clean-burning options under the EPA Energy and Environment Program.

🔹 Efficiency Ratings

• Propane heaters: typically 90–95% AFUE

• Natural gas heaters: typically 85–90% AFUE

Over a 10-year lifespan, that 5% difference adds up—especially in cold states where the heater runs hundreds of hours a year.

Tony’s rule of thumb:

“In warmer climates, efficiency doesn’t matter much. In Michigan or North Dakota? Every percent counts.”

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🧰 9. Converting Between Propane and Natural Gas

If you already have one fuel type but want to switch, most modern heaters can be converted.

Example: The Reznor UDX 60,000 BTU Propane Unit Heater comes with optional conversion kits.

But note:

• Propane systems run at higher pressure (~10" WC vs. ~3.5" WC).

• Conversion requires new orifices, regulators, and burner tuning.

• Always use a licensed technician — never attempt it DIY.

“I’ve seen too many good heaters ruined because someone tried to ‘just swap the line.’ Propane and gas may look the same, but they burn very differently.”

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💡 10. Long-Term Cost of Ownership

Let’s do some real math.

Assume a 60,000 BTU garage heater running 4 hours/day for 90 days per winter (216 hours total):

So natural gas costs less overall—but propane users save in installation and flexibility.

Add in propane’s faster warm-up and rural availability, and it often balances out.

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🏠 11. When Propane Is the Better Choice

If any of these apply, propane’s likely your winner:

✅ Detached or rural garage (no gas line nearby)
✅ Frequent door openings (needs faster recovery)
✅ Cold climate (denser heat output)
✅ You want to control your own fuel (no monthly utility bills)

Tony’s field note:

“If you’re more than 100 feet from a gas main or paying for trenching, propane will almost always come out cheaper over the next five years.”

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🏙️ 12. When Natural Gas Makes More Sense

Natural gas fits best when:

✅ You already have utility service
✅ Your garage is attached to the home
✅ You want lower per-BTU operating costs
✅ You don’t want to refill tanks or check regulators

For steady heat and long-term use, it’s hard to beat.

“If the line’s already there, I’d hook up to it and never think twice. But if I’m working in a detached pole barn, propane’s the king.”

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🧱 13. Propane vs. Natural Gas: Efficiency at a Glance

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🧠 14. Tony’s Quick Field Formula for Fuel Choice

Here’s the simple way I help homeowners decide:

If your gas line is already in place → go natural gas.

If you’d have to trench or pull new utility service → go propane.

If you’re in a cold region or need fast recovery → go propane.

If you heat steadily all winter long → natural gas wins on cost.

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⚙️ 15. The Best Garage Heater Models by Fuel Type

Each one meets Energy Star efficiency standards and can be sized for your specific climate zone.

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🧭 16. Final Thoughts — Tony’s Take

When homeowners ask me, “Is propane really worth it?” I tell them this:

“Both fuels do the job. The trick isn’t picking the ‘better’ one—it’s picking the one that fits your setup.”

If you’re in a suburban neighborhood with gas service, natural gas is a solid, cost-efficient choice that’ll run smoothly for decades.

If you’re in the country or heating a detached building, propane is unbeatable for flexibility and fast, reliable warmth.

No matter which you choose:

• Size your heater correctly.

• Seal and insulate your garage.

• Keep your system maintained yearly.

That’s the formula for warm hands, happy tools, and a lower heating bill—no matter what’s in your tank.