Best Gas Unit Heater for Garage: Reliable Garage and Shop Heating Solutions

Choosing the right gas unit heater for a garage depends on garage size, fuel type, venting, and installation options. The table below summarizes five top-rated heaters selected for coverage range, BTU output, and mounting flexibility so you can compare at a glance.

Product	BTU	Fuel	Coverage/Notes
Mr. Heater Big Maxx MHU80NG	80,000 BTU	Natural Gas	Up To 2,000 Sq. Ft., Ceiling/Wall Vent Options
Mr. Heater MHU80LP	80,000 BTU	Propane	Heats Up To ~1,000 Sq. Ft., Ceiling Mount
Reznor UDXC-45	45,000 BTU (multi-stage)	Natural Gas	Two Output Levels, 83% Efficiency, Ceiling Mount
Reznor UDXC-60	60,000 BTU (multi-stage)	Propane	Two Output Levels, 83% Efficiency, Ceiling Mount
Modine HD45AS0111 Hot Dawg	45,000 BTU	Natural Gas	Quiet Operation, 80%+ Efficiency, Ceiling Mount Option

Mr. Heater Big Maxx MHU80NG Natural Gas Unit Heater

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This Mr. Heater Big Maxx model delivers 80,000 BTU with coverage suitable for larger garages or workshops, rated to cover up to 2,000 sq. ft. The unit is supplied with two angle brackets and includes an LP conversion kit, although thermostat, hose, and regulator are not included. Its physical dimensions are 29.33” L x 15.50” W x 26.37” H and it operates on 120 V drawing about 2.3 amps. The heater requires a minimum 8 ft. clearance from the floor to the base of the unit and supports Category 1 vertical and Category 3 horizontal venting configurations. This model is intended for use with natural gas but provides conversion capability for LP when needed.

Mr. Heater Propane Unit Heater MHU80LP 80,000 BTU

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The MHU80LP is the propane-fueled counterpart offering 80,000 BTU, designed to heat up to approximately 1,000 square feet depending on insulation and climate. It includes two angle brackets for ceiling mounting and features a spark ignition with a self-diagnostic control module for safer start-up and troubleshooting. This model is targeted for ceiling-mounted installations in shops and garages where propane supply is preferred or where natural gas is not available.

Reznor UDXC-45 Natural Gas 45,000 BTU Unit Heater

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The Reznor UDXC-45 is a mid-size natural gas heater rated at 45,000 BTU with two output levels: low-fire ~26,145 BTU and high-fire ~37,350 BTU, providing flexibility for variable winter conditions. It achieves an 83% thermal efficiency rating, suitable for garages, workshops, and small warehouses. The unit is designed for indoor use with threaded-nut retainers at four suspension points for ceiling mounting; mounting brackets are sold separately. The forced air, low-static propeller fan aims to deliver quiet operation compared with some high-velocity industrial heaters.

Reznor UDXC-60 Propane 60,000 BTU Garage Heater

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The Reznor UDXC-60 is a 60,000 BTU propane-fired unit with two output stages: low-fire ~34,860 BTU and high-fire ~49,800 BTU, also rated at 83% efficiency. It’s intended for indoor use in garages and workshop spaces where propane is the preferred fuel. The UDXC-60 provides ceiling-mount capability via suspension points and is aimed at providing even heat distribution with a low static propeller fan. Mounting hardware is typically sold separately, allowing flexibility in placement based on shop layout and ducting needs.

Modine Hot Dawg HD45AS0111 Natural Gas 45,000 BTU Heater

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The Modine Hot Dawg HD45AS0111 provides 45,000 BTU and is certified for residential, commercial, and industrial applications. It features a low-profile grey cabinet designed for quieter operation and space-saving installation. The Hot Dawg series emphasizes reliable performance with an efficient heat exchanger and is commonly used in garages and shops where a certified unit heater is needed. Its neutral design integrates with typical garage interiors while offering ceiling or wall-mount options depending on installation requirements.

Buying Guide: How To Choose A Gas Unit Heater For Your Garage

Selecting the right gas unit heater requires evaluating several technical and practical factors. Below are key considerations to compare units and match a heater to your garage’s needs.

1. Fuel Type: Natural Gas Vs. Propane

• Natural Gas: Typically cheaper if piped to your property; common in urban/suburban areas. Some models offer conversion kits for propane.
• Propane: Portable and useful where natural gas service is not available; requires tank storage and periodic refilling.

2. BTU Output And Coverage

BTU indicates heating capacity; higher BTU values suit larger or less-insulated spaces. Estimate required BTU by garage volume, insulation quality, and desired indoor temperature. As a rule of thumb, confirm manufacturer coverage estimates (sq. ft.) and consider a buffer if insulation is poor.

3. Efficiency Ratings

Higher thermal efficiency means more heat is delivered for the same fuel input. Look for efficiency percentages or AFUE ratings; models like the Reznor UDXC series list an ~83% thermal efficiency which reduces fuel consumption compared to lower-efficiency units.

4. Venting And Clearance Requirements

• Check venting category (e.g., Category 1 vertical/Category 3 horizontal) and ensure compatibility with your building for safe exhaust routing.
• Observe minimum clearances from floor, walls, and combustibles. For example, some units specify minimum height or clearance in installation specs.

5. Mounting Options And Installation

Decide between ceiling-mount, wall-mount, or floor-mounted heaters. Ceiling-mount saves floor space and often distributes heat more evenly. Verify included hardware: some models include mounting brackets while others require separate purchase. Consider hiring qualified HVAC or gas-pro appliance installers when venting or gas line work is needed.

6. Ignition And Controls

• Spark ignition and self-diagnostic modules add safety and ease of use for start-up and troubleshooting.
• Thermostat compatibility: check if a thermostat is included or must be purchased separately for automated temperature control.

7. Noise And Airflow

Low-static propeller fans or quiet forced-air designs reduce operational noise for garage work environments. Consider fan type if noise is a concern and ensure airflow patterns suit your workspace layout.

8. Safety Features

• Sealed combustion or direct vent systems limit indoor combustion air use and improve safety in attached garages.
• Look for safety pilots, pressure regulators, and automatic shut-off features where applicable.

9. Maintenance And Serviceability

Regular maintenance includes checking burners, vents, and ignition components. Prefer models with accessible panels and a network of replacement parts or authorized service centers.

10. Regulatory And Certification Considerations

Confirm the heater is certified for indoor use (residential/commercial) in your jurisdiction and meets local building and fuel codes. Some heaters are specifically certified for residential or industrial environments; choose accordingly.

Comparison Perspectives

• Large Garage / Workshop: High-BTU units like 80,000 BTU models provide rapid heat for larger volumes and poorly insulated spaces. Consider Mr. Heater 80,000 models when fuel supply and venting allow.
• Medium Garage / Attached Garage: 45,000–60,000 BTU units (Reznor UDXC series, Modine Hot Dawg 45k) balance efficiency, quieter operation, and lower installation requirements.
• Fuel Availability: Choose natural gas units where piping exists; select propane models where portability or tank supply is necessary.
• Installation Complexity: Units requiring special venting or external power may need professional installation; factor this into project planning and timelines.