Choosing a powerful gas heater is essential for efficiently warming large commercial or industrial spaces.
A 400k BTU gas heater offers high heat output, fast temperature recovery, and reliable performance even in demanding conditions. However, power alone is not enough.
Warranty coverage plays a crucial role in protecting your investment, ensuring long term reliability, and reducing maintenance costs.
The best models combine durability, safety features, energy efficiency, and strong manufacturer support.
In this guide, we highlight the top 10 best 400k BTU gas heaters that deliver exceptional heating performance while offering dependable warranty coverage for peace of mind and value.
10. Dura Heat EWH5510 Electric Heater
The Dura Heat EWH5510 is a high‑output electric forced‑air heater built for garages, workshops, and agricultural spaces that need fast, reliable warmth.
With a 17,060 BTU output (5,000 W at 240 V, 30 A), it comfortably heats up to 600 sq ft, delivering consistent temperature even in poorly insulated areas.
The unit is hard‑wired for safety and must be installed by a professional; once connected, a power‑indicator light confirms the heater is ready to run.
Control is effortless thanks to the included remote with an LED display that lets you set the thermostat from 45 °F to 99 °F and program a 12‑hour timer.
Adjustable louvers let you direct airflow for focused or wide‑area heating, while the built‑in overheat protection sensor automatically shuts the unit down if temperatures rise too high.
Its rugged steel cabinet, insulated scratch‑resistant housing, and spiral‑wrapped heating coil guarantee durability in tough environments.
A versatile wall or ceiling mounting bracket frees up floor space, making this heater a practical, space‑saving solution for any workshop or garage.
Pros
- Heats up to 600 sq ft efficiently
- Remote control with thermostat and timer
- Overheat protection shuts off automatically
- Durable steel body resists scratches
- Adjustable louvers direct airflow precisely
Cons
- Requires professional hard‑wired installation
- No plug‑in option available
- Remote batteries not included
9. Mr. Heater 125k BTU Forced Air Propane Heater
The Mr. Heater 125,000 BTU Forced‑Air Propane Space Heater (model MHC125FAV) delivers powerful, portable heat for large indoor workspaces. Thanks to Quiet Burner Technology, the unit runs with minimal noise—ideal for focused tasks in construction sites, barns, warehouses, or workshops.
With a heating capacity of up to 3,125 sq ft., it quickly raises temperatures in expansive areas. The package includes a 10‑ft. hose and regulator, allowing flexible placement and easy connection to a propane source.
Designed for well‑ventilated environments, this forced‑air heater circulates warm air efficiently, providing consistent comfort without the bulk of permanent heating systems. Its rugged construction stands up to the rigors of job‑site use, while the intuitive controls make operation straightforward for anyone on the crew.
Pros
- Quiet Burner for low‑noise operation
- Heats up to 3,125 sq ft. quickly
- Portable with 10‑ft. hose included
- Simple regulator attachment system
- Durable build for tough environments
Cons
- Requires adequate ventilation
- Not suited for outdoor use
- Propane tank needed separately
8. Mr. Heater 140,000 BTU Forced Air Kerosene
The Mr. Heater MH140CKT delivers powerful, reliable warmth for large spaces, heating up to 3,500 sq ft with its 140,000 BTU forced‑air output.
Its easy‑fill 8‑gallon kerosene tank provides up to 8 hours of continuous operation, while the multi‑fuel capability lets you switch between kerosene, diesel or gasoline when needed.
A built‑in thermostat automatically maintains your desired temperature, and the flat‑free design eliminates the hassle of tire maintenance. Engineered for sub‑zero reliability, this unit is perfect for workshops, garages, cabins, or emergency backup heating.
The robust construction and straightforward controls make it a dependable choice for anyone needing fast, portable heat without the complexity of permanent installations.
Pros
- Heats up to 3,500 sq ft quickly
- Up to 8 hours of runtime
- Easy‑fill 8‑gallon tank
- Thermostatically controlled temperature
- Flat‑free, no tire maintenance
Cons
- Requires ventilation for safe use
- Heavy to move when full
- Fuel cost varies by type
7. Dura Heat DFA80T Kero Forced Air Heater
The Dura‑Heat DFA80T delivers 80,000 BTU of forced‑air heat, easily covering up to 2,000 sq ft—perfect for large workshops, construction sites, or outdoor events.
Its multi‑fuel capability lets you run on K‑1 kerosene, #1 & #2 fuel oil, diesel, JP‑8, or jet fuel, giving you flexibility wherever the job takes you.
A high‑performance motor drives a large‑area fan for rapid, uniform warming, while the one‑touch electronic ignition and LED temperature readout make start‑up and monitoring effortless.
Choose between electric or kerosene operation to match power availability, and rely on built‑in safety features such as flame‑out shut‑off, overheat protection, and a drain plug for peace of mind.
A full 5‑gallon tank provides up to 8.5 hours of continuous heat, and the rugged, contractor‑grade construction—including a handy carrying handle—means the unit stands up to tough indoor and outdoor environments. CSA certification and a 1‑year warranty round out a dependable heating solution built for professionals.
Pros
- Heats up to 2,000 sq ft quickly
- Multi‑fuel flexibility for any site
- Long 8.5‑hour run time per tank
- Built‑in safety shut‑off system
- LED diagnostics simplify troubleshooting
Cons
- Heavy for frequent relocation
- Requires 5‑gallon fuel tank refill
- Electric option needs reliable power source
6. Mr. Heater F260560 Big Maxx NG Unit Heater
The Mr. Heater F260560 Big Maxx MHU80NG is a powerful, ceiling‑mounted natural‑gas unit heater designed for garages, barns, workshops, and other large workspaces.
Delivering 80,000 BTU, it can comfortably warm up to 2,667 sq ft—roughly the size of a three‑ or four‑car garage. Its low‑profile construction fits under a minimum 10‑ft ceiling with just 8 ft of clearance from the base to the floor, keeping the space clear for equipment and vehicles.
The unit is compatible with standard 24‑volt thermostats or newer Wi‑Fi‑enabled thermostats (sold separately) for precise temperature control.
Safety is built in with a high‑temperature shut‑off switch and a gas‑safety flame sensor, ensuring the heater turns off automatically if unsafe conditions arise.
Installation is straightforward for those familiar with forced‑air systems, and the robust forced‑air design quickly distributes warm air throughout the area, turning a cold workshop into a comfortable, productive environment.
Pros
- Heats up to 2,667 sq ft efficiently
- Low‑profile fits tight ceiling spaces
- Compatible with Wi‑Fi thermostats
- High‑temp safety shut‑off included
- Powerful 80,000 BTU output
Cons
- Requires 24‑volt thermostat (extra)
- Needs professional gas line installation
- Ceiling mounting may need structural support
5. Dura Heat DFA220CV Kero Forced Air Heater
The Dura Heat DFA220CV delivers reliable warmth for workshops, cabins, or construction sites, combining a robust 180K‑220K BTU output with dual heat‑control settings for precise temperature management.
Its 13‑gallon kerosene tank provides up to 10 hours of continuous heat on a single fill, minimizing refuel interruptions.
A built‑in air pressure gauge lets you monitor fuel flow at a glance, while the integral auxiliary power outlet supplies 120 V for tools or lights, turning the heater into a versatile power hub.
With a generous airflow of 650 CFM, the unit distributes heat quickly and evenly across the space. The sleek white/black housing not only looks professional but also resists corrosion, making it ideal for demanding indoor or semi‑outdoor environments.
Pros
- Up to 10 hours runtime per tank
- Built‑in auxiliary 120 V power outlet
- Real‑time air pressure gauge monitoring
- High 650 CFM airflow capacity
- Large 13‑gallon fuel tank
Cons
- Requires regular tank refilling
- Noise level noticeable in quiet rooms
- No built‑in thermostat control
4. Dynaglo 210,000 BTU Forced Air Kerosene Heater
The 210,000‑BTU forced‑air kerosene heater delivers powerful, whole‑room warmth for spaces up to 5,250 sq ft, making it ideal for workshops, garages, and large outdoor shelters.
A 14‑gallon fuel tank provides roughly eight continuous hours of heat, while the adjustable thermostat lets you fine‑tune the temperature for comfort and efficiency.
A high‑output fan circulates warm air quickly, eliminating cold spots, and built‑in no‑flame and over‑heat sensors automatically shut the unit off for added peace of mind.
Convenient features include a bright power‑indicator light, built‑in cord storage to keep the work area tidy, and oversized rubber tires that glide over concrete or gravel with minimal effort.
The compact footprint—approximately 18 × 40‑1/5 × 22 inches—fits into tight corners, and the heater comes backed by a one‑year limited warranty, ensuring reliable performance season after season.
Pros
- Heats up to 5,250 sq ft effortlessly
- 8‑hour runtime on a single tank
- Adjustable thermostat for precise control
- Auto shut‑off safety sensors included
- Oversized tires enable easy mobility
Cons
- Requires kerosene fuel supply
- Heavy for one‑person lifting
- No built‑in thermostat backup battery
3. Reddy Heater 60,000 BTU Propane Heater
The Reddy Heater 60,000 BTU Forced‑Air Propane Heater is built for tough, high‑output heating where you need it most.
With a robust steel housing and a brass burner nozzle, this unit delivers a powerful 30,000‑60,000 BTU range that can comfortably warm spaces up to 1,500 sq ft—perfect for garages, workshops, job sites, and construction zones.
Its low‑pressure propane system is engineered for durability, featuring fewer moving parts than high‑pressure alternatives, which translates to reduced wear and longer service life.
One‑touch electronic ignition gets you heat on in seconds, while the adjustable base stand lets you position the heater for optimal airflow. Certified by CSA for rain, wind, and both indoor and outdoor use, the Reddy Heater meets stringent safety standards, giving you peace of mind in any environment.
Pros
- High BTU output covers large areas
- Low‑pressure system reduces maintenance
- One‑touch ignition for instant heat
- Adjustable stand for flexible placement
- CSA certified for outdoor safety
Cons
- Requires propane tank hookup
- No built‑in thermostat control
- Heavy steel construction limits portability
2. Mr. Heater 60,000 BTU Forced Air Propane Space Heater
The Mr. Heater MHC60FAV delivers powerful, adjustable warmth for demanding work environments.
With a variable output ranging from 30,000 BTU up to a robust 60,000 BTU, this forced‑air propane heater can quickly raise temperatures in large, well‑ventilated spaces such as construction sites, barns, warehouses, and workshops.
A 10‑foot hose and regulator are included, giving you flexible placement and easy connection to a propane tank. The oversized, glove‑friendly handle makes transport and positioning effortless, while the adjustable heating angle lets you direct airflow exactly where it’s needed.
Designed for durability, the unit’s rugged housing tolerates the rigors of job‑site use, and the simple controls let anyone operate it safely and efficiently.
Pros
- Variable heat output up to 60,000 BTU
- Includes 10‑ft hose and regulator
- Glove‑friendly handle for easy carrying
- Adjustable airflow direction
- Built for tough, ventilated environments
Cons
- Requires proper ventilation
- Not suited for enclosed spaces
- Propane tank needed separately
1. Dyna Glo KFA400DGD Kerosene Heater
The Dyna Glo KFA400DGD is a powerhouse kerosene forced‑air heater designed for large spaces. With a massive 400,000 BTU output, it can comfortably warm up to 8,500 sq ft, making it ideal for workshops, barns, or emergency heating in commercial settings.
The built‑in thermostat and digital display let you set and monitor the temperature with precision, while the flame‑out sensor automatically shuts the unit down for added safety.
Its dual‑source power cord offers flexibility for both 120 V and 240 V connections, and the front‑and‑rear lift handles plus cord wrap make transport and storage effortless. Constructed from rugged, heavy‑duty materials, this heater stands up to harsh environments and frequent use.
Key Features
– 400,000 BTU heating capacity
– Coverage up to 8,500 sq ft
– Comfort‑control thermostat with digital display
– Dual‑source power cord (120 V / 240 V)
– Front and rear lift handles, cord wrap
– Flame‑out safety sensor
– Sturdy, rugged construction
Pros
- Massive 400,000 BTU output
- Heats large spaces quickly
- Precise thermostat control
- Flexible dual‑voltage power options
- Durable, rugged build
Cons
- Heavy and bulky to move
- Requires proper ventilation
- Higher fuel consumption at full power
Frequently Asked Questions
What should I look for when choosing a 400k BTU heater with warranty coverage?
- Warranty length and terms – Aim for at least a 2‑year parts and labor warranty; check if it covers the heat exchanger, igniter, and control board.
- Fuel type & efficiency – Natural gas, propane, or dual‑fuel models are common; higher AFUE (≥85 %) means lower operating costs.
- Safety features – Look for flame‑failure protection, overheat shut‑off, and a sealed combustion system.
- Installation requirements – Verify clearance distances, venting needs, and whether a professional installer is required to keep the warranty valid.
How does warranty coverage differ between major brands for 400k BTU heaters?
- Brand A typically offers a 5‑year limited warranty on the heat exchanger and a 2‑year warranty on all other components, provided the unit is installed by a certified technician.
- Brand B provides a 3‑year full‑coverage warranty (parts + labor) with an optional extended plan that can be purchased at the time of sale.
- Brand C includes a 2‑year warranty on the entire unit but offers a lifetime warranty on the stainless‑steel heat exchanger if regular maintenance logs are submitted.
Always read the fine print: some warranties become void if the heater is used with the wrong fuel type or if routine service is missed.
Can I maintain the warranty on a 400k BTU heater while performing DIY maintenance?
Yes, most manufacturers allow owners to perform basic upkeep (cleaning the burners, replacing air filters, checking venting) without voiding the warranty, as long as:
1. The work follows the manufacturer’s service manual.
2. All modifications or repairs are performed by a licensed HVAC technician when required (e.g., heat exchanger inspection, gas line work).
3. You keep a detailed service log and retain receipts for any parts or professional services.
Conclusion
Choosing the right 400k BTU heater ultimately comes down to balancing heating power, energy efficiency, and the peace of mind that a solid warranty provides.
A reliable unit should deliver consistent warmth across large spaces while offering smart controls and safety features that protect both your home and your wallet.
Look for manufacturers that stand behind their products with comprehensive coverage, easy claim processes, and responsive customer support.
By prioritizing these factors, you can invest in a heating solution that not only meets demanding performance needs but also safeguards your long‑term satisfaction, ensuring comfort throughout the colder months.
