Mr. Heater Big Maxx MHU50 Natural Gas Unit Heater Review

There's a point where electric garage heat stops making sense, and it arrives quickly in a big or uninsulated space. A three-car garage with a 10-foot ceiling and no insulation can need 40,000–50,000 BTU to hold a working temperature on a cold day — two and a half to three 5,000W electric units, on two or three dedicated 30A circuits, at electric rates. The Big Maxx makes that heat from one gas appliance, and in most of the country natural gas costs roughly a third as much per BTU as resistance electric. If you heat the shop often, the installation cost pays itself back.

It's a real unit heater: forced-air, power-vented, electronic ignition, controlled by an ordinary 24V wall thermostat so you can set 50°F overnight and 65°F when you're working. It hangs from the ceiling on included brackets (minimum 8 feet to the floor) and the exhaust runs through a wall or the roof with a vent kit. Mr. Heater includes the propane conversion kit, so it works in rural shops on a tank too.

Be honest about the install. It's a gas line, a vent through the building envelope, a 115V outlet, a thermostat run, and a permit in most places; unless you're a licensed gas fitter, that's a pro job, and a few hundred dollars of parts beyond the unit itself. Put a CO alarm in the garage and another in any adjacent living space, follow the clearances exactly, and never block the intake or vent. Done right, it's the best heat per dollar in this guide by a wide margin.