Mr. Heater Big Buddy review: heating a 450 sq ft living area through a multi-day winter outage

This is a research-based review, based on manufacturer specs and published data. We do not test products. Specs come from Mr. Heater's product page for the Big Buddy (model MH18B), checked November 1, 2026. Safety guidance comes from the CDC, the Consumer Product Safety Commission (CPSC) and Ready.gov.

In a winter outage that stretches past two or three days, a one-room heater starts to feel small. Families end up living in the warm room, and the warm room needs to hold everyone. The Big Buddy is Mr. Heater's answer for that: up to 18,000 BTU an hour, rated to heat up to 450 square feet, with two swivel regulators that take a pair of 1 lb cylinders or a hose to a 20 lb tank.

There is one product change to know about. Mr. Heater says that because of import tariff changes, it has removed the fan on some MH18B units. The heat ratings on the page did not change, but check what the listing ships if the fan matters to you.

Who should buy it

• Households in cold climates without a wood stove or a generator that can run the furnace.
• Families who will gather in a living room rather than split up into bedrooms.
• Anyone who already owns a 20 lb propane tank for a grill and can buy the optional hose.
• People who will keep a battery-powered CO alarm running in the heated room.

Who should skip it

• Small rooms. In a 100 sq ft bedroom the low setting may be more than you need; the Little Buddy or Portable Buddy fit better.
• Residents of Massachusetts and Canada, where Mr. Heater restricts the sale, and homes above 7,000 feet.
• Anyone who will run it while everyone sleeps. Heat the room before bed, then turn it off and use sleeping bags.
• People who cannot store propane outdoors.

Strengths

• Three heat settings. 4,000, 9,000 and 18,000 BTU. Low stretches fuel, high recovers a cold room.
• Largest coverage in the Buddy line. Up to 450 sq ft, per Mr. Heater.
• Two fuel options. Two 1 lb cylinders for short use, or a 20 lb tank with the optional hose for days of heat.
• Indoor rating and safety systems. Mr. Heater lists indoor-safe: yes, with an oxygen depletion sensor (ODS), accidental tip-over shutoff and a heavy-duty wire guard over the burner tiles.
• No electricity needed. Piezo ignition from a single control knob.

Drawbacks

• Fuel hungry on high. 18,000 BTU an hour empties cylinders fast. The 11-hour figure is Mr. Heater's maximum with two cylinders, which implies low.
• Hose costs extra. The 20 lb hose and regulator are sold separately, and Mr. Heater says unauthorized accessories are prohibited and void the warranty.
• Fan removed on some units. Mr. Heater's own note on the product page.
• Heavy and bulky. 17.1 lb, 19 × 12 inches.
• More heat means more combustion. A bigger flame in a closed room makes ventilation and a CO alarm non-negotiable.

How it compares

The Big Buddy against Mr. Heater's smaller indoor-rated Buddy heaters. Figures are from Mr. Heater's product pages, checked November 1, 2026.

Using it in a long outage

Set up the warm room

Pick the room where everyone will spend the day, close off doorways to the rest of the house and put the heater on a hard, level floor facing open space. CPSC advises keeping space heaters at least 3 feet from anything that can burn. With a 450 sq ft rating, the Big Buddy can hold a living room, but every closed door you add makes the heat go further.

Plan the propane

Mr. Heater's smaller Little Buddy burns 3,800 BTU an hour for 5.6 hours per 1 lb cylinder, which puts a pound of propane at roughly 21,000 BTU (our arithmetic, not a Mr. Heater figure). On that basis, a 20 lb tank holds about 420,000 BTU. At 4,000 BTU on low that is roughly 100 hours of burn; at 9,000 BTU about 47 hours; at 18,000 BTU about 23 hours. Run on low 10 hours a day and one 20 lb tank covers most of a week.

1. 01Warm the room on high, then drop to low once it holds temperature.
2. 02Keep the tank outdoors where the manual allows, or follow the manual's rules for the hose run.
3. 03Turn the heater off before sleeping and use sleeping bags rated for the cold.
4. 04Check the CO alarm display each time you change settings.

Know when to leave

Ready.gov advises going to a community location with power if heat or cold is extreme. Pair the heater with a sealed alarm such as the Kidde COBD10, and see our heating without power guide for insulation and layering tactics that cut how much propane you burn.