Mr. Heater Buddy FLEX review: fast radiant heat for a mid-size room when the furnace is down

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 Buddy FLEX Heater (model MH11BFLEX), checked November 1, 2026. Safety guidance comes from the CDC, the Consumer Product Safety Commission (CPSC) and Ready.gov.

The Buddy FLEX is Mr. Heater's newer take on the indoor-rated propane heater. Instead of the ceramic tiles on the classic Buddy, it uses an omni-directional mesh burner that throws radiant heat across a 180° spread, up to 11,000 BTU an hour. Mr. Heater lists it as indoor-safe, excluding Canada and Massachusetts.

For a power outage, two details matter more than the burner design. It burns a 1 lb cylinder in 2 hours at full output, and it lights with an electronic igniter that runs on batteries. Both are manageable, but both need planning.

Who should buy it

• Households that want to take the chill off a mid-size room quickly, morning and evening, during a winter outage.
• People who also want a heater for ice fishing, hunting blinds or tailgates the rest of the year, which is where the accessory rail and storage compartments come in.
• Anyone who keeps spare AA or other small batteries and a battery-powered CO alarm.

Who should skip it

• Anyone planning to heat around the clock on 1 lb cylinders. At 2 to 3.5 hours each, that is 7 to 12 cylinders a day.
• Households that want a 20 lb tank setup. Mr. Heater's page lists the FLEX with a 1 lb cylinder and no hose included; the Portable Buddy and Big Buddy list 20 lb options.
• Residents of Massachusetts and Canada, and homes above 7,000 feet.
• Anyone who wants a heater with no batteries at all. The Little Buddy uses a Piezo igniter.

Strengths

• More output than the Portable Buddy. Up to 11,000 BTU and 275 sq ft versus 9,000 BTU and 225 sq ft.
• Wide radiant spread. Mr. Heater describes a full 180° spread from the mesh burner, so more of the room feels the heat.
• Three shutoff systems. A low-oxygen safety system, a 50° tip-switch and a thermal shut-down system, per Mr. Heater.
• Indoor rating from the maker. Listed as indoor-safe, excluding Canada and Massachusetts.
• Built-in storage. Side compartments for the ignition batteries, gloves or documents.

Drawbacks

• Shortest cylinder life in the line. 2 hours at max and 3.5 at min, per Mr. Heater, against 6 hours on low for the Portable Buddy.
• Battery-dependent ignition. Dead ignition batteries in a cold house is a problem you can avoid only by stocking spares. Mr. Heater's page does not list the battery type; check the manual.
• No hose in the box. Mr. Heater lists hose and regulator as not included and says unauthorized accessories are prohibited.
• Fuel adds up. 0.121 gallons an hour is the burn rate Mr. Heater lists.

How it compares

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

Using it in a long outage

Use it in sessions

The FLEX is at its best when it runs hard for an hour to bring a closed room up to temperature, then shuts off while blankets, layers and a closed door hold the heat. Running it continuously on 1 lb cylinders turns a week-long outage into a pile of 50 or more cylinders. Plan two or three sessions a day: morning, late afternoon and before bed.

Fuel and batteries

1. 01Count cylinders at about two per session at max, or one per session at min.
2. 02Store cylinders outdoors or in a detached shed and change them outside with the heater off.
3. 03Keep a spare set of ignition batteries taped inside the heater's storage compartment.
4. 04Keep the heater at least 3 feet from anything that can burn, the clearance CPSC advises for space heaters.

Mr. Heater's burn rate of 0.121 gallons an hour at max works out to roughly 0.5 lb of propane an hour (our arithmetic, at about 4.2 lb per gallon), which matches its 2-hour runtime per 1 lb cylinder.

Sleeping and the limits of portable heat

Turn the heater off before sleeping unless an adult is awake and the CO alarm is running. Ready.gov advises going to a community location with power if heat or cold is extreme. For a longer outage plan, see our winter power outage survival guide, and pair the heater with a sealed alarm such as the First Alert CO710.