Best Indoor-Safe Emergency Heaters (2026)

This post contains affiliate links. If you buy through them, we may earn a small commission at no extra cost to you.

When the power fails in winter and grid heat is out, indoor-safe supplemental heating becomes life-safety equipment. Traditional camp stoves and standard propane heaters are NOT safe indoors — they produce carbon monoxide that kills people every winter. Purpose-built indoor-safe propane heaters and specific alternative heat sources are the right answer. Here’s what to buy and how to use it safely.

What “indoor-safe” actually means

Indoor-safe propane heaters have specific engineered features:

• Low oxygen shutoff (LOS or ODS): automatically shuts off if oxygen levels drop below a safe threshold
• Tip-over shutoff: automatic shutoff if the heater is knocked over
• Complete combustion design: engineered to produce low levels of carbon monoxide (still produces some — ventilation still required)
• Recommended CFM ratings: most indoor-safe heaters specify a minimum room size (e.g., “for spaces 100+ square feet”) based on air exchange requirements

Even indoor-safe heaters require: cracked window for ventilation, a working CO detector in the same room, and don’t run while sleeping in most cases (check the specific model’s guidance).

The quick picks

For the best indoor-safe emergency propane heater, the Mr. Heater Buddy at 4,000-9,000 BTU is the market leader and the gold standard — LOS and tip-over shutoff, engineered for indoor use, runs on 1-lb propane bottles or connectable to larger tanks. For a bigger heat output, the Mr. Heater Big Buddy at 4,000-18,000 BTU heats larger areas. For a smaller footprint, the Mr. Heater Little Buddy is designed for small spaces and shorter runtimes.

The Buddy series — what they actually do

Mr. Heater Little Buddy (3,800 BTU)

The Mr. Heater Little Buddy is designed for small enclosed spaces — bathrooms, small bedrooms, closets. Runs on 1-lb propane bottles (5.6 hours per bottle at low setting). LOS and tip-over shutoff. Not enough heat for a whole living room but perfect for spot heating a bathroom or small bedroom during a long outage. ~$50-70.

Mr. Heater Buddy (4,000-9,000 BTU) — Best all-around

The Mr. Heater Buddy is the most popular indoor-safe propane heater in America. Two heat settings (4,000 and 9,000 BTU), heats up to 225 sq ft. LOS + tip-over shutoff. Runs on 1-lb bottles (3-6 hours) or 20-lb tank via optional hose adapter. Best for: primary emergency heat source for a living room, bedroom, or small workshop. $100-140.

Mr. Heater Big Buddy (4,000-18,000 BTU) — Best for larger spaces

The Mr. Heater Big Buddy at up to 18,000 BTU heats larger open areas — up to 450 sq ft. Similar safety features as the Buddy, but adds an optional fan for better air circulation. Runs on 1-lb bottles or 20-lb tank. Best for: heating a larger open living area or a workshop.

Non-propane indoor-safe options

Catalytic heaters

Catalytic heaters produce heat via chemical reaction rather than flame — they’re the technology inside Mr. Heater’s Buddy series but also come in dedicated units. Olympian Wave series is a well-known standalone catalytic heater brand for RVs and small spaces. Safety features similar to Buddy series.

Kerosene heaters

Modern indoor kerosene heaters are effective and inexpensive to run but produce more fumes than propane. Some models are rated for indoor use with adequate ventilation. Not our first pick due to fume production, but for large spaces where propane runtime is prohibitive, they’re an option.

Electric heaters (with battery backup)

If you have a substantial battery power station (2000Wh+), a small electric space heater becomes viable for short periods. A 750W electric heater on low will drain a 2000Wh battery in ~2 hours — useful for spot heating but not extended runtime. Better strategy: use propane for extended heating, save the battery for lights and electronics.

What to strictly avoid indoors

These options kill people every winter:

• Camp stoves — produce dangerous CO levels indoors
• Gas grills — same, plus fire risk
• Non-vented outdoor propane heaters (the “mushroom” patio heater style) — designed for outdoor use only
• Ovens or stovetops with door open — produce dangerous CO and are a fire hazard
• Generators inside the house or garage — CO from a running generator can kill within 15 minutes indoors
• Charcoal grills — extremely dangerous indoors

Ventilation and CO detection — non-negotiable

Any indoor combustion heater requires:

1. Ventilation. Cracked window minimum. The heater manufacturer’s guidance is the floor, not the ceiling.
2. Working CO detector. Battery-powered CO detector in the room where the heater is running. Test monthly. If the CO detector beeps during heater operation, TURN OFF THE HEATER, ventilate the space, and reassess.
3. Never run while sleeping in most cases. Check specific model guidance.
4. Fresh batteries in CO detector. An expired CO detector is worse than no detector because it gives false confidence.

Fuel storage considerations

• 1-lb propane bottles: shelf-stable indefinitely, easy to store, easy to swap. Have 6-12 on hand.
• 20-lb propane tank: much cheaper per unit heat, requires the adapter hose. Store outside.
• Propane doesn’t stale like gasoline — great for long-term prep
• Store propane bottles upright, in a well-ventilated area, away from heat sources

Sizing to your space

• Under 100 sq ft: Mr. Heater Little Buddy
• 100-225 sq ft: Mr. Heater Buddy
• 225-450 sq ft: Mr. Heater Big Buddy
• Larger spaces: multiple heaters or a Big Buddy plus close doors to smaller areas

For extended sub-freezing outages, focus on heating ONE room (usually a bedroom or living room), close doors to unheated areas, and layer clothing/blankets. Trying to heat the whole house with a portable heater doesn’t work.

The bottom line

For most households in winter-storm-prone areas, a Mr. Heater Buddy plus 6-12 1-lb propane bottles plus a fresh-battery CO detector is the right indoor-safe heat kit. Add a Big Buddy for larger open areas, or a Little Buddy for small-room spot heat. Never improvise with camp stoves or grills — Mr. Heater’s Buddy series exists because there’s a real market for products designed to burn safely indoors, and the price difference over unsafe alternatives is trivial compared to the risk.