Staying Warm in a Winter Power Outage

Why does the heat stop in a winter power outage?

The heat stops because almost every modern gas furnace and boiler depends on electricity to run its controls, light its burner and move heat through the house. Carrier's 59SC5A installation manual says the furnace "must have a 115-v power supply", and Lennox's EL297 manual describes an automatic hot surface ignition system and warns, "Do not attempt to manually light burners on this furnace."

So a full gas line does not mean heat. The inducer fan, the igniter, the blower for a forced-air system and the circulator pumps for a boiler all stop with the power. A heat pump stops too. Gas fireplaces and wood stoves that need no power can keep a room warm, but they are vented appliances, and a blocked flue still pushes carbon monoxide indoors.

Valley nights are long and cold: NOAA's 1991–2020 normals put the January average low at the Aspen 1SW station at 9.9°F. No source gives a reliable figure for how long a house stays warm without heat, so plan for pipes as well as people; the frozen pipes page covers what to do with the water.

Outage numbers that matter

• 20 ftMinimum generator distance from windows, doors and ventsCDC
• 3 ftClear space around a space heaterU.S. Fire Administration
• 9.9°FJanuary average low, Aspen 1SW (1991–2020)NOAA NCEI

How do you stay warm safely in a power outage?

Stay warm by gathering everyone into one room, dressing in loose layers, and using only heat sources that are safe indoors. Ready.gov's power outage page adds: have a flashlight for every household member, plan ahead for medical devices that need power, and "go to a community location with power if heat or cold is extreme."

Before winter, check that your carbon monoxide alarms have battery backup. Ready.gov says to put CO detectors with battery backup in central locations on every level, and CPSC says the same about every level and outside sleeping areas; that is advice. Colorado's 2009 law requires an alarm no more than 15 feet from the doorway of every room used for sleeping, in the situations it lists, such as a home sale or permitted furnace replacement. More detail is on the carbon monoxide safety page.

If you smell gas at any point, leave first. Then, from outside and well away, call 911 and Black Hills Energy; do not flip light switches or use phones inside.

Where can a generator run safely?

A portable generator runs safely only outdoors, at least 20 feet from windows, doors and vents, with its exhaust pointed away from the house. The CDC says never to use a generator inside a home or garage "even if doors and windows are open", and CPSC adds basements, crawlspaces and sheds to that list.

In deep snow, that means clearing a spot well away from the house rather than tucking the generator under a deck or into an open garage. CPSC's May 2026 release recommends generators with a carbon monoxide shut-off feature and says models certified to PGMA G300-2023 and UL 2201-2023 include CO safety technology.

Running a furnace from a generator is a separate job. Carrier says the furnace's electronics need power with "a smooth sinusoidal waveform" and that other power "may damage the furnace electronics or cause erratic operation." Ask a licensed electrician how to connect a generator to the house, and ask your heating technician whether your model will run on it.

Are space heaters safe in a power outage?

An electric space heater is only useful in an outage if you have safe generator power for it, and it is only safe with space around it. The U.S. Fire Administration says to keep anything that can burn at least 3 feet from all heat sources, including space heaters, fireplaces and wood stoves, and to turn space heaters off when you leave the room or go to sleep.

Fuel-burning heaters bring the carbon monoxide risk indoors. Use only heaters made for indoor use, follow their manuals, and keep CO alarms working nearby. The USFA also says to have heating equipment and chimneys cleaned and inspected every year by a professional.

What should you never use for heat?

Never heat a home with a gas oven or stovetop, a charcoal grill, a camp stove or a generator. Ready.gov says a gas stove or oven used for heat "increases your risk of carbon monoxide poisoning", and the CDC's carbon monoxide page says plainly, "Never heat your house with a gas oven."

Carbon monoxide has no smell or color. The CDC lists headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion as the common symptoms, and warns that people who are asleep can die before they notice anything. If an alarm sounds or anyone feels these symptoms, get everyone outside to fresh air, then call 911; CPSC's 2026 release says never to ignore an alarm.

What should you do when the power comes back?

When the power comes back, let the system restart on its own and check that it is safe to run. Ready.gov says to turn off or disconnect appliances and electronics during the outage because power "may return with momentary surges or spikes."

Then walk outside and look at the furnace's two plastic vent pipes. A storm that knocks out power often buries vents, and furnace makers mount them 12 inches or more over the likely snow depth; clear packed snow by hand or with a soft brush. Check the thermostat, and if the furnace does not start, work through the no-heat checklist before calling a technician. Lennox's manual says not to use a furnace if any part has been underwater.

Check the house for frozen or leaking pipes, especially in cabinets on outside walls. If you are unsure about anything near the equipment, stop and call a qualified technician. The cold snaps overview links the rest of this section.

Lift-line questions

Where to go from here

• Folder: All the cold-weather pages in one place
• Cold snaps: Preventing and thawing frozen pipes
• Cold snaps: Safe checks when the furnace stops
• Indoor air: Carbon monoxide safety in Colorado homes