How to prepare for a power outage in winter

A winter outage is different from a summer one. The house goes cold, the well pump stops, and the plumbing starts to freeze while the roads are still closed. A standby generator helps only when it starts, the fuel flows, and the circuits you care about are on it.

This guide covers what fails first, how winter loads change the sizing math, and the checks that decide whether the unit carries the house or sits there clicking.

What fails first when the grid goes down

Heat is the first thing and the biggest thing. A gas furnace still needs electricity for its blower, control board, and igniter. A boiler needs power for its circulator. A heat pump needs power for the outdoor unit, the air handler, and, in cold weather, the electric resistance heat that backs it up. None of them run on fuel alone. NYSERDA puts it plainly: furnaces, boilers, and heat pumps all need electricity to start and to move heat through the house.

Water is second. Most private wells use an electric pump, often hardwired into the panel. When the power goes, the pump stops, and so does every faucet, toilet, and shower in the house. Portland General Electric notes that a well pump’s starting surge can be up to six times its running wattage, which is why a pump that draws little on paper can trip a generator that looked big enough.

Pipes are the expensive consequence. The pipes most likely to freeze run along exterior walls, in basements, attics, and under kitchen cabinets. Water expands as it freezes and splits the pipe, and the leak shows up when the thaw starts. The National Weather Service recommends keeping the faucet open and warming the pipe with a space heater, heating pad, hair dryer, or hot water on a cloth. Never use an open flame.

A standby generator does not back up the whole house by default. It backs up the circuits the installer moved to the transfer switch panel. Ask which of these are on it: furnace or boiler, well pump, refrigerator, and sump pump. If the furnace is not on the list, the generator will keep the lights on while the house freezes.

Size the generator for winter, not summer

The usual sizing conversation starts with the air conditioner. In a winter outage, the load that matters is heat. A gas furnace is a modest electrical load: a blower and controls, not a heating element. A heat pump is a different size of problem. Its compressor draws a lot, and when the outdoor temperature drops, the system calls on electric resistance auxiliary heat. Field data from the Department of Energy’s Cold Climate Heat Pump Challenge found auxiliary heat running about a quarter of the time in the coldest temperature bins, even on units designed for cold climates.

Resistance heat turns electricity into heat at close to a one-to-one ratio, so a few kilowatts of auxiliary heat can dwarf everything else in the house. If the strip is 10 kW and the generator was sized around a summer air conditioner, the math does not close. The nameplate on the air handler gives the strip size. The sizing calculator adds those loads up.

Two more winter loads are easy to forget. A well pump has a starting surge, and a sump pump can run for hours during a thaw. Both belong in the number. If you are still choosing a unit, compare standby generators by the natural gas rating, not the propane headline, because the same model makes less power on natural gas. The installed cost also changes with the fuel run and the size of the transfer switch.

Cold-weather readiness for the generator

Cold weather stresses the battery, the oil, and the fuel supply. Each has a check you can do before the storm.

Battery. A lead-acid battery makes less cranking current when it is cold. Generac recommends a cold weather kit for areas where temperatures fall below 32°F, and lists a battery pad warmer and an oil warmer for areas below 0°F. Check the date code, the terminals, and the charger status on the controller. Replace a battery more than a few years old before winter, not during the first outage.

Cold weather kit. The kit is not the same on every model. Generac’s cold weather kit contains the battery warmer. The extreme cold weather kit adds an engine block heater and calls for synthetic oil. A breather warmer is listed for areas with heavy icing. If your unit does not have one and you live where it regularly freezes, ask the installer what your model needs.

Oil. Generac’s manual for the 9 to 22 kW air-cooled units specifies synthetic SAE 5W-30 for all temperature ranges. Cold weather also shortens the service interval: below 40°F, the manual calls for an oil and filter change every year or 100 hours of operation. Check the level before the season and daily during a long outage, because the unit shuts down on low oil.

Natural gas. A piped supply does not run out, but it depends on the utility holding pressure. In a widespread cold snap, demand rises across the system, and utilities ask customers to cut back. UGI issues that request during extreme cold. Keep the meter and regulator clear of snow and ice so the regulator vent can breathe. If the generator stumbles or surges during an outage, call the utility and the installer. Do not adjust the regulator yourself.

Propane. Propane is liquid in the tank and has to boil into vapor before the engine can burn it. Cold slows that process, and the liquid needs heat from the tank walls to keep boiling. A low tank has less liquid surface in contact with the steel, and frost on the tank insulates it further. Tanks are filled to about 80% to leave room for expansion, so a 500 gallon tank holds roughly 400 gallons. Fill it before the season, not after the forecast turns. The propane burn-rate guide turns gallons into run time.

Exercise cycle. The unit should start itself on a weekly or biweekly schedule and run for about five to twelve minutes, depending on the model. That cycle charges the battery and proves the engine will start. If it has been failing, the controller will usually log it. Fix that before the storm. The maintenance guide covers the annual service.

Snow, ice, and the air the generator needs

A standby generator is outdoors for a reason. It needs air for combustion and cooling, and it needs to push exhaust away from the house. Snow works against both.

Generac’s manual requires airflow into and out of the unit to be unimpeded and asks for three feet of clearance around the intake and discharge louvers, free of shrubs and tall grasses. In winter, snow is the shrub. After a storm, clear the louvers, the top of the enclosure, and the pad. Do not shovel snow onto the unit, pile it against the sides, or build a shelter around it to keep the weather off. A shelter or wrap can trap exhaust.

Clear the gas meter and its regulator by hand or with a small broom. The Minnesota Department of Public Safety warns that ice or snow can block the regulator vent and cause a malfunction, and that a snow blower near the meter is dangerous. A shovel can damage the meter, so if you cannot clear it safely, call the utility.

Watch the roof. A snow slide or an icicle can damage the enclosure or block the exhaust, and a drift can bury the unit overnight. If the generator sits under a roof line, check it after every heavy snowfall, and check the propane tank and regulator too.

Carbon monoxide: the part that kills people

Carbon monoxide is colorless and odorless. The Consumer Product Safety Commission reports that more than 200 people die each year from accidental non-fire carbon monoxide poisoning tied to consumer products, and more than 100 of those deaths are linked to portable generators.

A standby generator vents outdoors, so it is safer than a portable unit in a garage. It is not risk-free. Exhaust can drift into a window, a door, or a fresh-air intake, and a snow-blocked exhaust can push carbon monoxide back toward the house. Placement and snow clearing matter.

Portable generators are the bigger hazard. Never run one inside a house, garage, basement, or crawlspace, even with the doors open. The CDC and Ready.gov both put the minimum at 20 feet or more from windows, doors, and vents, with the exhaust pointing away from the home. Never use a gas stove or oven to heat the house. If an alarm sounds, get everyone outside and call 911 from fresh air.

Test the alarms on every level and outside the sleeping areas before the storm, and replace them on the manufacturer’s schedule. The CDC recommends replacement every five years.

Pre-storm checklist

• Fill the propane tank. Clear the natural gas meter and regulator.
• Check the generator controller for alarms. Confirm the last exercise cycle ran.
• Check the oil level and the battery date. Replace a weak battery before the storm.
• Clear the three feet around the generator and look for snow or ice on the louvers.
• Test every carbon monoxide alarm. Replace the batteries if they are not sealed.
• Confirm which circuits are on the transfer switch: furnace or boiler, well pump, refrigerator, sump pump.
• Store water if you have a well. Portland General Electric suggests one gallon per person per day, plus water for animals.
• Know where the main water shutoff is. Open cabinet doors on exterior walls and let a faucet drip during extreme cold.
• Keep a path to the generator and the gas meter clear, and keep a broom, not a shovel, for the meter.
• Charge phones and power banks. Fill prescriptions. Put a flashlight in every bedroom.
• If the unit has not carried the house in a year, have the installer run a load test before winter.

When to call a pro

Clearing snow, checking oil, testing alarms, and reading the controller are homeowner work. Fuel lines, regulators, transfer switches, load calculations, and exhaust clearances are installer work. If the generator has not run under load, if the controller shows a fault you do not understand, or if the unit is more than a few years past its last service, call a local installer before the storm instead of after.

Use the installer directory to find someone who services your brand. If you are still planning the system, size it first, then read where to place a standby generator so the clearances and the fuel run are right before the pad goes in. The maintenance guide covers what the annual service should include.

A winter outage is survivable with a plan. The generator is one part of it. The fuel, the alarms, and the cleared exhaust are the parts that decide whether it works.