Winter storm power outage plan: what to power, in what order, for how many days
A priority list in watt-hours: refrigerator, CPAP, phones and sump pump before anything that makes heat, with USDA food windows and three-day battery math.
In February 2021 the Texas grid operator shed about 20,000 MW of load, the largest manually controlled load shed in United States history according to the FERC and NERC report on the event, and millions of households were without power for days in single-digit temperatures. That storm is the planning case for this page, not because it will repeat exactly but because it answers the question every winter outage asks: what do you actually need to run, and for how long. The honest order is water, food, medical equipment, communication, and then everything else, and heat is the one item a battery cannot carry.
The priority list, in watt-hours
Sized with this site’s usual arithmetic: the appliance’s real draw, a duty cycle, and 85% inverter efficiency. The usable capacity guide has the reasoning, the three-day plan runs the same list for four house sizes, and the solar guide prices the daytime recharge.
| Priority | Load | Draw | Per day at the outlet | Where the number comes from |
|---|---|---|---|---|
| 1 | Sump pump, if you have one and the ground is not frozen | 1,116 W at 25% duty | about 6,700 Wh | sump pump page |
| 2 | Refrigerator | 52 W average | about 1,250 Wh | refrigerator page |
| 3 | CPAP with humidifier | 53 W for 8 hours | about 425 Wh | CPAP page |
| 4 | Phones, router, modem | 20 to 40 W | about 500 to 900 Wh | nameplates |
| 5 | Lights, LED | 10 W each | under 100 Wh | nameplates |
| Not on the list | Space heater | 1,500 W continuous | 36,000 Wh | space heater page |
Without the sump pump, the essentials come to about 2,500 Wh a day at the outlet, roughly 3,000 Wh of usable battery. A 2 kWh class unit is most of a day; three days is a 4 kWh system with a solar or vehicle recharge, or two 2 kWh units. With a sump pump running in a wet winter the number roughly triples, which is why the pump gets its own page and its own battery. A household that wants the whole house through a week is in installed-system territory; the whole-house battery page covers that sizing.
Heat is a different plan
Look at the last row. A single 1,500 W heater draws more in an hour than the refrigerator, CPAP and phones together draw in a day. No portable battery carries it, and the space heater page shows the arithmetic. Winter heat in an outage comes from the house, not from electricity: close off one room, layer, use a heated blanket or mattress pad at roughly 180 W, which a battery does carry, and let the rest of the house get cold. If the home has a gas furnace, its blower and controls are a modest electrical load that a licensed electrician can put on a transfer switch; that is the one heating load a battery can plausibly run, and it is the electrician’s project, not a weekend one.
The two windows that do not wait
Food. USDA guidance is 4 hours for a closed refrigerator, 48 for a full freezer, 24 for a half-full one. In a hard freeze the porch is a refrigerator; in a mild one it is not, and a thermometer decides.
Medical equipment. A CPAP, an oxygen concentrator, a powered wheelchair charger or an insulin refrigerator gets sized first and its owner’s equipment provider gets told the plan before the season, not during the storm. The CPAP page is power math only, and so is this one.
Before the storm, in order
- Charge every battery to full and leave the units that have a UPS mode plugged in between the wall and the refrigerator or CPAP, so they take over without you.
- Fill the bathtub and a few containers if you are on a well; the well pump page explains why the pump is the hardest load in the house to back up.
- Put a thermometer in the refrigerator and one in the freezer.
- Set the generator, if you own one, outside where it will run, with the cord routed and the CO alarms tested, before the snow makes that a bad decision at midnight.
- Decide which room is the warm room and move the blankets there.
After the lights go out
Run the refrigerator and CPAP first, the phones and router in short sessions, and nothing that makes heat. Check the thermometers at the USDA windows. Recharge the batteries from a vehicle or solar during the day if the outage runs past the second night, and recharge them fully from the grid the moment it returns, because winter outages come in pairs.
Frequently asked questions
How big a battery do I need for a three-day winter outage?
For the essentials only, refrigerator, CPAP, phones and a router, about 2,500 Wh a day at the outlet, roughly 9 kWh of usable battery for three days, or a 2 to 4 kWh unit recharged from solar or a vehicle. Add a sump pump in a wet winter and the number roughly doubles. Heat is not on the list; a battery cannot carry it.
Can a portable power station heat a room in a winter outage?
No. A 1,500 W space heater empties a 2 kWh unit in a little over an hour. Heat comes from insulation, layers, a heated blanket at about 180 W, and one closed room; see the space heater page.
How long does food last in the refrigerator during a winter outage?
USDA guidance: about 4 hours with the door closed, 48 hours for a full freezer, 24 for a half-full one. In a hard freeze, a cooler on a porch keeps food cold longer than the refrigerator does without power.
Is it safe to run a generator during a winter storm?
Only outdoors, at least 20 feet from any window, door or vent, never in a garage even with the door open, and only with battery CO alarms inside. Winter storms are when carbon monoxide deaths from generators spike, because people bring them in out of the snow.