What to Power During a Power Outage (and What to Skip)

The first things to power in an outage are the ones that keep people safe: medical equipment, phones, a few lights, and the refrigerator. Heat or cooling for vulnerable family members and a sump pump come next, and everything else can wait. The hard part is matching that list to a generator or battery that can start those loads without overloading, and doing it without carbon monoxide or backfeed risks.

What Should I Power First During a Power Outage?

Power the things that protect health and let you get information. Comfort items come last. Ready.gov and the CDC both stress medical needs, communication, and food safety in their outage guidance.

1. Medical devices. This includes oxygen concentrators, CPAP machines, powered beds, and refrigerated medicine. Talk to your doctor and device maker about backup plans before an outage.
2. Phones and a modem or router. These draw little power and keep you connected to alerts and utility updates.
3. A few lights. LED bulbs or lamps in the rooms you actually use. Skip whole-house lighting.
4. Refrigerator. Then the freezer if you can afford the load.
5. Sump pump. A failed pump during a storm can flood a basement fast.
6. Heating or cooling for vulnerable people. Think infants, older adults, and anyone with a heat or cold-related health risk. Use the smallest safe option, such as a fan or one room heater, not whole-house systems.

Everything else, like TVs, game consoles, dryers, ovens, and electric water heaters, waits. These are big draws or small comforts, and they can overload a small source quickly.

What Appliances Can a Portable Generator Run?

A portable generator can run any appliance whose running watts, plus the biggest startup surge, fit inside the generator’s rated output. The catch is that motors need far more power for a moment when they start.

Running watts are what a device uses continuously. Startup (or surge) watts are the short spike when a motor kicks on, like a refrigerator compressor or sump pump. Many appliance lists show only one number, which is how people end up with an overloaded generator. The figures below are typical ranges. Always check the nameplate on your own equipment.

Notice the space heater. It has no startup spike, but it draws a steady 1,500 watts on its high setting. That alone can drain a small battery in under an hour. Resistance heat is expensive to back up. A warm room, blankets, and a safe shelter plan usually work better.

What Is Power In, Power Out?

“Power in, power out” means the energy going into a system must cover the energy coming out, plus losses. For a generator, fuel is the power in and the outlets are the power out. For a battery, the stored watt-hours are the power in and the inverter’s AC output is the power out.

Here is a simple example. Say you have a 1,000-watt source. You can run a 150-watt refrigerator, a 50-watt set of lights, and a 20-watt router at once, because the total of 220 watts is well under 1,000. Add a 1,500-watt space heater and the total hits 1,720 watts. The source cannot supply that. A generator will trip or stall, and a power station will shut off to protect itself.

Batteries add a second limit: time. Runtime depends on three things.

• Watt-hours (Wh): the size of the “tank.”
• Load in watts: how fast you drain it.
• Inverter losses: converting battery power to AC wastes some energy. A common planning assumption is 10-15% loss, so I use 15% below.

Formula: runtime in hours = (battery Wh × 0.85) ÷ load watts. A 1,000 Wh station running a steady 220 watts gives about 3.9 hours (1,000 × 0.85 ÷ 220).

How Do I Calculate the Generator or Power-Station Size I Need?

Add the running watts of everything you will run together, add the largest single startup surge, then add about 20% as a safety margin. That gives the minimum output rating you need. A separate watt-hour calculation tells you the battery size for your runtime.

Step 1: Output size (watts)

Our example household wants a refrigerator, five LED bulbs, a modem and router, and a CPAP. These figures are assumptions. Use your own nameplate numbers.

• Refrigerator: 150 W running, 600 W startup
• Five LED bulbs: 50 W
• Modem and router: 20 W
• CPAP with humidifier: 40 W

Total running watts: 150 + 50 + 20 + 40 = 260 W.

Add the largest startup surge: 260 + 600 = 860 W. This method slightly overcounts, since the refrigerator’s running watts are counted twice. That is fine. It builds in caution.

Add a 20% margin: 860 × 1.2 = about 1,030 W. A source rated for at least 1,200 watts of continuous output is a sensible pick. If you add a sump pump with a 1,800 W startup, redo the math: 260 + 800 (pump running) + 1,800 (largest surge) = 2,860 W, and with a margin about 3,430 W. That needs a real generator, not a small battery.

Step 2: Battery size (watt-hours)

Estimate hours of use per day for each item, with these assumptions:

• Refrigerator: 150 W × 8 hours of compressor run time = 1,200 Wh
• Lights: 50 W × 5 hours = 250 Wh
• Router: 20 W × 24 hours = 480 Wh
• CPAP: 40 W × 8 hours = 320 Wh

Daily total: 2,250 Wh. Divide by 0.85 for inverter losses: 2,250 ÷ 0.85 = about 2,650 Wh per day. A 1,000 Wh station covers only part of a day. A 2,000 to 3,000 Wh station covers about a day, and then you need to recharge.

How Do I Connect a Generator Safely Without Backfeeding the House?

Use a transfer switch or interlock kit installed by a licensed electrician. Never plug a generator into a wall outlet with a homemade cord. That sends power back out through the service lines, which can seriously injure or kill utility workers, and it can damage the generator and start fires.

Here is the problem with placement. The generator must sit outdoors, at least 20 feet from windows, doors, and vents, according to Ready.gov’s power outage guidance. It must never run inside a home, basement, garage, or carport, even with doors or windows open. That makes a long cord run through a window tempting, but it is not a safe plan. The safer solution is a permanent power inlet box on an outside wall, wired to a transfer switch, both installed by a licensed electrician. Extension cords are not a substitute for that setup.

Fuel handling matters too.

• Turn the generator off and let it cool before refueling.
• Store fuel in approved containers, outside living spaces.
• Use a battery-powered or battery-backup carbon monoxide detector inside the home.

Can I Use a Gas Stove, Oven, Grill, or Car to Heat My Home?

No. Gas stoves and ovens, charcoal grills, camp stoves, and idling cars all produce carbon monoxide (CO), which can kill you before you notice. The CDC’s carbon monoxide guidance warns against all of these indoors or in attached spaces.

Grills and camp stoves belong outdoors, at least 20 feet from windows and other openings. Never run a car in a closed garage, even with the door cracked. If it is cold, layer clothes, close off one small room, and go to a warming shelter if you can. If anyone feels dizzy, gets a headache, or feels sick, get to fresh air and call 911.

What Should You Not Do During a Power Outage?

Do not run fuel-burning equipment indoors, do not heat with an oven, and do not connect a generator to the house with unsafe wiring. Each of these has caused injuries and deaths in past outages.

• Don’t run a generator in a garage, basement, or carport. CO builds up fast.
• Don’t backfeed. No male-to-male cords into a wall outlet.
• Don’t overload the source. Keep total load under the rated output, startup surge included.
• Don’t refuel a hot generator. Fuel vapor can ignite on hot parts.
• Don’t use candles when you can avoid it. Battery lanterns and flashlights are safer.
• Don’t open the refrigerator and freezer repeatedly. Each opening lets cold air out.
• Don’t touch downed power lines. Stay far back and report them to the utility or 911.

Should I Unplug Things During a Power Outage?

Yes, unplug sensitive electronics and appliances you are not using. When power returns, it can arrive as a surge or flicker that damages TVs, computers, and appliance control boards. Ready.gov notes that unplugging helps, and that surge-protection devices add more protection.

But not everything should come off. Keep these connected to your backup source:

• Medical equipment, plugged into the backup source, not the wall
• The refrigerator and freezer, if your source can run them
• One lamp left switched on, so you know when grid power returns

Unplug computers, TVs, game consoles, microwaves, and washers. If the refrigerator is on grid power, leave it plugged into a surge protector rated for appliances, or unplug it and plug it back in only after power has been stable for several minutes. Some compressors dislike being restarted quickly, so wait a few minutes before reconnecting.

How Long Will Food Last Without Power?

A closed refrigerator keeps food safe for up to 4 hours. A full freezer holds for about 48 hours, and a half-full freezer for about 24 hours, if the door stays closed. These are the CDC’s figures from its power outage safety guidance.

After the refrigerator has been without power for 4 hours or more, discard perishable foods like meat, poultry, fish, eggs, and cut produce. When in doubt, throw it out. A food thermometer helps, since you can check items against safe temperatures instead of guessing.

This is why the refrigerator ranks high on the priority list. A 150 W refrigerator on a 2,000 Wh battery can stretch your food window into days. A freezer packed with food holds cold longer, so fill empty space with containers of water ahead of time.

Is There Supposed to Be a Power Outage Today?

Check your utility’s outage map or planned-outage page. Planned outages, like maintenance or line upgrades, are usually announced ahead by mail, email, or text. Unplanned outages show up on the map as active incidents with an estimated restoration time.

Not every blackout is a utility outage. Use this quick check:

1. Look outside. If neighbors’ lights are on and yours are off, you likely have a tripped breaker or a main breaker problem. Check your panel.
2. If the whole street is dark, open your utility’s outage map or app. Report the outage if it is not listed.
3. Sign up for text alerts from your utility ahead of time.
4. Check local emergency information (city or county alerts, local radio) for broader grid events such as storms or heat emergencies.

If you see sparks, a burning smell, or downed lines, call 911 and stay away. Do not reset a breaker that keeps tripping. Call a licensed electrician.

One-Page Outage Checklist

Before the outage

• Write your top loads and their watts. Check nameplates.
• Charge power banks and power stations. Fill fuel containers safely if you own a generator.
• Test CO detectors and put in fresh batteries.
• Sign up for utility text alerts. Save the outage hotline number.
• Put a thermometer in the refrigerator and freezer. Freeze water containers.
• Ask a licensed electrician about a transfer switch if you use a generator.

First 15 minutes

• Check the breaker panel and neighbors’ lights.
• Check the utility outage map. Report the outage.
• Start medical backup power if needed.
• Unplug TVs, computers, and appliances you are not using.
• Keep the refrigerator and freezer doors closed. Note the time.

While power is out

• Run generators outdoors, 20 feet from windows, doors, and vents.
• Keep total load below the source’s rating.
• Use flashlights and battery lanterns instead of candles.
• Never heat with a stove, oven, grill, or car.
• Throw out perishables after 4 hours without refrigeration.

When power returns

• Wait a few minutes to be sure power is stable.
• Turn off the generator. Let it cool before refueling.
• Plug big appliances back in one at a time.
• Reconnect electronics last, preferably through surge protectors.
• Check food temperatures and discard anything unsafe.
• Restock fuel, recharge batteries, and note what you would change.

Frequently Asked Questions

What is power in power out?

It means the energy a system takes in must cover what it sends out, plus losses. A 1,000-watt generator can only safely deliver 1,000 watts at once, so loads above that will trip it. A battery adds a time limit: runtime equals watt-hours times about 0.85 for inverter losses, divided by the load in watts.

Is there supposed to be a power outage today?

Check your utility’s outage map and planned-outage notices. Planned work is typically announced in advance, and unplanned outages appear as active incidents. If neighbors have power and you don’t, check your breakers first.

What should you not do during a power outage?

Never run a generator, grill, or camp stove indoors or in a garage. Never heat with a gas oven or stove. Never plug a generator into a wall outlet, overload your power source, refuel a hot generator, or open the refrigerator more than needed.

Should I unplug things during a power outage?

Yes, unplug electronics and appliances you are not using, to protect them from a surge when power returns. Keep medical devices and your refrigerator connected to your backup source, and use surge protection for extra safety.

Wattfolk Editorial Team

The Wattfolk Editorial Team researches plug-in solar, home batteries and ways to cut electricity costs. Every guide is built from manufacturer datasheets, certification listings, government energy data, state laws and verified owner feedback, with the assumptions behind every savings estimate shown so readers can check the numbers for their own home.

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