Free calculators and plain-language guides
Know what you can keep running when the power goes out.
Add up your essentials, size a generator or power station, and work out how long it will last. No sign-up, and nothing leaves your browser.
What do you need to run?
Tap to switch onExample watts with 20% headroom. The surge figure assumes only the largest motor starts while the rest are running. Use your own numbers in the full calculator.
Calculators
Each one answers a single question and shows the working, so you can check it against your own equipment.
Generator sizing
Estimate continuous output and the extra start-up surge from motors and compressors.
Open calculator →Battery runtime
Enter watt-hours and your average load to see how many hours you get against your target outage.
Open calculator →Fuel planner
Work out how much gas or propane to store for a one, three or seven day outage.
Open calculator →Solar recharge
See what your panels realistically put back in a day, including a low-sun winter scenario.
Open calculator →Load builder
Pick appliances, set hours of use, and compare an essentials plan with added comforts.
Open calculator →Fridge and freezer
Turn daily energy use and outage length into a battery size, with a reserve built in.
Open calculator →The lights just went out. Start here.
A short order of operations for the first hour, written for a phone screen and a flashlight.
- Check whether it is just you. Look at your breaker panel, then the neighbours, then your utility's outage map.
- Keep the fridge and freezer shut. Every time the door opens, the safe window gets shorter.
- Unplug sensitive electronics. Power can surge when it comes back on.
- Run generators outdoors only. Never in a garage or shed. Keep them at least 20 ft (6 m) from the house, and have a working carbon monoxide alarm.
Guides
Longer reads for the decisions a calculator cannot make for you.
Power station or generator: which fits your home?
Noise, fuel, indoor use and running time, compared side by side.
SafetyGenerator safety: carbon monoxide, cords and backfeeding
The mistakes that hurt people, and how to set up so you avoid them.
WinterKeeping the furnace running in a cold-weather outage
What a gas furnace draws, how to power it safely, and how to protect pipes.
How-toHow to measure what your appliances really use
Plug-in meter, energy label or nameplate, and which number goes in which calculator.
Gear, sized to your numbers
Run a calculator first, then compare equipment that meets the size it gives you.
Portable power stations
Silent and safe indoors. Best for fridges, routers, lights and medical devices.
What to check →Safety and small essentials
Carbon monoxide alarms, an energy meter, fridge thermometers and a lantern.
What to check →Disclosure: as an Amazon Associate, PowerOutageKit earns from qualifying purchases. Retailer links on the gear page are affiliate links, at no extra cost to you. Calculators and guides are free and are not influenced by commissions.
How this site works
PowerOutageKit is an independent, one-person site for households in the United States and Canada. It exists to help you work out your own numbers before you spend money on backup power.
Every calculator runs in your browser and shows its formula with a worked example. The appliance figures offered as starting points are examples, and you can replace each one with a reading from your own equipment. Safety guidance is drawn from government sources in both countries and linked from each guide.
The site does not test or rank products, and it does not give wiring advice. Read more about how it is run.