How long can your battery run what you need?
Pick what you own and what you need to keep on. No watt-hours, no amp-hours, no math.
A Jackery Explorer 300 says 293 Wh on the label, and about 237 Wh of that actually reaches a plug. That runs a full-size fridge for roughly 5 hours, a CPAP for about 6 hours, a wifi router for more than a day, and a 1500 W space heater for about 10 minutes. The part most calculators skip is start-up. A fridge compressor needs roughly 800 W for a split second to kick on, and a 300 W power station that peaks at 600 W simply refuses.
293 Wh · 300 W continuous · tap to change
Anything else on it?
2 hr 47 min
Jackery Explorer 300, running full-size refrigerator, two phones charging, wifi router + modem.
This battery probably cannot start your full-size refrigerator. It surges to 600 W. A full-size refrigerator needs roughly 835 W for a moment to kick on. It will run the smaller things on the list fine.
The other half of the answer
That is one appliance. How many days of power do you actually have?
Most homes have no emergency source of power when they need it. Provision Planner keeps track of the power you have and helps you build it up before you need it.
About 2 minutes.
What would actually change this
| If you had | Runtime | Starts it |
|---|---|---|
| What you have now | 2 hr 47 min | No |
| A second Jackery Explorer 300twice the hours, same start-up problem | 5 hr 34 min | No |
| A Goal Zero Yeti 500X insteadthe smallest one that actually starts it | 4 hr 28 min | Yes |
| A Jackery Explorer 1500 Pro insteadcarries it overnight | 14 hours | Yes |
| Any of the above, plus solar | Indefinite, sun allowing | Unchanged |
Solar is the only row that puts energy back in. The rest just start the outage with more of it.
What this assumes
- A full-size fridge draws about 150 W while the compressor runs, and it runs roughly a third of the time, so 50 W is the honest hourly average.
- 85% inverter efficiency, and 95% of the 293 Wh on the label as genuinely usable, which gives 237 Wh to spend.
- Your own appliance, your climate and how often the door opens will all move this. It is a close estimate, not a promise.
Before the next outage
Most homes have about three days of food and water in them.
Provision Planner counts yours and tells you the number: days of food and water covered for your household, what expires when, and what to buy next. Your power is one line in it.
About 2 minutes. Nothing to install.
What drains a battery fastest
Anything that makes heat. A space heater, a kettle, a hair dryer and a microwave all turn electricity into warmth about one watt for one watt, so they empty a power station in minutes. Motors come second, because starting one costs several times what running it does. Lights, routers and phones barely register next to either. You can keep a house lit and online on a battery that could not boil a single cup of water.
Why the label lies a little
A battery marked 293 Wh does not hand 293 Wh to a plug. Turning stored DC into household AC burns about 15% as heat, and lead-acid should never be run flat, so a car battery gives up maybe a third of its rating before you risk not starting the car. Every figure here is worked out after those losses, which is why it sits below the number on the box.
The 5 people ask about most
Provision Planner
See exactly where your household stands.
Provision Planner counts what is already in your house and tells you how many days of food, water and power it covers for the people who live there, what expires next, and what to buy this month.
See how long my preps will lastAbout 2 minutes. Nothing to install.
Battery figures come from manufacturer specs for 45 models across Jackery, EcoFlow, Goal Zero, Anker and Bluetti, plus generic car and deep-cycle setups. Where a brand advertises a boosted output mode, we use the lower rating. Appliance draws are typical household figures, shown on the page with the reasoning behind them rather than buried. If the power is out right now, the live power outage map shows what is reported near you, and how long a freezer stays cold without power covers the food side.
About medical devices. These figures are planning estimates, not medical advice, and nothing here should replace guidance from your doctor or your equipment supplier. If anyone in your house relies on a CPAP, an oxygen concentrator or any other powered medical device, confirm the power requirements in that manufacturer's own documentation and arrange backup power with them. Do not use this page to decide whether a device will keep someone safe.