How the calculator works
The calculator starts with rated battery capacity, then adjusts for current charge, battery health, reserve, and conversion efficiency before dividing usable energy by average appliance load.
Portable power station runtime calculator
Estimate battery runtime and the power station size your appliances need.
Enter your battery capacity, appliance watts, duty cycles, reserve, battery health, and inverter efficiency to get a practical runtime estimate with the math shown.
Power station
Appliances
Power station runtime basics
Why advertised Wh differs from usable Wh
A 1000Wh battery rarely delivers a full 1000Wh to appliances because reserves, conversion losses, battery age, and internal electronics reduce usable output.
AC inverter losses
AC outlets use an inverter to convert battery DC power into household AC power. That conversion commonly loses energy as heat.
AC vs DC efficiency
DC and USB loads can be more efficient because they may avoid the main AC inverter. Use a higher efficiency value when your setup is mostly DC.
Battery reserve
Leaving a reserve helps prevent unexpectedly draining the station to zero and gives a more conservative planning number.
Battery degradation and health
Older batteries can store less energy than their original rating. Lower the health percentage when estimating with a used or heavily cycled station.
Appliance duty cycles
Some appliances, such as refrigerators, cycle on and off. Duty cycle estimates the percentage of time they draw their running watts.
Startup and surge watts
Motors and compressors may need a brief startup surge higher than their normal running watts. Check both continuous and surge ratings.
Common runtime examples
A router may run for days on a 1000Wh station, while a microwave or space heater can drain the same battery quickly because high-watt heat loads consume energy fast.
FAQ
How long will a 1000Wh power station last?
Divide usable watt-hours by average load. With 85% efficiency and no other adjustments, a 1000Wh station provides about 850Wh usable, so a 100W load may run about 8.5 hours.
How do I calculate power station runtime?
Estimate usable battery Wh after charge, health, reserve, and efficiency, then divide by the total average watts of your appliances.
Why does not a 1000Wh battery provide exactly 1000Wh?
Inverter losses, manufacturer reserve, battery age, temperature, and internal electronics all reduce the amount of energy delivered to your devices.
How much power does a refrigerator use?
Many full-size refrigerators run around 100W to 200W while the compressor is on, but the average can be lower because the compressor cycles.
What size power station do I need?
Add your appliance average watts, multiply by desired hours, then increase the capacity estimate for efficiency losses, reserve, and battery health.
What are surge watts?
Surge watts are short startup loads required by some appliances, especially motors and compressors. The power station must tolerate that brief peak.
Does a power station lose energy through the inverter?
Yes. AC inverter conversion usually loses energy, so AC loads generally deliver less usable runtime than a perfect Wh rating suggests.
Is DC more efficient than AC?
Often, yes. DC and USB outputs may avoid the main inverter, but actual efficiency depends on the power station design and the connected device.