Portable Power Station Runtime Calculator
Calculate your backup power before you buy. Use this portable power station runtime calculator to estimate how long a battery generator can run your phone, laptop, Wi-Fi router, mini fridge, CPAP machine, TV, refrigerator or other essential device.
Enter the battery capacity in watt-hours, the device wattage and the output type. The result is an estimated runtime. Actual results may vary based on battery age, temperature, inverter losses, device cycling, surge loads and the published specifications of your power station.
Runtime Calculator
Use rated battery capacity and typical device wattage. For refrigerators, freezers and other cycling appliances, use average running watts when possible.
How to Calculate Portable Power Station Runtime
The basic formula is simple:
Estimated runtime = usable watt-hours ÷ device watts
A power station rated at 1,024Wh does not always deliver the full 1,024Wh to your device. AC outlets use an inverter, and some battery capacity may be held in reserve by the battery management system. That is why this calculator lets you adjust usable battery percentage, output efficiency and reserve margin.
Quick Examples
| Power station size | Device load | Assumption | Estimated runtime |
|---|---|---|---|
| 300Wh | Phone charger, 10W | 85% efficiency | About 25 hours |
| 500Wh | Laptop, 60W | 85% efficiency | About 7 hours |
| 1,000Wh | Wi-Fi router, 15W | 85% efficiency | About 56 hours |
| 1,000Wh | TV, 100W | 85% efficiency | About 8.5 hours |
| 2,000Wh | Average refrigerator load, 150W | 85% efficiency | About 11 hours |
Typical Device Wattage Table
Use the label on your device or a plug-in watt meter when possible. The numbers below are typical device wattage ranges for planning only.
| Device | Typical wattage range | Notes |
|---|---|---|
| Smartphone charging | 5–20W | Small load; USB output is usually more efficient than AC. |
| Tablet charging | 10–30W | Depends on charger and battery level. |
| Laptop | 45–100W | Gaming laptops can use much more. |
| Wi-Fi router/modem | 10–25W | Good target for long backup runtime. |
| LED light | 5–20W | Runtime is usually long on battery power. |
| Box fan | 40–100W | Speed setting matters. |
| TV | 60–150W | Screen size and brightness affect load. |
| CPAP machine | 30–80W | Humidifier and heated hose can increase power use. |
| Mini fridge | 40–100W average | Compressor cycles on and off. |
| Full-size refrigerator | 100–250W average | Startup surge may be much higher than running watts. |
AC vs DC Runtime
Many portable power stations have AC outlets, USB ports and DC ports. If your device can run from USB-C or DC, it may avoid some inverter loss. If you plug a wall charger into an AC outlet, the battery must convert DC battery power to AC power and then the charger converts it again for the device.
For simple planning, this page uses 85% efficiency for AC output and 92% efficiency for DC or USB output. Those are planning estimates only. Check the published specifications for the model you own or plan to buy.
Why Your Real Runtime May Be Different
- Surge loads: refrigerators, pumps and some tools can need extra startup power.
- Battery temperature: very hot or cold conditions can reduce performance.
- Device cycling: refrigerators and freezers do not draw the same watts every minute.
- Inverter overhead: AC outlets consume some power even when the load is small.
- Battery age: older batteries may have less usable capacity than when new.
What Size Power Station Do You Need?
Start with the devices you must keep running. Add their typical wattage, decide how many hours of backup you need, then add a reserve margin. For home outage planning, many people separate devices into essential loads, comfort loads and optional loads.
| Use case | Common devices | Planning tip |
|---|---|---|
| Basic emergency kit | Phones, LED lights, radio | A smaller power station may be enough. |
| Work-from-home backup | Laptop, monitor, router | Calculate combined watts, not just laptop watts. |
| Medical comfort device planning | CPAP machine | Check device settings and talk to the device manufacturer for backup guidance. |
| Food protection | Refrigerator or freezer | Check running watts and startup surge. |
| Camping | Lights, fan, phone, small fridge | Solar charging can extend runtime during the day. |
Related Calculators
After this page, use these related calculators to plan more specific backup setups:
- CPAP Battery Runtime Calculator
- Refrigerator Backup Time Calculator
- Solar Charging Time Calculator
- Watts to Watt-Hours Calculator
FAQ
How many hours will a portable power station last?
Divide usable watt-hours by the watts your device uses. For example, a 1,000Wh power station running a 100W device through AC power might provide roughly 8 to 9 hours after efficiency losses. This is an estimated runtime, not a guarantee.
Why does a 1,000Wh power station not always deliver 1,000Wh?
Some energy is lost in conversion, especially when using AC outlets. The battery management system may also reserve some capacity to protect the battery.
Is AC or DC better for runtime?
DC or USB output is often more efficient when your device supports it. AC outlets are useful and flexible, but the inverter usually reduces runtime slightly.
Can a power station run a refrigerator?
Many larger power stations can run some refrigerators, but you must check both continuous wattage and startup surge requirements. Refrigerator runtime varies because the compressor cycles on and off.
Can I use this for CPAP backup planning?
Yes, as a planning estimate. Use the wattage for your exact CPAP setup and settings. Humidifiers and heated hoses can increase power consumption. For medical backup planning, confirm requirements with the device manufacturer or a qualified professional.
Does solar charging increase runtime?
Solar charging can extend runtime during daylight, but actual solar input depends on panel size, sun angle, weather, shading and charge controller limits. Use a solar charging calculator to estimate recharge time.
PowerStationCalc.com provides planning calculators and educational content. Calculations are based on typical device wattage and published specifications. Actual results may vary.