How long will a power station or home battery run your fridge, Wi-Fi, CPAP or lights during a power outage? This free power station runtime calculator adds up your devices, accounts for inverter losses and battery type, and shows the real runtime in hours, whether the inverter can handle the startup surge, and how fast solar panels can recharge it.
Power Station Runtime Calculator
How long a battery backup will keep your devices running during an outage.
Runtime = capacity × usable depth of discharge × efficiency ÷ average watts. Fridges and pumps cycle on and off, so their average draw is far below their label rating. Solar recharge assumes 75% real-world panel output.
How to Use the Power Station Runtime Calculator
- Pick your battery capacity in watt-hours (Wh), or type the exact number from the label.
- Enter the inverter’s continuous AC output in watts.
- Choose the battery type and whether devices use the AC outlets or DC/USB ports.
- Use + and − to add every device you want to run at the same time.
- Choose your solar panel wattage to see the recharge time.
How to Calculate Battery Runtime
Runtime (hours) = battery capacity (Wh) × usable depth of discharge × inverter efficiency ÷ device watts
Inverters that turn battery power into AC lose about 10 to 15% as heat, and lead-acid batteries should only be drained to 50%. Lithium iron phosphate (LiFePO4) batteries, used in most modern power stations, can safely use almost their full rated capacity.
Example: a 1,024 Wh LiFePO4 power station running a fridge (60 W average), Wi-Fi (15 W), a laptop (50 W), two phones (20 W) and three LED bulbs (27 W) uses 172 W on average. 1,024 × 0.95 × 0.85 ÷ 172 = about 4.8 hours.
How Long Will a Power Station Run a Refrigerator?
| Battery capacity | Fridge only (~60 W avg) | Wi-Fi + 1 LED bulb (~24 W) | CPAP (~40 W) |
|---|---|---|---|
| 256 Wh | 3.4 h | 8.6 h | 5.2 h |
| 512 Wh | 6.9 h | 17 h | 10 h |
| 1,024 Wh | 13.8 h | 34 h | 21 h |
| 2,048 Wh | 27.6 h | 2.9 days | 41 h |
| 3,600 Wh | 2 days | 5 days | 3 days |
Figures use AC output with 85% inverter efficiency and 95% usable LiFePO4 capacity. A modern fridge is rated at 100 to 200 W but its compressor cycles on and off, so it averages about 1 to 1.5 kWh a day.
Running Watts vs Surge Watts
Every power station lists a continuous output (for example 1,800 W) and a higher surge or peak output. Motors in fridges, freezers and pumps need a short burst of 3 to 8 times their running power to start. If the surge is higher than the inverter can supply, the unit shuts off. For whole-home backup or bigger loads, compare with our generator size calculator.
How to Make Your Battery Last Longer in an Outage
- Run the fridge, Wi-Fi and medical devices first; skip heaters, kettles and hair dryers.
- Use DC or USB ports for phones, routers and LED lights to avoid inverter losses.
- Keep the fridge door closed and set it to 37°F (3°C) to cut compressor run time.
- Add solar panels so the battery refills every day. Size a full rooftop system with the solar panel calculator.
- Store the power station at 50 to 80% charge and top it up every few months.
Frequently Asked Questions
How long will a 1000Wh power station run a refrigerator?
About 12 to 14 hours. A typical fridge averages around 60 W, and a 1,000 Wh LiFePO4 power station delivers about 800 Wh through its AC inverter.
How do I calculate how long a battery will last?
Multiply the capacity in watt-hours by the usable share (about 0.95 for LiFePO4 or 0.5 for lead-acid) and by inverter efficiency (about 0.85), then divide by the total watts of your devices.
Can a power station run a CPAP all night?
Yes. A CPAP without a heated humidifier uses about 30 to 60 W, so a 500 Wh power station runs it for roughly 8 to 10 hours. Using the humidifier can double the power draw.
What size power station do I need for a power outage?
For essentials like a fridge, Wi-Fi, phones and a few lights for 24 hours you need about 2,000 to 3,000 Wh. For a single night of CPAP or Wi-Fi, 500 to 1,000 Wh is usually enough.
How long does it take to charge a power station with solar?
Divide the battery capacity by about 75% of the panel wattage. A 1,024 Wh unit with 200 W of panels needs roughly 7 hours of good sun, or one and a half to two days.
More Free Home Calculators
- Generator Size Calculator – running and starting watts for backup power
- Solar Panel Calculator – how many panels you need, cost and payback
- Appliance Energy Cost Calculator – what each appliance costs to run
- Internet Speed Calculator – the Mbps your household really needs
- Paint Calculator – how many gallons of paint a room needs
