Power station runtime calculator

Enter the power station's watt-hours and its AC output and surge ratings, then list what you want to run. You get the hours each appliance runs on its own and all together, and a check that the station can carry and start them.

Inputs

Watt-hours on the label. EcoFlow’s DELTA 2 is 1,024 Wh, Bluetti’s Elite 100 V2 is 1,024 Wh, its Elite 300 is 3,014 Wh.

The most the AC outlets deliver at once. EcoFlow’s DELTA 2 is 1,800 W.

What it can deliver for a moment, to start a compressor. DELTA 2: 2,700 W; Bluetti Elite 100 V2: 3,600 W.

EcoFlow suggests 80–90% for AC and uses 85%; Bluetti’s fridge guide uses 80%. Use 100% for devices on the DC or USB ports.

Set 80% to keep a reserve (EcoFlow’s test plan runs from 100% down to 20%). Bluetti’s guide assumes 80–95% of a lithium battery is usable.

Its screen, battery management and fans use power even when nothing is plugged in: about 15 W for Bluetti’s Elite 300, 7.5–13 W for its EB3A.

What you want to run

Running watts from the label. "Time on" is the share of the time it draws that power: a fridge compressor runs about 30–50% of the time, most other things 100% while in use. Startup watts only for motors and compressors.

Runs everything for

5.4hours

5.4 hours from 1,024 Wh (100% used at 85% efficiency) at 150 W average plus 10 W for the station itself.

It runs everything, for about 5.4 hours. That is less than a night; add capacity or leave something out.

Energy you get
870 Wh
Average draw
160 W
All on at once
270 W
Surge needed
1,070 W
How long each appliance runs the station, and all of them together

A 1,024 Wh power station gives 870 Wh after the share you use and its efficiency. 3 appliances average 150 W and the station itself draws 10 W, so everything together runs for about 5.4 hours. Each on its own: Refrigerator 9.7 hours; Wi-Fi router 43.5 hours; Laptop and phone 12.4 hours. At full power they draw 270 W against the 1,800 W output, and the worst startup needs 1,070 W against 2,700 W of surge. It runs everything, for about 5.4 hours. That is less than a night; add capacity or leave something out.

Safety first

A power station holds a lot of energy and makes mains voltage, and an overloaded or badly connected one can overheat. The cords and connections to what you run are part of the circuit.

  • Fuse every circuit you add. If you wire a power station or its battery into a van, boat or cabin, fuse the cable at the battery and size the cable for the current. Use the fuse and cable the maker specifies.
  • Follow the manufacturer’s instructions for the station, including its rated power, ventilation, charging and the ports it allows for each load.
  • Follow your local electrical code. Do not connect a power station to a house’s wiring through a plug or a “backfeed” cable. A transfer switch or an interlock, installed to the code, is the safe way.
  • Have a qualified person check the installation of anything that is wired in, and keep the station dry and in free air while it runs.

How it works

energy you get = capacity × share you use × efficiency
runtime        = energy you get ÷ (average load + the station’s own draw)
average load   = running watts × time on (the duty cycle)
it runs        = running watts ≤ AC output, and the biggest startup fits the surge rating
  • Efficiency is 85% by default, EcoFlow’s example, inside its 0.80–0.90 range for AC. Use 100% for devices on the DC or USB ports.
  • The share you use is 100% by default. EcoFlow’s test plan runs from 100% down to 20%, and Bluetti’s guide says 80–95% of a lithium battery is usable, so set a lower figure to keep a reserve.
  • The duty cycle is the share of the time an appliance draws its running watts. A refrigerator’s compressor cycles, at 30–50% of the time (Bluetti; 40% by default here). Most other things run at 100% while in use.
  • The surge check assumes the biggest motor starts while everything else is already running, the same rule as the inverter calculator.

Worked example

A 1,024 Wh station with 1,800 W of AC output and a 2,700 W surge, running a refrigerator (200 W, 40% of the time, 1,000 W to start), a Wi-Fi router (10 W) and a laptop (60 W).

  • Energy you get: 1,024 × 0.85 = 870 Wh.
  • Average draw: 200 × 0.4 + 10 + 60 = 150 W, plus 10 W for the station itself, 160 W.
  • Everything together runs for 870 ÷ 160 = 5.4 hours.
  • The fridge alone, with the 10 W of idle draw, runs 870 ÷ 90 = 9.7 hours. The router alone runs 43.5 hours and the laptop alone 12.4.
  • At full power the three draw 270 W, far inside 1,800 W, and the fridge starting adds 1,000 W on top of the 70 W already running, 1,070 W, inside the 2,700 W surge rating.

Tips from the road

  • Measure your fridge. A plug-in watt meter over a day gives the real average draw. Bluetti’s guide says a 500 W-rated fridge averages 150–250 Wh an hour, and EcoFlow’s own log shows measured runtimes shorter than the estimate.
  • Run small loads on the DC ports. EcoFlow says phones, routers and similar gear on DC or USB-C avoid the inverter losses and last longer.
  • Do not open the door. Every opening raises the duty cycle, and a hot room raises it a lot.

FAQ

How long will a power station run a refrigerator?

Multiply the capacity by about 0.85 and divide by the fridge's average draw. A fridge rated at 200 W that runs 40% of the time averages 80 W, so a 1,024 Wh station gives 1,024 × 0.85 ÷ 80 = 10.9 hours before the station's own idle draw. Bluetti's guide says a compressor runs 30–50% of the time at normal room temperature, and up to 80–90% above 90 °F.

Why is 0.85 used?

The station stores DC power and the AC outlets run it through an inverter, which loses part of it as heat. EcoFlow says to use 0.80 to 0.90 for AC as a first pass and uses 0.85 in its example; Bluetti's fridge guide uses 0.8 and its 3 kWh guide says 85–95% for its inverters. Devices on the DC or USB ports lose less.

Why does the calculator say my fridge is too much for the station?

A compressor needs a burst of power to start, often two to three times its running watts (Bluetti). The station must supply that surge as well as the other loads that are already running, and its surge rating is the limit. If the surge or the running total is above its rating, the station shuts down on overload.

What is the station's own draw?

The screen, battery management system and fans use power even with nothing plugged in. Bluetti gives about 15 W for the Elite 300 and 7.5–13 W for the older EB3A. It matters most for small loads, where it can be a large share of the draw. This page adds it to the load, as Bluetti's formula does.

How long does a fridge stay cold with no power?

Bluetti's guide says an unopened refrigerator keeps food safely cold for only about four hours and a full freezer for up to 48 hours, which is why runtime matters most for the fridge. Keep the door shut and check your own appliance's guidance.

Sources

  1. Test Your Power Station Runtime Before an Emergency, EcoFlow. Runtime ≈ battery capacity × assumed efficiency ÷ average load; use 0.80–0.90 for AC as a first pass; 700 Wh × 0.85 ÷ 70 W ≈ 8.5 hours; DC ports skip the inverter losses; plan from 100% down to 20%.
  2. How Long Can a BLUETTI Power Station Power a Full-size Refrigerator?, Bluetti. The formula (Battery Wh × 0.8) ÷ Running Watts; a refrigerator compressor runs 30–50% of the time (40% as the benchmark) and above 90 °F 80–90%; the starting surge is two to three times the running watts; Elite 100 V2 is 1,024 Wh, 1,800 W and 3,600 W of surge.
  3. How Long Will a 3kWh Power Station Last?, Bluetti. Runtime = (capacity × depth of discharge × inverter efficiency) ÷ (load + self-consumption); 3,014 Wh at 95% and 90% gives 2,577 Wh, 17.2 hours at 150 W and 15.6 hours with the Elite 300's 15 W idle draw.
  4. EcoFlow DELTA 2 user manual, EcoFlow. Specifications - 1,024 Wh; AC output 1,800 W total, surge 2,700 W, with an X-Boost mode (2,200 W maximum) for heating devices.

Formula and sources last checked September 30, 2026. How we test formulas.

  • Off-grid solar system builderList your loads and size the whole off-grid system at once, with battery amp-hours, solar watts, inverter size, main cable gauge and a 24-hour charge chart.
  • Amp-hour and battery runtime calculatorHow long a battery runs a load. Enter amp-hours, voltage, battery type and watts. Covers LiFePO4 and AGM, inverter losses and lead-acid discharge-rate loss.
  • Inverter size calculatorWhat size inverter you need for a van, RV or cabin. Continuous watts for what runs together, surge watts for the biggest motor starting, and battery current.
  • Battery bank size calculatorHow many amp-hours of battery you need for an RV, van, boat or cabin, from your daily watt-hours and days of autonomy, with a 24-hour state-of-charge chart.
  • DC wire size and voltage drop calculatorFind the AWG wire size for a 12, 24 or 48 V DC circuit from current and distance. Checks voltage drop and ampacity with NEC and Coast Guard tables.
  • Solar charge controller size calculatorWhat size solar charge controller you need, MPPT or PWM: its amp rating, the voltage it must take on a cold morning and the PV fuse, from your panels.

Safety note: Estimates only. Equipment ratings vary by manufacturer, so always follow the manufacturer’s instructions and ratings, and ask a qualified professional when safety is at stake.