Emergency Backup Calculator

Emergency backup planning should show the essentials first and keep enough reserve for uncertainty.

Quick answers by battery size

Server-rendered examples using this scenario's sourced planning default. Use the calculator for your exact station and settings.

Assumptions: 500 W, 33% duty cycle, 85% AC efficiency, 10% reserve, new battery, no temperature loss.

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Runtime estimates by nominal battery capacity
Nominal capacity	Estimated runtime	Planning range	Static example
300 Wh	1h 23m	52m – 1h 44m	See Goal Zero Yeti 300 example
500 Wh	2h 19m	1h 27m – 2h 53m	See Goal Zero Yeti 500 example
1,000 Wh	4h 38m	2h 54m – 5h 45m	See Goal Zero Yeti 1000 LiFePO4 example
2,000 Wh	9h 16m	5h 48m – 11h 31m	See Jackery Explorer 2000 v2 example
3,000 Wh	13h 55m	8h 42m – 17h 16m	See Jackery Explorer 3000 Pro example

These are calculated planning estimates, not measured runtimes. Actual results vary with load, battery condition, temperature, and output path.

Review wattage sources and conditions

Calculator

Start with a quick estimate, then switch to Advanced if you need multiple devices, startup surge, battery health, or cold-weather loss.

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Power station model

Battery capacity (Wh): 1024 WhContinuous output rating (W): 1800 WSurge output rating (W): 2700 W

Estimated runtime4h 45m2h 58m – 5h 54m

Device scenario

Output path

Reserve kept unused (%)Cold weather loss (%)

Fridges cycle on and off. The calculator treats the entered wattage as compressor running wattage and applies a duty-cycle estimate.

Estimated runtime

4h 45m

This setup is tight. Reduce load, use DC where possible, or choose a larger station.

Conservative2h 58m

Estimated4h 45m

Optimistic5h 54m

Conservative assumes harder conditions; optimistic assumes favorable conditions.

This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
The largest startup surge (2900 W) is above the selected station surge rating (2700 W).

Usable energy: 783 Wh
Average load: 165 W
Fixed station overhead: Unknown (not included)
Running watts: 500 W
Max surge: 2900 W

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Rated Wh is reduced by efficiency, reserve, battery health, and temperature before it is divided by average load.

Rated battery: 1024 Wh; Battery capacity (Wh): 1024 Wh
Usable energy: 783 Wh; 1024 Wh x 85% x 90% x 100% x 100%
Average load: 165 W; 500 W running, 165 W average after duty cycle and quantity
Fixed station overhead: Unknown (not included); 165 W / 85% = 194.1 W battery draw; fixed overhead is unknown and excluded
Estimated runtime: 4h 45m; 783 Wh / 165 W = 4h 45m

1024 Wh nominal battery capacity
AC inverter output path
85% conversion efficiency
10% reserve kept unused
165 W average load from 1 load
100% battery health
0% temperature loss
Fixed station overhead unknown; not included

Shareable report link

This link contains the numeric values you entered, but not custom load names.

Source-Backed Next Steps

Need a size class?Open the size finder

Unsure about watts?Open the wattage chart

Charging with solar?Estimate solar offset

Plan a 24-hour fridge outagePlan 24-hour fridge runtime

Smallest matching record (8h)GRECELL 2400W

Estimated runtime

4h 45mThis setup is tight. Reduce load, use DC where possible, or choose a larger station.

Usable energy783 Wh

Average load165 W

Fixed station overheadUnknown (not included)

Running watts500 W

Max surge2900 W

Runtime range

Conservative2h 58m

Estimated4h 45m

Optimistic5h 54m

Show your work

Rated Wh is reduced by efficiency, reserve, battery health, and temperature before it is divided by average load.

Rated battery1024 WhBattery capacity (Wh): 1024 Wh

Usable energy783 Wh1024 Wh x 85% x 90% x 100% x 100%

Average load165 W500 W running, 165 W average after duty cycle and quantity

Fixed station overheadUnknown (not included)165 W / 85% = 194.1 W battery draw; fixed overhead is unknown and excluded

Estimated runtime4h 45m783 Wh / 165 W = 4h 45m

Assumptions

1024 Wh nominal battery capacity
AC inverter output path
85% conversion efficiency
10% reserve kept unused
165 W average load from 1 load
100% battery health
0% temperature loss
Fixed station overhead unknown; not included

Warnings

This is an estimate. Real runtime changes with load, temperature, battery age, AC/DC output, and device behavior.
The largest startup surge (2900 W) is above the selected station surge rating (2700 W).

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Plan essential power during outages.

Full-size refrigerator worked example

A 1,024 Wh station with 10% reserve and 85% efficiency leaves about 783 Wh before load behavior. Using this page's 500 W default at 33% duty cycle, the planning load is about 165 W and the estimate is 4h 45m.

Change first

Change duty cycle first if the device cycles more or less often than the default.
Check startup surge for motors, compressors, and pumps.
Use measured watts for outage or medical-adjacent planning.

Full-size refrigerator assumptions

Review the Full-size refrigerator scenario page when you need the wattage range, duty cycle, confidence label, and source notes before calculating runtime.

Review Full-size refrigerator scenario

This calculator gives a planning estimate. Treat the result as a starting point, then refine it with measured watts, the device manual, and the station's current output limits.

Verify your watts

Check the device label for running watts or input amps and volts.
Use a plug-in watt meter for AC loads when the result matters.
For cycling loads, measure long enough to capture on/off behavior.

Open wattage library

Check output path

AC inverter loads usually lose more energy than direct DC loads.
Keep reserve for cold weather, battery age, and load changes.
Do not treat label capacity as fully usable watt-hours.

Read the method

Check surge and output

Runtime does not prove a station can start a compressor or motor.
Compare device startup watts with the station surge rating.
Compare running watts with the station continuous output rating.

Check startup surge

Medical-device planning

Use this site as a planning estimate, not medical advice.
Follow the device manufacturer's battery guidance.
Test the full setup before relying on it overnight.

Need a full outage plan?

Use the Emergency Power Plan Builder when you need refrigerator, router, lights, CPAP, phones, Starlink, reserve, solar offset, and model-fit checks in one printable workflow.

Open emergency planner