Refrigerator Backup Power Planning
Estimate refrigerator battery capacity while accounting for cycling, compressor startup, defrost behavior, and measurement uncertainty.
Published · Updated
What to measure
Measure energy at the wall for at least 24 hours under representative room temperature, door-opening, and food-load conditions. Enter that as daily kWh. A refrigerator’s label or running watts alone cannot describe its full-day cycling and defrost use.
Record operating watts separately for continuous-output checking. Compressor startup can be higher and brief; if you do not have documented magnitude and duration, mark startup unknown rather than guessing.
Illustrative scenario
As a workflow example only, enter your own measured daily kWh and select AC. For a 48-hour outage plan the engine doubles a 24-hour energy measurement exactly once. It does not apply another duty factor.
This is not food-safety assurance or guaranteed outage coverage. Ambient conditions and appliance controls can change consumption, so retain margin and monitor temperatures by appropriate means.
Enter the measurement without double counting
Select Measured daily energy and enter kWh for one representative day, even when planning a longer outage. Set the overall plan window to the outage duration. The calculator scales the daily reading to that window; do not also multiply your input by the number of days or apply a duty factor.
If you only know on-cycle watts, use operating watts and an explicitly estimated duty fraction instead. That estimate is less informative than a full energy measurement because it may miss defrost and other operating modes. Do not use the label’s maximum current as though it were a measured daily average.
Keep the supply available between cycles
Include AC-enabled hours for the whole period in which the refrigerator may call for cooling. Turning the compressor off between cycles does not mean the inverter has been switched off. Check the station’s low-load shutoff or AC timeout settings in its manual before relying on unattended cycling.
A combined refrigerator-freezer is one appliance measurement. Adding a second freezer row for the same unit would count its energy twice. A separate chest freezer needs its own row and output checks.
Worked illustration
An illustrative two-day refrigerator plan
Suppose a representative meter reading is 1.2 kWh per day. This 48-hour illustration scales that reading once and leaves AC enabled throughout. It is not a typical refrigerator rating.
- Energy delivered to the devices
- 2,400 Wh
- Estimated nominal battery capacity required
- 3,404 Wh
Assumptions: full starting charge, 10% stopping reserve, 100% capacity factor, 85% AC efficiency, and 90% USB/DC efficiency. AC idle draw is 5 W for 48 hours when an AC load is present. Values are rounded for display.
Operating and startup power are intentionally unestablished in this energy illustration. Check those requirements and the actual connections before choosing equipment.
Build your own plan
The tool starts empty. Add the exact equipment you intend to use, choose the route it will connect through, and replace illustrative values with your measurements. Review Advanced settings before treating the result as a shopping requirement.
Step 2 · Check the requirements
Results
Your plan summary will appear here.
- Add each device and its time in this plan.
- Review the editable assumptions.
- Choose Calculate requirements.
No personalized result is shown until then.
Device
Related reading
Published by Portable Power Calculator. This is specification-based planning information, not a hands-on product test or electrical safety assurance.