OUTAGE ATLAS / FIELD NOTES
Refrigerator Battery Backup: How Much Capacity?
For a refrigerator labelled 500 kWh/year, a 12-hour outage needs about 980 Wh of battery capacity under the example assumptions below. Use your own energy label and outage length. Battery capacity alone cannot confirm that the compressor will start.
Opens the existing planner with one editable refrigerator example. The 500 kWh/year and 150 running watts are assumptions, not measurements of your appliance. Startup watts stay unknown.
Start with the yellow energy label
Find the annual electricity use in kWh/year on your refrigerator’s EnergyGuide label. That figure already includes the compressor switching on and off. Do not apply a second “use percentage” to it.
500 kWh/year × 1,000 ÷ 8,760 = 57.1 W average 57.1 W × 12 hours ≈ 685 Wh used by the refrigerator
A hot room, frequent door openings and defrost cycles can change actual use. A suitable energy meter, used according to its instructions over representative days, can provide a better starting point than an annual average.
Allow for the battery’s own losses
The example uses 90% conversion efficiency, 10 W of inverter idle draw and a 10% battery reserve. With those assumptions, the 685 Wh appliance demand becomes about 980 Wh of nominal battery capacity. These are editable assumptions, not specifications for a particular power station.
In the planner, change the outage hours and edit the refrigerator. Choose “EnergyGuide annual kWh,” enter your label’s figure, and enter reliable running watts separately. Add other appliances only if you also need to power them.
Check whether the refrigerator can start
The example’s 150 running watts is a placeholder. Annual energy use does not reveal running or startup watts. Leave startup blank until you have a reliable figure; the planner will keep showing “Needs checking.” Check the exact appliance and battery documentation for motor loads, surge duration, voltage and outlet compatibility.
A larger battery can store enough energy and still fail to start a compressor. Watts and watt-hours answer different questions; the calculation notes explain how we keep those checks separate.
What this estimate cannot tell you
This is an electrical energy estimate. It does not establish food safety, safe storage temperatures or an acceptable outage duration.
Energy-use background: Virginia Cooperative Extension: estimating appliance energy use. The figures here are original worked examples, not measured product tests.