Battery capacity and refrigerator consumption are different measurements. To plan off-grid operation, compare the battery's usable energy in watt-hours with the refrigerator's energy use per day, then include other electrical loads and realistic charging conditions.
Step 1: Obtain the exact refrigerator's energy figure
Use the manufacturer's Wh/day or kWh/day rating under documented test conditions. Compressor running watts or maximum amps alone do not tell you how much electricity the fridge consumes per day because compressor duty cycle varies with temperature, loading and operating conditions.
Step 2: Estimate usable battery energy
Usable Wh = rated amp-hours × nominal battery voltage × usable fraction.
Illustrative battery only: 100Ah × 12.8V × 0.80 = 1,024Wh. The 80% usable fraction is an assumption for the example, not a universal discharge recommendation. Use your battery manufacturer's guidance.
Step 3: Estimate idealized runtime
Approximate battery-only days = usable Wh ÷ daily fridge Wh.
Here is a hypothetical example, not the specification for any listed refrigerator:
| Example fridge use | Idealized runtime from 1,024Wh |
|---|---|
| 400 Wh/day | About 2.6 days |
| 600 Wh/day | About 1.7 days |
| 800 Wh/day | About 1.3 days |
These results are not guaranteed: they omit wiring losses, battery behaviour, other 12V appliances, solar variability, fridge cycling and actual weather.
Step 4: Plan solar and charging
- Add refrigerator consumption to lights, fans, furnace controls and other daily DC loads.
- Use location- and season-appropriate estimates of solar production rather than panel nameplate watts alone.
- Allow for shaded or cloudy days, charging losses and battery-reserve requirements.
- Verify wiring, protection and ventilation requirements for the exact replacement refrigerator.
Why not calculate runtime from only the fridge's maximum amp draw?
Many compressor fridges cycle their compressors. The maximum electrical draw and the day's average energy consumption are not equivalent. Use manufacturer daily-use figures when available.
Can I replace a propane absorption fridge with 12V?
Possibly, but installation depends on cabinet opening, manufacturer ventilation, proper DC wiring and electrical-system capacity. See the refrigerator measurement and power-type guide.
Compare refrigerators and installation dimensions
New 12V DC refrigerators · Propane/electric refrigerators · Size cross-reference guide.
Verify parts before ordering
Use the model-label identification guide and OEM parts-list directory to identify your exact part number. For help, send us the model and product identification information.