The electrical rating sheet for a typical 25.1 cu. ft. Kenmore side by side refrigerator is provided below. Power usage in watts will vary depending on the components that are running in the refrigerator. The compressor (at 70 degrees ambient) will use 140 watts +/- 20 watts. The evaporator and condenser fans will be running at the same time as the compressor.
During the automatic defrost mode, the defrost heater will be using 550 to 650 watts for about 1/2 hour.
As a standard, refrigerators are rated by kWh per year for energy usage. The refrigerator used in this example is rated at 721 kWh per year.
If you need more information about your particular refrigerator, resubmit your question with the full model number and additional details.
If you need power consumption to size a back up generator, amp draw is usually used instead of wattage consumption.