If your electricity rate is the average cost in the United States, it is 13 cents per kWh. Running a 1,000-watt food dehydrator for an hour costs 13 cents. A 750-watt one would cost 9.7 cents per hour. A 500-watt food air-dryer costs 6.5 cents per hour, and one that uses 300 watts would be 3.9 cents per hour.