The average price of electricity in North Carolina is 13.31 cents per kWh. If your system uses 500 watts and you run it 24/7 (which is unlikely), then you will spend $1.60 a day to run the dehumidifier. To see your desired systems' daily energy costs, here's the math.
1) Take your desires systems wattage. and multiply it by the hours used per day.
2) Divide that number by 1000.
3) Multiply it by the kilowatt-hours rate. In North Carolina, the current kWh is 13.31.
4) Move despicable two numbers to the left and that's how much it costs each day to run.