"$ Monthly" is the approximate cost per month you are paying to run the appliance (in U.S. dollars). This is calculated by taking the total cost per year and dividing it by 12 (the number of months in a year).
PLEASE NOTE: If you provide "months/year" usage, "$ Monthly" is calculated by taking the total cost per year and dividing it by the number of months provided. Actual monthly charges will only be assessed on the months that the appliance is in use.