Welcome. My name is XXXXX XXXXX would be glad to assist.Your charger is rated at 1.5 amp input on 120 volts.That equates to 180 watts.So, in order for you to use 1KW (kilowatt), you would run the charger for 5 1/2 hrs.If you get your power bill, you can find what the charge is for 1KWH and multiply that by the number of 5 1/2hr time periods to arrive at the costs.
This is to keep it simple and not try to determine at what point the batteries are almost charged and power needed is less.
Basically a 12hr period is 2 KWH.
My area, the KWH costs are around 11 cents in the summer, 5-6 cents in the winter.So, it would cost me 22 +/- cents a day to charge it 12 hrs.Yours is listed on the electric bill in a separate column as Cost per KWH.Hope that helps, just reply for any clarifications, thanks