therefore...

24 hours * 0.38 KWH ==> 9.12 KWH/day
9.12 KWH/day * 30 days in a month ==> 273.6 KWH/month

assuming $0.08/KWH
$0.08/KWH * 273.6 KWH/month ==> $21.89 / month

and that is if you are running it full out every day of the month. your mileage may vary