Seasonal work, summer hours, school and other needs take precedence over what a family spends money on, on a month-to-month basis. Pay-as-you-go electricity is common in some western countries and it is not unusual for there to be days where the family cannot afford to top-up until pay-day again, where food etc comes first as a primary need.
I think this would be much better as a rent-to-own program with a flat monthly fee.