The rate of interest on such amounts shall be the greater of the unadjusted customer deposit rate or the applicable late payment rate, if any, for the service classification under which the customer was billed. Interest shall be paid from the date when the customer overpayment was made, adjusted for any changes in the deposit rate or late payment rate, and compounded monthly, until the date when the overpayment was refunded.
N.Y. Comp. Codes R. & Regs. Tit. 16 § 634.3