An equal monthly payment plan based on the estimated cost of average annual utility usage minus annual MEAP benefits payable to the utility shall be used as the basis to determine appropriate payments for participation in the Utility Service Protection Program. Monthly payments shall be calculated as follows: The utility shall calculate average annual cost based on a 12-month history of the customer's dwelling or a comparable dwelling; The average annual cost shall be reduced by the amount of the participant's MEAP benefit; and The estimated annual cost shall be divided by 12 to give the monthly payment obligation. The monthly bill shall separately state each of the following: The combined amount due under the equal monthly payment plan plus the amount due under the supplemental payment plan under COMAR 20.31.04.01, if applicable; The actual usage for the month; and The cost of the actual usage for the month. The estimated annual obligation shall be recalculated at least once a year to reflect actual customer consumption. If actual usage exceeds the average monthly billing, the excess may be amortized over future monthly payments.