Average Monthly Billing Alagasco offers a service called Average Monthly Billing (AMB) that spreads your gas costs throughout the year. Here’s how AMB works: Total the bill amounts from the previous 11 billing periods ADD The bill amount for current billing period MULTIPLY BY The number of days in current billing period DIVIDE BY The number of days in the billing period plus 330. (The 330 represents the number of days for the previous 11 billing periods.) For example, the total for 11 billing periods plus the current billing period is $972.00. Multiply $972.00 x 30 days (number of days in current billing period) which is 29160. Divide 29160 by 360 days  (30 days for the current billing period plus 330 days for the previous 11 billing periods) which equals 81.00. The Average Monthly Billing Amount is $81.00 for that billing period. You will receive the greatest benefit with AMB if you stay on the plan year round. To remain on AMB, you must pay the AMB amount in full each month. When AMB is discontinued, any balance on the account is due at that time. Ready to enroll in the Average Monthly Billing Plan?  We make it easy to get started: On the Web: Contact Us to request enrollment in Average Monthly Billing. On the phone: Call 1-800-292-4008  Looking for even more ways to manage your monthly gas payments? Add the convenience of Bank Draft and Ebill for more Alagasco services that are free for customers on the Average Monthly Billing. Frequently asked questions >>