The City of Portland calculates residential single family or multi-family sewer volume using actual water consumption, class average or winter average. The city bases sewer volume charges on actual water usage or an average, whichever is lower.

Actual Water Consumption

The water consumption measured through your water meter.





The water consumption measured through your water meter. Class Average

The average water consumption for a specific account class, such as residential single family or residential multi-family. The city uses class average when there is no water use history or when a winter average is not available.





The average water consumption for a specific account class, such as residential single family or residential multi-family. The city uses class average when there is no water use history or when a winter average is not available. Winter Average

The average water consumption for a specified billing cycle in winter and early spring. Most water used indoors during this time of year enters the sewer system. Since much of the water used in warmer months waters lawns and gardens and doesn’t enter the sewer system, the city uses the winter average as the most equitable way of determining sewer volume. The city applies winter average volume to residential accounts during billing periods outside the winter average review period. During those billing periods, the city bills customers the winter average consumption or actual water consumption, whichever is less.

Winter Average Review Periods

Monthly Billing Cycles

December 1 – April 30





December 1 – April 30 Bi-monthly billing cycles

January 1 – April 30

For residential accounts billed quarterly, the city calculates the winter average on water readings taken between February 1 and April 30.

How to Calculate Your Winter Average

Quarterly Accounts

Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 90.





Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 90. Bi-monthly Accounts

Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 60.





Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 60. Monthly and Budget Billing Accounts

Divide the total winter average review period consumption by the total actual days of service in your review period (days between the billed meter readings in the winter average review period) and multiply by 30.

Winter Average Example

Date Reading Consumption Days between readings

09/17/2017 1026 65ccf* 92

12/16/2017 1052 26ccf 90

03/19/2018 1095 43ccf 94

06/17/2018 1144 49ccf 90

43ccf ÷ 94 days x 90 days = 41ccf

*one ccf equals 100 cubic feet of water

Minimum Use Average

Accounts billed for 0 to 2 ccf during the winter average billing period will be assigned the following winter average based on billing frequency: