Ill. Admin. Code tit. 83 § 655.20
"Act" means the Public Utilities Act [220 ILCS 5 ].
"Base period" means the remaining months in the reconciliation year that includes the effective month.
"Billing unit" means the unit of billing for water billed to the customer by the utility, for example, thousands of gallons or hundreds of cubic feet.
"Commercial customer" means any customer that is not a residential customer or multi-unit residential customer.
"Effective month" means any month during which the water/sewage treatment surcharge shall be in effect.
"Equivalent billing units" means the number of 5/8-inch meters equivalent in flow to a larger meter.
"Information sheet" means a tariff sheet supplemental to the rider filed in accordance with this Part that establishes the initial or modified amount of a purchased water/sewage treatment surcharge.
"Large commercial customer" means a commercial customer with an annual water use of 100,000 gallons or more.
"Multi-unit residential customer" means a dwelling unit used primarily as a residence and located in a master metered building containing more than one such dwelling unit.
"Purchased water/sewage treatment surcharge" means the amount added to a customer's bill in accordance with Section 655.40 of this Part.
"Rate zone" means the service areas to which a particular base rate or purchased water/sewage treatment surcharge applies, but does not include areas that have different base rates or purchased water/sewage treatment surcharges, even though such areas may be served by the utility.
"Reconciliation year" means the calendar year for which actual water and sewage costs and revenues attributable to the purchased water/sewage treatment surcharge are to be reconciled.
"Residential customer" means a customer serviced at an individually metered premises used primarily as a residence.
"Small commercial customer" means a commercial customer with an annual water use below 100,000 gallons.
Ill. Admin. Code tit. 83, § 655.20