Terms & Definitions

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Electric Delivery


Customer Charge - Recovers costs of providing electric service that occur even if no electricity is used in the billing period. Included in the charge are billing, customer support and other supplemental charges.


Distribution Delivery Charge Summer/Non-Summer - Recovers the costs of infrastructure, maintenance and services incurred by the utility to deliver electricity to customers through the distribution system. Summer electric rates are effective June 1 - September 30. Non-Summer electric rates are effective October 1 - May 31.


DS-1 Residential Delivery Service - This electric rate classification is for separately metered, single family living units.


DS- 2 Small General Delivery Service - This electric rate classification is for small general non-residential customers with a monthly demand less than 150 kilowatts (kW) in 11 of the 12 monthly billing periods in the previous calendar year.


Electric Delivery - As a delivery company, Ameren Illinois is responsible for the transmission and distribution infrastructure that moves electricity from the wholesale grid to your door. Delivery service charges allow us to fund, maintain and improve the system that serves you and to respond around the clock to restore service when it is interrupted. Ameren Illinois assigns electric customers to a Delivery Service (DS) rate classification.


Kilowatt (kW) - This is a measure of the rate at which electrical energy is used. Kilo means 1000, so a kilowatt is equal to 1000 watts. The watt was named after Scottish inventor, James Watt. Most common household appliances that use electricity will indicate the wattage that appliance uses at any given point in time. Similar to the speedometer on a car that measures how fast the car is traveling at a given point in time.


Kilowatt-Hour (kWh) - This is a measure of the amount of electricity used over one hour. It would be similar to the odometer on a car that tells how many miles the car has traveled, however the kWh is measuring usage over a specific time frame of one hour. For example, if an electric heater was rated at 1500 watts and it was turned on high for one hour, it would use 1.5 kWh for that hour. If it ran for more than one hour, you would simply multiply 1.5 by the number of hours it was on.


Meter Charge - Recovers the basic costs of providing electric metering services if they are provided by the utility.



Electric Supply


Basic Generation Service (Rider BGS) - The default option that represents the wholesale price paid by Ameren Illinois. Electricity required to meet the needs of the utility's residential and small commercial customers who purchase their electric supply through BGS is acquired through a process conducted by the Illinois Power Agency, an arm of the State of Illinois. BGS charges represent a dollar-for-dollar pass-through of the purchase costs of the electric supply with no markup.


Electric Supply - While delivery service represents the wires and service that bring electricity from its source to you, electric supply refers to the power and energy supplied from the wholesale markets. In Illinois, you have the option to choose the company that provides your electric supply. Ameren Illinois can continue to provide your power through its Basic Generation Service or Real-Time Pricing rates, or you can choose an alternate Retail Electric Supplier. 


Power Smart Pricing (Rider PSP) - Optional residential electric supply service offered from Ameren Illinois. The cost of electricity is priced on an hourly basis with enhanced customer tools and communications.


Purchased Electric Summer/Non-Summer - Recovers the cost of electricity the utility purchases from suppliers and delivers to customers. The utility receives no profit from this charge. Summer electric rates are effective June 1 - September 30.  Non-summer electric rates are effective October 1 - May 31.


Purchased Electricity Adjustment - Allows the utility to match electric power and energy costs with electric power and energy revenue.


Retail Electric Supplier (RES) - A Third-Party alternative retail electric supplier. If you receive your electric supply from a RES, the supplier's name, website, phone number and messages can be seen on the utility's bill.  Please refer questions relating to Electric Supply charges to your supplier.


Real Time Pricing (Rider RTP) - An hourly pricing option for residential and small non-residential customers with a basic level of customer service/support.


Supply Cost Adjustment (Rider PER) - Base cost associated with electric power and energy used by Basic Generation Service (BGS) customers. This rider is also used to apply charges incurred by the utility to bring in electric power energy for customers served under Real Time Pricing (Rider RTP) and Power Smart Pricing (Rider PSP).


Transmission Service Charge - Recovers costs associated with electric transmission service.



Taxes and Other Fees


Clean Energy Assistance Charge - Recovers costs associated with the purchase of zero carbon energy supply.

EDT Cost Recovery - Allows the utility to recover the cost of an electric distribution tax imposed on the utility under the Public Utilities Revenue Act.


Electric Environmental Adjustment (Rider EEA) - Recovers costs incurred by the utility for environmental clean-up of former gas manufacturing sites.


Illinois State Electricity Excise Tax - State tax on electricity usage.


Municipal Tax - Tax imposed by a local municipality that the utility is required to collect.


Renewable Energy Adjustment - Recovers costs associated with the purchase of renewable energy resources.

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Gas Delivery


Customer Charge - Recovers costs of providing natural gas service that occur even if no gas is used in the billing period. Included in the charge are billing, customer support, basic metering and other supplemental charges.


Distribution Delivery Charge - Recovers the costs of infrastructure, maintenance and services incurred by the utility to deliver gas to customers through the distribution system.


Gas Delivery - As a delivery company, Ameren Illinois is responsible for the transmission and distribution infrastructure that moves natural gas from the wholesale grid to your door.  Delivery service charges allow us to construct, maintain and improve the system that serves you and to respond around the clock to restore service when it is interrupted.  Ameren Illinois assigns gas customers to a Gas Delivery Service (GDS) rate classification as defined below.


GDS-1 Residential Gas Delivery Service - This gas rate classification is for separately metered, single family living units. 


GDS-2 Small General Gas Delivery Service - This gas rate classification is for small general non-residential customers whose highest Average Daily Usage is less than 200 therms per day during the 12 monthly billing periods ending each December.


Qualifying Infrastructure Plant Surcharge (Rider QIP) - Recovers costs incurred by the utility for certain natural gas infrastructure improvements. When applicable, Surcharge is abbreviated as “Surchg" on the bill.


Therm - The basic unit for measuring natural gas consumption. Since natural gas meters measure volume and not energy content, a therm factor is used by utilities to convert the volume of gas used to its heat equivalent to calculate the actual energy use. One therm is equal to approximately 100,000 BTUs (British Thermal Unit). Gas furnaces and water heaters typically are rated based on the number of BTUs they are able to burn in one hour. 


Volume Balancing Adjustment - An adjustment made to bills April through December to balance actual delivery service revenues with approved annual revenue levels based on predicted normal weather.



Gas Supply


Gas Supply - While delivery service represents the pipes and services that bring natural gas from its source to you, gas supply refers to the natural gas supplied from the wholesale markets.  Ameren Illinois provides natural gas to residential customers through its System Gas Service (Rider S). Ameren Illinois non-residential customers have the option to choose Ameren Illinois or another gas supplier to provide their natural gas supply. 


Purchased Gas Adjustment Charge (Rider PGA) - Recovers the cost of natural gas that the utility purchases from suppliers and delivers to the customer. The utility receives no profit from this charge.



Taxes and Other Fees


Gas Energy Efficiency Cost Recovery (Rider GER) - Recovers costs, fees, and charges for energy efficiency programs to help customers use natural gas more efficiently.

Gas Environmental Adjustment (Rider GEA) or Recovery of Coal Tar Costs (Rider TAR) - Recovers costs incurred by the utility for environmental clean-up of former gas manufacturing sites.

Illinois State Commerce Commission Tax - State tax on natural gas usage; proceeds are used to support operations of the state agency charged with regulating the utility.


Illinois State Gas Revenue Tax - State tax on natural gas usage.


Municipal Gross Revenue - Tax imposed by a local municipality that the utility is required to collect.



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Lighting Delivery


Customer Charge - Recovers costs of providing electric service that occur even if no electricity is used in the billing period. Included in the charge are billing, customer support and other supplemental charges.


Distribution Delivery Charge - Recovers the costs of infrastructure, maintenance and services incurred by the utility to deliver electricity to customers through the distribution system. 


DS-5 Lighting Service - This electric rate classification is for customers requesting optional outdoor Protective Lighting service at their property.


Electric Delivery - As a delivery company, Ameren Illinois is responsible for the transmission and distribution infrastructure that moves electricity from the wholesale grid to your door. Delivery service charges allow us to construct, maintain and improve the system that serves you and to respond around the clock to restore service when it is interrupted. Ameren Illinois assigns electric customers to a Delivery Service (DS) rate classification.


Kilowatt-Hour (kWh) - This is a measure of the amount of electricity used over one hour. It would be similar to the odometer on a car that tells how many miles the car has traveled, however the kWh is measuring usage over a specific timeframe of one hour. For example, if an electric heater was rated at 1500 watts and it was turned on high for one hour, it would use 1.5 kWh for that hour. If it ran for more than one hour, you would simply multiply 1.5 by the number of hours it was on.


Optional Lighting Charge - Recovers costs of providing Optional Outdoor Protective Lighting service for a specific location.



Lighting Supply


Basic Generation Service (Rider BGS) - The default option that represents the wholesale price paid by Ameren Illinois. Electricity required to meet the needs of the utility's residential and small commercial customers who purchase their electric supply through BGS is acquired through a process conducted by the Illinois Power Agency, an arm of the State of Illinois. BGS charges represent a dollar-for-dollar pass-through of the purchase costs of the electric supply with no markup.


Electric Supply - While delivery service represents the wires and service that bring electricity from its source to you, electric supply refers to the power and energy supplied from the wholesale markets. In Illinois, you have the option to choose the company that provides your electric supply. Ameren Illinois can continue to provide your power through its Basic Generation Service or Real-Time Pricing rates, or you can choose an alternate Retail Electric Supplier. 


Purchased Electric Summer/Non-Summer - Recovers the cost of electricity the utility purchases from suppliers and delivers to customers. The utility receives no profit from this charge. Summer electric rates are effective June 1 - September 30.  Non-summer electric rates are effective October 1 - May 31.


Purchased Electricity Adjustment - Allows the utility to match electric power and energy costs with electric power and energy revenue.


Retail Electric Supplier (RES) - A Third-Party alternative retail electric supplier. If you receive your electric supply from a RES, the supplier's name, website, phone number and messages can be seen on the utility's bill.  Please refer questions relating to Electric Supply charges to your supplier.


Supply Cost Adjustment (Rider PER) - Base cost associated with electric power and energy used by Basic Generation Service (BGS) customers.


Transmission Service Charge - Recovers costs associated with electric transmission service.



Taxes and Other Fees


Clean Energy Assistance Charge - Recovers costs required to support the purchase of zero carbon energy supply.

Electric Environmental Adjustment (Rider EEA) - Recovers costs incurred by the utility for environmental clean-up of former gas manufacturing sites.

EDT Cost Recovery - Allows the utility to recover the cost of an electric distribution tax imposed on the utility under the Public Utilities Revenue Act.


Illinois State Electricity Excise Tax - State tax on electricity usage.


Municipal Tax - Tax imposed by a local municipality that the utility is required to collect.


Renewable Energy Adjustment - Recovers costs associated with the purchase of renewable energy resources. 



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