Glossary of Terms
The words that show up on your bill and in supplier contracts, explained plainly.
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BILLING BASICS
Supply Charge
The cost of the actual electricity you use, set by your supplier. This is the portion that changes when you sign a new contract.
Delivery (Distribution) Charges
What it costs your utility to maintain the poles, wires, and equipment that deliver power to you. Rate-class based and non-negotiable.
Customer Charge
Covers a utility's basic cost of doing business with you: billing, postage, and administration.
Estimated Usage
A bill based on a prior period's usage (adjusted for weather) rather than an actual meter reading, used when a meter wasn't read that month.
Rollover Rate
The default supply rate you're moved to automatically if your contract expires without a new agreement in place — typically higher than a negotiated rate.
MARKET & GRID
MISO (Midcontinent Independent System Operator)
The regional grid operator that manages the wholesale power market for Ameren Illinois territory.
PJM Interconnection
The regional grid operator serving ComEd territory in northern Illinois.
Net Metering
Credits solar-equipped customers receive for power they generate and send back to the grid.
USAGE & DEMAND
kW (Kilowatt)
A measure of demand: how much power you're using at a given moment.
kWh (Kilowatt-hour)
A measure of consumption: the total energy used over a period of time.
Peak Demand / Demand Charge
The highest amount of electricity you draw at any one time, usually the biggest factor in your capacity costs for the year.
Peak Load Contribution (PLC)
A number assigned to your account based on your usage during system peak hours; it directly determines your capacity charges for the following year.
Demand Management
Reducing or shifting electricity usage during peak periods — through load shifting or efficiency upgrades — to lower both usage and capacity costs.
RATES & CHARGES
Capacity (or Capacity Charge)
The cost to reserve enough generation to meet your peak demand, passed through from MISO or PJM. Can change significantly year to year.
Transmission Charge
Covers the cost of moving high-voltage electricity from power plants to local substations.
Ancillary Services Charge
Charges for grid support functions like balancing supply and demand in real time. Small individually, but adds up across accounts.
Line Loss
An adjustment for electricity lost during transmission and distribution, which increases your billed usage slightly beyond what your meter shows.
Renewable Portfolio Standard (RPS) Charge
Funds Illinois' progress toward its clean energy goals. State-mandated and unavoidable.
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