Understanding Illinois Utility Tariff Structures: What Rate Class Is Your Business On and Does It Matter?

Most Illinois commercial business owners know what they pay for electricity each month. Far fewer know how that number is calculated — specifically, which utility tariff structure applies to their account and whether that structure is optimal for their usage profile. This gap in knowledge is more costly than it might appear.

The utility tariff structure (or rate schedule) your business is on determines the rules by which every component of your bill is calculated: fixed charges, variable energy rates, demand charge structures, time-of-use pricing, and eligibility for specific programs. Two businesses in the same building, consuming identical amounts of electricity, can have very different bills if they're on different rate schedules — and for some businesses, being on the wrong schedule costs thousands of dollars annually.

This guide explains Illinois's commercial utility tariff structures in practical terms: what the major rate schedules are, how to determine which one applies to your business, what each class costs you, and whether you might be on the wrong rate class for your current operations.

What Are Illinois Utility Tariff Structures and Why Every Business Owner Needs to Understand Them

A utility tariff is a legally filed, ICC-approved document that specifies the terms, rates, and conditions under which ComEd or Ameren Illinois provides electricity service to customers in different categories. Tariffs are not negotiated individually — they're set by the utility, approved by the ICC after public proceedings, and applied uniformly to all customers that qualify under each schedule's criteria.

Commercial electricity tariffs typically differ from each other in several key ways:

Fixed monthly customer charge: A flat fee per month regardless of usage. Larger commercial accounts tend to have higher fixed charges.

Variable energy charge: A per-kWh charge applied to total consumption. May be flat, tiered (price changes above certain thresholds), or time-differentiated (different rates for on-peak and off-peak hours).

Demand charge: A per-kW charge based on your peak demand in the billing period. Some rate schedules include no demand charge (most small commercial accounts); others have complex multi-component demand structures.

Applicable riders: While most riders apply across all rate schedules, some are specific to certain schedule types.

Time-of-use provisions: Whether the rate distinguishes between when during the day, week, or season you use electricity.

Understanding which tariff applies to your account — and whether there's a more favorable alternative for your specific usage profile — is one of the most underutilized cost management levers available to Illinois commercial customers.

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How to Find Out What Rate Class Your Illinois Business Is On — And What It's Costing You

Locating Your Rate Schedule on Your ComEd Bill

Your rate schedule is shown on your ComEd commercial electric bill, typically in the account information section near the top. Look for language like "Rate: BES" or "Rate Schedule: BESH" or similar. If you can't locate it on the bill, log in to your ComEd online account or call the commercial customer service line.

The key ComEd commercial rate schedules are:

BES (Basic Electric Service)

The most common rate schedule for small to medium commercial accounts. BES applies to accounts with annual consumption up to certain thresholds (typically under 15,000 kWh/month for standard BES).

Structure:

• Monthly customer charge (fixed)
• Distribution energy charge per kWh (variable)
• Distribution demand charge per kW (above a threshold demand level)
• Transmission charges (pass-through)
• Capacity charges based on PLC (pass-through)
• Standard ComEd riders

Who benefits: Small businesses with relatively stable, moderate consumption patterns and limited demand management capability.

Caution: For accounts approaching the upper threshold of BES eligibility, verify whether BESH or a larger commercial schedule might be more favorable given your load profile.

BESH (Basic Electric Service High Density Load)

Designed for accounts with higher demand relative to energy consumption — a higher demand-to-energy ratio than standard BES. Applicable to businesses with dense equipment loads relative to their footprint.

Who benefits: Operations with high demand peaks relative to total energy (e.g., welding shops, certain food processing, operations with heavy motor loads).

Caution: The higher demand intensity structure can result in significant demand charges if peak demand isn't managed. Demand management strategies are particularly high-value for BESH accounts.

DS (Default Service)

For larger commercial and industrial accounts transitioning between retail suppliers. DS provides a default supply mechanism for accounts above certain usage thresholds when an ARES supply arrangement is not in place.

Important: DS accounts should be actively shopping the competitive ARES market. These larger accounts represent meaningful volume and typically command the most competitive pricing from ARES suppliers.

TOD (Time of Day)

A voluntary rate schedule offering lower per-kWh prices during off-peak hours (evenings, nights, and weekends) in exchange for higher prices during on-peak hours (typically weekday afternoons and evenings, with summer peak pricing).

Structure: Two-tier pricing with significant differential between on-peak and off-peak rates, plus demand charge components.

Who benefits: Businesses with operational flexibility to shift significant load to off-peak periods — manufacturing operations that can run third shift, businesses that can pre-cool or pre-heat during nights or weekends, accounts with significant overnight or weekend operations.

Who does not benefit: Businesses with fixed operating hours concentrated in on-peak periods, where the higher on-peak rate outweighs any off-peak savings.

Cost comparison example: A business consuming 40,000 kWh/month:

• On BES: 40,000 kWh × $0.04/kWh distribution + demand charges + riders
• On TOD: 20,000 kWh at peak price + 20,000 kWh at off-peak price + demand charges
• Whether TOD saves money depends entirely on the distribution between on-peak and off-peak consumption

RTOU (Real-Time Optimum Use)

An advanced rate schedule tied to ComEd's real-time pricing market. Customers on RTOU pay hourly prices that fluctuate based on the actual wholesale market price. This is ComEd's equivalent of the hourly pricing program available to smaller commercial accounts.

Who benefits: Businesses with sophisticated energy management systems, significant flexibility to respond to price signals, and operations that can curtail or shift load during high-price hours (typically summer peak afternoons and extreme weather events).

Who does not benefit: Businesses without automated response capability, businesses where even brief operational curtailment is costly, and businesses without the administrative bandwidth to monitor hourly pricing signals.

For a detailed analysis of RTOU vs. fixed rates, see ComEd hourly pricing vs fixed: when each wins for small business.

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The Hidden Truth About Illinois Commercial Energy Rate Classes: Are You Overpaying Right Now?

Being on the wrong rate schedule for your current usage profile is a more common and costly problem than most business owners realize. Rate schedule misalignments typically occur in one of three scenarios:

Scenario 1: Business Has Grown, Rate Schedule Hasn't Changed

A business that started small and grew significantly may still be on BES when their consumption and demand profile now qualifies for — and would benefit from — a larger commercial schedule with lower per-unit charges. Utilities don't automatically migrate accounts to more favorable rate schedules; you need to identify and request the change.

Scenario 2: Business Operations Have Changed, Rate Schedule Is Stale

A manufacturer that shifted from single-shift to 24/7 operations dramatically improves their load factor — which might make a TOD schedule advantageous (using the off-peak discount for the new overnight and weekend production). A retailer that moved to extended hours might find their peak demand shifted from on-peak to off-peak in ways that change the economics of TOD vs. flat-rate schedules.

Scenario 3: Efficiency Upgrades Changed the Load Profile

A business that upgraded to LED lighting and high-efficiency HVAC reduced their total consumption — but the proportion of on-peak vs. off-peak consumption may have changed in ways that affect which rate schedule is optimal.

How to Audit Your Rate Schedule Fit

1. Pull 12 months of interval data from ComEd (or via Green Button/Green Button Connect)
2. Calculate your actual on-peak vs. off-peak consumption split for the past year
3. Ask your broker or an energy consultant to model your annual cost under each applicable rate schedule
4. If a different schedule yields lower costs, contact ComEd to initiate a rate schedule change request

Note: Rate schedule changes typically take effect in the next billing period after approval, and utilities may require a minimum period before allowing another change. Confirm the terms of any schedule change before requesting.

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How Switching or Negotiating Your Illinois Utility Rate Class Can Save Your Business Thousands Annually

The potential savings from rate class optimization vary significantly based on your specific situation, but the range is meaningful:

Small manufacturer shifts to TOD: A manufacturer with 30% on-peak and 70% off-peak consumption (due to night and weekend operations) finds that the off-peak discount on 70% of their load more than offsets the on-peak premium on 30%. Annual savings: $8,000–$15,000 depending on consumption level.

Retail store corrects BESH to BES: A small retailer was incorrectly classified as BESH due to a legacy data entry error. The higher demand charge structure under BESH was costing approximately $400/month more than the appropriate BES rate. Upon correction: $4,800/year in immediate savings with no operational change.

Industrial account qualifies for interruptible rate: A manufacturer with interruptible production processes qualifies for ComEd's interruptible rate schedule (IR-1 or similar), receiving a rate discount in exchange for accepting the possibility of curtailment during grid emergencies. Annual savings: $15,000–$30,000 for qualifying accounts.

For a detailed explanation of interruptible rates, see interruptible rate options: are they worth it?.

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Illinois Utility Rate Schedule Summary: Quick Reference for Commercial Businesses

Schedule	Typical Customer	Key Features	Best For
BES	Small commercial	Modest fixed charge, demand above threshold	Small businesses, stable load
BESH	Dense load, smaller footprint	Higher demand intensity structure	Welding, some food service
DS	Large commercial/industrial	Multiple components, transition schedule	Large accounts between suppliers
TOD	Any commercial	On/off peak pricing differential	Flexible load; off-peak heavy usage
RTOU	Sophisticated commercial	Hourly pricing, market-based	Automated demand response capability
IR	Industrial (interruptible)	Discounted rate; curtailment obligation	Operations tolerant of interruption

Note: Specific schedules, eligibility criteria, and rate structures are subject to ICC approval and can change. Always verify current schedule details with ComEd or Ameren Illinois before making changes.

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Conclusion: Your Rate Class Is Not a Permanent Decision

The utility tariff structure your Illinois business is on is not a permanent assignment. It's a starting point that can and should be revisited whenever your business's operational profile changes significantly. The businesses that manage their energy costs most effectively treat rate schedule optimization as a regular part of their energy management program — checking every 2–3 years whether their current tariff still fits their actual usage pattern.

Combined with competitive supply procurement through the ARES market, rate schedule optimization represents one of the two most impactful levers in the delivery-side component of your energy bill — the portion that isn't changed by switching suppliers but can still be meaningfully reduced through the right tariff structure.

illinoiscommercialenergy.com provides rate schedule analysis as part of our comprehensive commercial energy advisory services. We'll analyze your usage data against available ComEd and Ameren rate schedules, identify any optimization opportunities, and manage the change request process if a switch is warranted. Contact us for a free rate schedule review.

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Sources:

• ComEd – Electric Service Tariff (Full Rate Schedule Document)
• Illinois Commerce Commission – Tariff Filing Database
• Ameren Illinois – Commercial Rate Schedules
• U.S. Energy Information Administration – Utility Rate Structure Overview
• ComEd – Business Rate Information and Schedule Guide

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