Time-of-Use Rates in Illinois: Optimizing Your Energy Consumption for Savings

The #1 Secret to Slashing Your Illinois Utility Bill: What Are Time-of-Use Rates?

Time-of-use rates represent a fundamental shift in how electricity is priced. Instead of charging a flat rate per kilowatt-hour regardless of when you use it, TOU pricing varies based on the time of day, day of week, and sometimes season. Understanding this pricing structure is the first step toward potentially significant savings.

The Basics of Time-Varying Electricity Prices

Under traditional flat-rate pricing, every kWh costs the same whether you use it at 3 AM or 3 PM. This simplicity ignores a crucial reality: electricity actually costs different amounts to produce and deliver at different times.

During peak demand periods (typically hot summer afternoons when air conditioning loads surge), utilities must:

• Fire up expensive "peaker" power plants that only run during high-demand periods
• Purchase additional power from the wholesale market at premium prices
• Push their transmission and distribution infrastructure to capacity limits
• Risk grid instability that could lead to brownouts or blackouts

During off-peak periods (overnight, early morning, weekends), the situation reverses. Efficient baseload plants produce more than enough power, transmission lines have spare capacity, and wholesale prices drop significantly.

Time-of-use rates reflect these real cost differences, creating a financial incentive for customers to shift usage away from expensive peak periods.

How TOU Rates Are Structured

While specifics vary by utility and rate class, most TOU rate structures include:

Peak period (highest rates): Typically weekday afternoon/evening hours during summer months when system demand is highest. Rates may be 2-5× higher than off-peak.

Shoulder/mid-peak period: Transitional periods between peak and off-peak, often morning hours and early evening. Rates fall between peak and off-peak.

Off-peak period (lowest rates): Overnight hours, early mornings, and often weekends and holidays. Rates may be 30-60% lower than flat-rate pricing.

Super off-peak (some programs): The lowest-cost hours, typically overnight when demand is minimal. Some programs offer extremely low rates during these windows.

Illinois TOU Rate Availability

Both ComEd and Ameren Illinois offer time-varying rate options:

ComEd offerings:

• Hourly pricing for residential customers through the ComEd Hourly Pricing program
• Time-of-use rates for commercial and industrial customers
• Demand response programs that complement TOU pricing

Ameren Illinois offerings:

• Power Smart Pricing for residential hourly rates
• Time-of-use options for commercial customers
• Various rate schedules with time-differentiated components

TOU vs. Real-Time (Hourly) Pricing

It's important to distinguish between TOU rates and real-time pricing:

Time-of-use rates: Fixed rates for pre-defined time periods. You know exactly what each kWh will cost during peak vs. off-peak hours throughout the billing period. Rates are set in advance and don't change day-to-day.

Real-time/hourly pricing: Rates vary hour by hour based on actual wholesale market prices. Each hour's rate is determined by real-time market conditions. More volatile but potentially greater savings for those who can respond to price signals.

TOU rates offer more predictability, while real-time pricing offers potentially greater savings but requires more active management. For most residential customers and many businesses, TOU rates represent a good balance of savings potential and simplicity.

The Behavioral Shift TOU Requires

Success with TOU rates depends on your ability and willingness to change behavior:

• Run major appliances during off-peak hours
• Pre-cool or pre-heat your home before peak periods
• Charge electric vehicles overnight
• Schedule energy-intensive business operations during lower-cost windows
• Reduce or eliminate discretionary usage during peak hours

Not everyone can make these shifts. Night-shift workers who sleep during off-peak hours, businesses that must operate during standard hours, or those with inflexible schedules may find TOU rates increase rather than decrease their bills.

Your 24/7 Playbook: Mastering ComEd & Ameren's Peak vs. Off-Peak Hours for Massive Savings

To optimize under TOU pricing, you need to know exactly when peak and off-peak periods occur. Here's the detailed breakdown for Illinois utilities.

ComEd Time Periods

ComEd's TOU rate structures typically follow these patterns (verify current schedules with your specific rate tariff):

Summer (June - September):

• Peak: Weekdays 1:00 PM - 9:00 PM (highest rates)
• Off-peak: All other hours, including weekends and holidays

Winter (October - May):

• Peak: Weekdays 6:00 AM - 10:00 AM and 5:00 PM - 9:00 PM
• Off-peak: All other hours, including weekends and holidays

Rate differentials: Peak rates may be 30-100% higher than off-peak rates, depending on the specific rate schedule and current pricing.

Ameren Illinois Time Periods

Ameren's TOU structures vary by rate class but generally follow these patterns:

Summer (June - September):

• Peak: Weekdays 10:00 AM - 8:00 PM
• Off-peak: All other hours, weekends, and holidays

Non-summer (October - May):

• Peak: May have reduced peak hours or lower peak/off-peak differential
• Off-peak: Expanded off-peak windows

Understanding Rate Differentials

The savings potential depends on the difference between peak and off-peak rates. Let's illustrate with example numbers:

Note: These are illustrative rates. Actual rates vary by utility, rate class, and current tariff schedules.

Seasonal Considerations

Summer months present both the greatest challenge and the greatest opportunity under TOU pricing:

The summer challenge:

• Air conditioning is essential during peak afternoon hours
• Peak rates are highest during summer months
• Hot afternoons are exactly when you need cooling most

The summer opportunity:

• Rate differentials are largest, maximizing savings from shifted usage
• Pre-cooling strategies can be highly effective
• Many discretionary loads (laundry, dishwashing, EV charging) can easily shift to off-peak

Holiday and Weekend Benefits

Under most TOU rate structures, weekends and holidays are treated as off-peak periods regardless of the time of day. This means:

• Running energy-intensive tasks on Saturday or Sunday always qualifies for lower rates
• Major holidays (New Year's, Memorial Day, July 4th, Labor Day, Thanksgiving, Christmas) are typically off-peak
• Businesses that operate primarily on weekends may see significant savings

Creating Your Personalized Schedule

Based on your utility's TOU structure, create a visual schedule for your household or business:

Green zones (lowest cost - shift usage here):

• Late night: 10 PM - 6 AM
• Weekends: All day Saturday and Sunday
• Holidays: All day on recognized holidays

Yellow zones (moderate cost - use normally if needed):

• Morning: 6 AM - 1 PM weekdays (varies by season)
• Evening: 9 PM - 10 PM weekdays

Red zones (highest cost - minimize usage):

• Afternoon: 1 PM - 9 PM weekdays (summer)
• Morning/evening: 6-10 AM and 5-9 PM weekdays (winter)

Post this schedule visibly and train household members or employees to follow it.

5 Game-Changing Strategies to Shift Energy Use and Dramatically Lower Your Commercial Bill

Knowing when peak periods occur is only half the battle. These practical strategies help you actually shift usage and capture savings.

Strategy 1: Smart Thermostat Pre-Conditioning

HVAC systems typically represent 40-60% of commercial and residential electricity use. Smart pre-conditioning can dramatically reduce peak period consumption:

For cooling (summer):

• Pre-cool your space to 68-70°F before peak hours begin
• Allow temperature to drift up to 76-78°F during peak hours
• Thermal mass of the building maintains comfort even as cooling reduces
• Modern smart thermostats automate this process based on TOU schedules

For heating (winter):

• Pre-heat during off-peak early morning hours
• Reduce setpoint during morning peak (6-10 AM)
• Maintain comfortable temperatures during midday off-peak
• Reduce again during evening peak (5-9 PM)

Recommended equipment: Smart thermostats from Nest, Ecobee, or commercial building automation systems. Many offer specific TOU optimization features and can integrate with utility programs.

Strategy 2: Automated Load Scheduling

Many appliances and equipment can operate on timers or smart controls:

Residential applications:

• Dishwashers: Delay start to run after 10 PM
• Washing machines/dryers: Run overnight or on weekends
• Electric water heaters: Heat water overnight, coast during peak
• Pool pumps: Schedule for early morning or overnight
• EV charging: Program to begin after off-peak starts

Commercial applications:

• Water heating: Large storage tanks can be heated off-peak
• Ice storage for cooling: Make ice overnight, melt for cooling during peak
• Batch processing: Schedule energy-intensive processes for off-peak
• EV fleet charging: Coordinate fleet charging during overnight hours
• Warehouse operations: Shift picking/packing to early morning shifts

Strategy 3: Peak Demand Shaving with Storage

For businesses or homes with significant peak consumption, battery storage offers advanced demand shifting:

How it works:

1. Batteries charge during low-cost off-peak hours
2. During peak periods, discharge batteries to reduce grid purchases
3. Can virtually eliminate peak-period grid consumption with proper sizing
4. Provides backup power benefit as well

Economics of battery storage for TOU optimization:

• More attractive as peak/off-peak rate differential increases
• Commercial customers with high demand charges see best returns
• Federal Investment Tax Credit (30%) improves economics
• Typical payback: 5-10 years depending on rates and usage

Strategy 4: Behavioral and Operational Changes

Sometimes the simplest strategies are most effective:

For businesses:

• Stagger employee start times to spread out morning load
• Shift high-energy processes to earlier in the day before peak begins
• Reduce lighting during peak hours (daylight often sufficient)
• Delay non-essential equipment startup until after peak
• Create "energy patrols" to ensure compliance during peak periods

For households:

• Cook dinner before peak hours or use outdoor grills
• Take showers before peak periods (saves water heating energy)
• Use ceiling fans instead of lowering AC setpoint
• Close blinds during summer afternoon peak to reduce cooling load
• Coordinate household activities to avoid simultaneous high-draw events

Strategy 5: Equipment Efficiency Upgrades

While you're optimizing when you use energy, also consider reducing how much you use:

High-impact upgrades:

• LED lighting: Reduces lighting demand by 60-75%
• High-efficiency HVAC: Modern systems use 30-50% less energy
• Variable frequency drives: Motors only use power needed for current load
• Smart power strips: Eliminate phantom loads from electronics
• Heat pump water heaters: 3-4× more efficient than resistance heating

Even if you can't eliminate peak usage entirely, reducing the amount you use during peak hours multiplies the benefit of TOU pricing.

Creating Your Action Plan

Start with these steps:

1. Audit your usage: Review interval data to understand when you currently use the most energy
2. Identify shiftable loads: List all equipment/appliances that could operate during different hours
3. Set up automation: Install timers or smart controls for identified loads
4. Program thermostats: Configure pre-conditioning schedules aligned with TOU periods
5. Train occupants: Ensure everyone understands the schedule and importance of compliance
6. Monitor results: Track bills monthly to verify savings

The TOU Litmus Test: Is Now the Right Time for Your Illinois Business to Make the Switch?

Time-of-use rates aren't right for everyone. This section helps you evaluate whether TOU pricing will save you money or cost you more.

Who Benefits Most from TOU Rates?

Ideal TOU candidates share these characteristics:

• Flexible schedules: Can shift significant usage to off-peak hours without major disruption
• Low peak-hour usage: Already consume most energy during off-peak periods
• Controllable loads: Have equipment that can be scheduled or automated
• Energy-conscious culture: Household or business committed to behavioral changes
• Automation capability: Have or willing to invest in smart controls

Businesses well-suited for TOU:

• Manufacturing operations with shift flexibility
• Warehouses and distribution centers with overnight processing capability
• Retailers with morning stocking schedules
• Data centers that can shift workloads
• Facilities with thermal or battery storage

Who Should Avoid TOU Rates?

TOU may increase costs for those who:

• Cannot shift usage: Operations that must run during peak hours
• Have inflexible cooling needs: Data centers, server rooms, or processes requiring constant temperature
• Operate primarily during peak hours: Retail stores, offices, or restaurants with afternoon/evening focus
• Have medical equipment needs: Cannot risk delayed operation for health reasons
• Lack automation capability: Cannot invest in controls to enable shifting

Calculating Your Potential Savings

Before switching, model your costs under both rate structures:

Step 1: Gather interval data

Request 12 months of hourly or 15-minute interval data from your utility. This shows exactly when you consume electricity.

Step 2: Categorize usage by TOU period

Sort your consumption into peak, shoulder, and off-peak hours based on the TOU schedule you're considering.

Step 3: Calculate costs under both scenarios

• Flat rate cost: Total kWh × flat rate
• TOU cost: (Peak kWh × peak rate) + (Off-peak kWh × off-peak rate)

Step 4: Model with shifting

Estimate how much usage you can realistically shift from peak to off-peak, then recalculate TOU costs.

Example calculation:

• Monthly usage: 5,000 kWh (2,000 peak, 3,000 off-peak currently)
• Flat rate cost: 5,000 × $0.10 = $500
• TOU cost (no shifting): (2,000 × $0.15) + (3,000 × $0.06) = $300 + $180 = $480 (4% savings)
• TOU cost (shift 500 kWh): (1,500 × $0.15) + (3,500 × $0.06) = $225 + $210 = $435 (13% savings)

Risk Factors to Consider

Rate changes: TOU rates can change, potentially narrowing or eliminating the peak/off-peak differential that made switching attractive.

Behavioral drift: Initial enthusiasm for load shifting often fades over time. Model savings conservatively.

Unexpected peak usage: A broken AC that runs constantly, or unexpected operational needs, can spike peak usage and costs.

Comfort trade-offs: Aggressive pre-cooling or heating may affect occupant comfort. Ensure strategies are sustainable.

Making the Switch

If analysis indicates TOU will save money:

1. Contact your utility: Request enrollment in TOU rate schedule
2. Install necessary metering: May require smart meter upgrade (typically free)
3. Set up monitoring: Use utility portal to track hourly usage and costs
4. Implement automation: Install timers and smart controls before switching
5. Communicate changes: Ensure everyone affected understands new schedule
6. Review regularly: Check bills monthly initially to verify savings match projections

Most utilities allow switching back to flat rates if TOU doesn't work out, though there may be waiting periods or limitations. Ask about flexibility before committing.

For help analyzing your Illinois electricity options, explore our pricing comparison tools or review hourly pricing program options.

Frequently Asked Questions

Conclusion: Making Time-of-Use Rates Work for You

Time-of-use electricity rates offer Illinois businesses and homeowners a powerful opportunity to reduce energy costs—if they're willing to change how and when they use electricity. By shifting consumption from expensive peak periods to lower-cost off-peak hours, savvy energy users can achieve significant savings without reducing their overall comfort or productivity.

The key to success with TOU rates is honest self-assessment. Before switching, carefully analyze your current usage patterns, identify which loads can realistically be shifted, and calculate projected savings based on actual rate differentials. Not everyone will benefit—if your usage is concentrated during peak hours and can't be moved, flat rates may remain the better choice.

For those who do switch, success requires ongoing commitment. Invest in automation to make load shifting seamless, train household members or employees on new behaviors, and monitor your bills to ensure projected savings materialize. Smart thermostats, timer-controlled appliances, and energy management systems can reduce the effort required to maintain TOU-optimized consumption patterns.

As Illinois continues its clean energy transition under CEJA, time-varying rates are likely to become more prevalent and potentially more advantageous. Grid operators need flexible demand to accommodate increasing renewable energy, and TOU pricing rewards customers who provide that flexibility. Getting comfortable with time-varying rates now positions you well for the future energy landscape.

Whether you're managing a large commercial facility or a single-family home, understanding time-of-use rates empowers you to make informed decisions about your electricity costs. Use the strategies in this guide to evaluate your options and, if appropriate, capture the savings that time-varying rates can deliver.