Charging during off-peak hours saves the most money on your Illinois electric bill

The best time to charge your EV at home in Illinois depends on your utility company's rate structure. Most Illinois utilities offer time-of-use (TOU) rates that charge less per kilowatt-hour during certain hours — typically late evening through early morning. If your utility does not publish a TOU rate, charging during any off-peak period still costs less than peak hours, though the savings are smaller.

ComEd, which serves northern Illinois including Chicago, charges the lowest rates between 9 p.m. and 6 a.m. on weekdays and all day on weekends and holidays. Ameren Illinois, which covers central and southern Illinois, has different windows depending on your rate plan — some offer off-peak rates from 8 p.m. to 7 a.m. weekdays. Smaller municipal utilities and cooperatives have their own schedules. The first step is to check your utility bill or log into your account online to see what rate structure you are on.

Key Takeaways

  • ComEd's off-peak charging window is 9 p.m. to 6 a.m. on weekdays and all day weekends, with rates roughly 30 to 40 percent lower than peak hours.
  • Ameren Illinois off-peak times vary by rate plan, so you must check your specific bill or account to know your windows.
  • Charging during off-peak hours can save $300 to $600 per year depending on your vehicle's efficiency and local rates.
  • A programmable home charger lets you set charging to start automatically during off-peak hours without manual intervention each night.
  • Weekend charging is always cheaper than weekday peak hours on most Illinois utilities, even if you do not have a TOU rate.

ComEd off-peak hours and rates for Chicago and northern Illinois

ComEd's residential TOU rate is called the Residential Time-of-Use Rate, and it divides the day into peak and off-peak periods. Off-peak hours run from 9 p.m. to 6 a.m. on weekdays (Monday through Friday) and all hours on weekends and holidays. Peak hours are 6 a.m. to 9 p.m. on weekdays. The off-peak rate is typically 30 to 40 percent lower than the peak rate, though the exact cents-per-kilowatt-hour varies by month and season.

ComEd publishes its current rates on its website, and you can view them by logging into your account or calling their customer service line. The rate changes monthly, so the difference between peak and off-peak shifts slightly throughout the year. Winter months often have smaller gaps between peak and off-peak rates, while summer months — when air conditioning drives peak demand — have larger gaps. Charging your EV during the 9 p.m. to 6 a.m. window on a weekday, or anytime on Saturday or Sunday, puts you in the lowest-cost period.

Ameren Illinois off-peak windows and how to find your rate plan

Ameren Illinois serves central and southern Illinois and offers multiple residential rate options. The most common is the Residential Time-of-Use Rate, which typically has off-peak hours from 8 p.m. to 7 a.m. on weekdays and lower rates all day on weekends. However, Ameren also offers a flat rate option with no time-of-use component, and some customers are on older rate plans with different windows. You must check your bill or log into your Ameren account to confirm which rate you are on.

If you are on a flat rate with no time-of-use pricing, Ameren still charges less during lower-demand periods — typically nights and weekends — but the difference is built into a single rate rather than shown as separate peak and off-peak prices. Switching to a TOU rate is usually free and can be done by contacting Ameren directly. Some customers find that a TOU rate saves money only if they can shift most charging to off-peak hours; if your driving pattern requires daytime charging, a flat rate may be simpler and cost about the same.

How much you can save by charging during off-peak hours

The dollar savings depend on three factors: your vehicle's efficiency (measured in kilowatt-hours per mile), how many miles you drive per month, and the difference between your utility's peak and off-peak rates. A typical EV uses about 0.25 to 0.35 kilowatt-hours per mile. If you drive 1,000 miles per month and your off-peak rate is 35 percent cheaper than peak, shifting all charging to off-peak hours could save $30 to $50 per month, or $360 to $600 per year.

The actual savings vary widely. A driver who charges mostly at night and on weekends will see the full benefit. A driver who must charge during peak hours because of work or schedule constraints will see little or no savings. Some households find that the savings from a TOU rate are offset by the cost of installing a programmable charger, though most modern Level 2 chargers include scheduling at no extra cost. Use your current electric bill and your vehicle's efficiency rating to estimate your own savings before deciding whether a rate change makes sense for you.

Setting up automatic charging with a programmable home charger

Most Level 2 home chargers sold today include a scheduling feature that lets you set the charger to start and stop at specific times. You can program the charger to begin charging at 9 p.m. and stop by 6 a.m., or to charge only on weekends, without touching it manually. Some chargers connect to your home Wi-Fi and let you control them from a smartphone app, while others use a straightforward button panel on the charger itself.

When you buy or install a charger, ask the installer or manufacturer whether scheduling is included and how to set it up. Many chargers require you to enter your utility's rate schedule into the charger's settings so it knows when off-peak hours begin and end. If your charger does not have scheduling built in, you can use a smart plug or timer outlet to turn the charger on and off at set times, though this is less convenient and requires you to remember to plug in your vehicle before the timer starts.

Weekends and holidays: always cheaper than weekday peak hours

On ComEd and most Illinois utilities, all-day weekend rates are lower than weekday peak rates, even if you do not have a TOU rate plan. Saturday and Sunday charging is almost always the cheapest option available to you. ComEd treats Sundays and most federal holidays as off-peak all day, so if you can delay charging until the weekend, you will pay the lowest rate your utility offers.

This matters most for drivers who have flexibility in when they charge. If you drive less on weekends and can top up your battery on Saturday or Sunday, you may not need to charge at all during expensive weekday peak hours. Some households with two vehicles find it worthwhile to charge one car on weekday nights and the other on weekends, spreading the load and staying in off-peak windows as much as possible.

Checking your current rate and switching to time-of-use pricing

Your utility bill shows your current rate plan in the summary section, usually near the top. Look for language like "Residential Time-of-Use Rate" or "Residential Flat Rate" or the plan name (ComEd calls theirs "Residential Time-of-Use Rate"; Ameren uses similar naming). If you do not see it on your bill, log into your utility account online or call customer service and ask what rate plan you are on and what the off-peak hours are.

If you are on a flat rate and want to switch to TOU, contact your utility directly — ComEd and Ameren both allow switches online or by phone at no cost. The switch usually takes effect within one or two billing cycles. Before you switch, estimate your savings using your current bill and your vehicle's efficiency. If you charge mostly during peak hours because of your schedule, a TOU rate may not save you money. If you can shift most charging to nights and weekends, the savings often justify the switch within a year.

Frequently Asked Questions

Does charging on a weekend cost the same as charging at 2 a.m. on a weekday?

On ComEd, yes — both are off-peak rates. On Ameren and some other utilities, weekend rates may be slightly different from weekday off-peak rates, so check your specific rate plan. In most cases, the difference is small enough that either option is much cheaper than weekday peak hours.

What if I do not have a programmable charger?

You can plug in your vehicle manually during off-peak hours, or use a smart plug with a timer to turn on a standard charger at a set time. A programmable charger is more convenient but not required to save money — you just have to remember to charge at the right times.

Can I switch back to a flat rate if the time-of-use rate does not save me money?

Yes, switching between rate plans is free and can usually be done online or by phone. If you find that your schedule does not allow off-peak charging, you can switch back to a flat rate at any time.

Do holiday rates explore to all federal holidays?

ComEd treats most federal holidays as off-peak all day, but the list varies slightly by year. Check your utility's holiday schedule on their website or call to confirm which days count as holidays for rate purposes.

Will charging at night wear out my battery faster?

No. Charging speed and time of day do not affect battery wear. Slower charging (which happens at lower power levels) may be slightly gentler on the battery than fast charging, but the time of day makes no difference.