CUB Calculator FAQs

Why did CUB create this calculator?

Illinois residents have the option of choosing their own electric supplier. Before making a decision, however, it is important to compare potential offers (including rates and monthly fees) to the regulated utility, ComEd or Ameren. The CUB Power Calculator, at, can estimate whether you’ll save more money with an alternative supplier—either on an individual basis or through your community’s aggregation program—or if you should stay with the regulated utility.

What plans can I compare with the calculator?

The CUB Power Calculator allows you the flexibility to input rates from any potential plans you have seen marketed—including community power (municipal aggregation) deals. Simply enter the amount of a plan and any monthly fees and the tool will calculate if you will save money compared to the regulated utility.

How does the calculator work?

The calculator compares the total amount you would pay if you were a ComEd or Ameren supply customer through May of 2016 to what you would pay with another offer.

1) Enter the per-kilowatt-hour (kWh) price (and a monthly fee, if there is one) of an alternative supplier offer.

2) Enter your estimated electricity usage for each month, in kWh. (The calculator assumes power usage of 900 kWh a month, but you can adjust that if you want. Your estimated power usage can be based on last year’s bills, or you can just fill in what you think you might use.)

3) Hit “Calculate.”

The calculator multiplies the estimated electricity usage for each month by the utility’s supply rates as well as the alternative supplier rates to give you a comparison of what you would pay with each option. Once totals are determined, the calculator tells you whether or not you would save or lose money if you stay with the regulated utility.

What if I don't know my exact power usage?

If you do not have your exact power usage for the past year on hand, you can use the estimates the calculator provides for you, 900 kWh each month. Your usage may vary. You can consult your bills to see past usage and then estimate what your usage will be going forward.

What portion of my bill does the calculator cover?

The calculator compares rates for the “supply” portion of your bill—in other words, what you pay for the cost of the electricity, itself. This does not cover the delivery portion of your bill (what it costs to deliver the electricity to your home). The regulated utility, ComEd or Ameren, is always responsible for the delivery side of your bill. Delivery charges are in addition to the supply costs the calculator estimates.

Do the calculator results include exit fees?

Calculator results do not include exit fees. Please consider the cost of any such fees when determining whether or not to switch suppliers.

What is the PEA, and how does it impact ComEd and Ameren’s price?

The “Purchased Electricity Adjustment” (PEA) is a credit or charge that changes on a monthly basis and attempts to reconcile what electric utilities paid for power vs. what they charged consumers. Alternative supplier rates are NOT impacted by a PEA. This only affects the regulated utility’s price. ComEd and Ameren are required by law to pass the price of electricity onto consumers with no markup. If there is any discrepancy (over or under) between what ComEd or Ameren paid for electricity and what you paid for energy, the PEA should account for it.

CUB’s calculator does NOT account for the PEA, because it’s impossible to predict what it will be on a monthly basis.

Can I use the calculator if I am part of my town's municipal aggregation deal?

Yes. Simply enter the amount you are paying through your municipality’s deal and any monthly fees.

What is municipal aggregation?

Illinois law allows municipalities to buy electricity on behalf of residential and small-business utility customers. This is called “municipal aggregation.”

The idea behind municipal aggregation is that local leaders can use the collective buying power of a community’s residents to potentially negotiate lower prices. (It’s similar to Costco buying in bulk to secure lower prices for its customers.) Municipal aggregation was once a sure bet for electricity savings. However, due to changes in the electric market, aggregation no longer guarantees the same savings as before.

For more information, read CUB’s fact sheet on municipal aggregation.

Where can I see a list of alternative electric offers?

CUB publishes a weekly-updated list of offers from alternative electric suppliers. Get the guides for Ameren and ComEd customers emailed to you here.

You can see a list of municipal aggregation (community power) deals here: