Residential electric rates at Commonwealth Edison in Illinois are due to rise 40 percent starting June 1, 2014.

ComEd no longer owns power plants and buys power on the open market to serve customers who do not choose an alternative electric supplier.  It periodically updates its Price to Compare -- the electric rate charged for customers who do not choose an alternative supplier.

Starting June 1, 2014, the residential Price to Compare at ComEd will be 7.596 cents per kWh, lasting through September 30, 2014. That's almost 40 percent higher than the current ComEd residential Price to Compare of 5.523 cents per kWh.

The Illinois Commerce Commission has also listed ComEd's residential Price to Compare for the period October 2014 to May 2015 as 7.42 cents per kWh.

These residential Prices to Compare at ComEd apply to both standard customers as well as customers with electric space heating.

The ComEd Price to Compare excludes one charge (or credit) which may appear on a customer's electricity supply bill if they continue to buy power from ComEd -- the Purchased Electricity Adjustment (the PEA).  The PEA is essentially a reconciliation charge, and can vary month to month.

The PEA is typically capped at 0.5 cents per kWh, but its application does mean that the Prices to Compare listed above may vary through the next year.

Customers who shop for a competitive electric supplier avoid (or "bypass") paying ComEd's Price to Compare and also do not pay the PEA