1. First, If you have a smart Meter go ComEd online - login and get your historic numbers by day - maybe that is a first start to get a light bulb on in your head?
2. Second, Check your Capacity charge on your bill starting with June Electric usage - July issued - it changes on this bill and it may have has a substantial jump if you got caught 6 or greater time during the Coincidental peak periods in the last year.
3. Third, Check your AC differential air intake and supply temps to makes sure its 19 degrees or greater - if not your AC ran like crazy and you need to get a HVAC service tech out to find the cause. This temperature delta should be checked every year period by you since its such a large cost on the Summer bills.
Hope this helps