Auditing a chain of medical offices in Chicago. They buy supply from a competitive supplier and delivery from ComEd. The supply contract says $0.0610/kWh fixed for 24 months. But the supply charges on the bills show varying amounts each month — $0.0610 some months, $0.0645 others, $0.0672 once. The rate isn't fixed. What's going on?
Illinois — supply charges don't match the contract rate
Check the contract fine print for a "pass-through" clause. Some Illinois REP contracts that advertise a "fixed rate" actually have a fixed energy component plus variable pass-throughs for capacity charges, transmission charges, or renewable energy credits. The contract might say $0.0610 fixed but then add "plus applicable capacity and transmission charges" in a separate section. Those pass-throughs cause the monthly rate to vary even though the base energy rate is fixed.
Yuri is right — the "fixed rate plus pass-throughs" structure is very common in Illinois and it's misleading. The client thinks they're on a fixed rate but they're really on a hybrid. Pull the contract and read every section, not just the rate summary page. If the contract does include pass-throughs, verify that the pass-through charges on each bill match the actual ICC-filed rates for those components. Even legitimate pass-throughs can be calculated incorrectly. I've found REPs that pass through transmission charges at rates higher than what ComEd files with the ICC.
Same issue in downstate Illinois with Ameren. The "fixed" rate had three variable pass-through components buried in the contract appendix. My client was paying 8% more than they expected. Switched REPs at renewal and insisted on a true all-in fixed rate with no pass-throughs. Those exist — you just have to ask specifically.
Found the pass-through clause. The contract says "$0.0610 plus applicable PJM capacity and transmission costs." Those costs vary monthly. The contract is technically correct but the sales rep never mentioned the pass-throughs. No billing error per se, but I'm helping the client shop for a true fixed rate at renewal. Thanks everyone.