Hourly supply pricing is one of the few electricity decisions where the correct answer is genuinely different for two businesses on the same street. It pays off for a load shape, not for a business type, a size or an industry, and that is why the advice you find written about it is usually useless.
It is also why the answer for a ComEd account does not transfer to an Ameren Illinois one, in either direction.
What hourly supply pricing actually does
On a fixed supply rate you pay one price per kilowatt hour regardless of when you use it. That price is not free of the market; it contains a premium your supplier charges for absorbing the risk that wholesale prices spike.
On an hourly rate you pay something close to the wholesale price as it moves, hour by hour, and you absorb that risk yourself. You keep the premium and you keep the exposure.
Whether that trade is good depends entirely on when you use electricity relative to when the market is expensive. A business whose load sits overnight and at weekends is buying cheap hours and paying no premium. A business whose load peaks on summer weekday afternoons is buying exactly the hours everyone else wants.
In ComEd territory this is offered to nonresidential customers as Rate BESH, the hourly form of Basic Electric Service, alongside the fixed Rate BES. Both are ComEd's own default supply rather than a third-party supplier product, and the choice between them is a real, reversible tariff election.
Why we will not tell you Ameren Illinois's version
We reconstruct ComEd commercial bills from the interval record behind them and reconcile the result to the cent. We have not reconciled an Ameren Illinois bill.
So we will not name Ameren Illinois's hourly tariff, state whether your class is eligible for it, or quote what it would have cost you. Reading that off a filing and presenting it as an answer would be the exact move this project exists to argue against, and the cost of being wrong falls on you rather than on us.
Your utility representative can tell you whether an hourly supply option is available to your rate class, and the filed rate schedules are public at the Illinois Commerce Commission. Those are the authorities. Ask them directly.
The test that decides it, and it is the same in any territory
This part does transfer, because it is arithmetic on your own data rather than a property of a tariff.
Take twelve months of your interval record. Price it twice. Once at the fixed rate you are actually paying, and once at the hourly prices that actually occurred over the same twelve months. Compare the totals.
That is the whole test. It is a backward-looking measurement rather than a forecast, and its honest limitation is that the next twelve months will not be the last twelve. What it tells you is not "you will save this much." It is whether your shape is structurally on the right side of the trade, and by how large a margin, which is the thing that does persist.
Two things to insist on when anyone runs this for you:
The comparison must use your metered hours, not a profile. A class-average load profile assumes you look like your neighbors, and the entire reason your answer differs from theirs is that you do not.
The worst month must be shown, not just the annual total. Hourly pricing usually wins on the year and loses badly in a handful of summer afternoons. If your operation cannot tolerate the worst month, the annual average is not the number that governs your decision.
What to establish before you elect anything
Three things, in order.
Your load shape at hourly resolution. Not monthly kilowatt hours. The shape is the input, and monthly totals destroy it.
Whether your peak hours are also the market's peak hours. Summer weekday afternoons are where the exposure lives. A business that is closed then is in a different position from one that is running hardest then.
Whether you can move anything at all. Exposure you can respond to is an opportunity. Exposure you cannot respond to is just risk, and risk you cannot manage is worth paying a premium to avoid, which is what the fixed rate is.
If you are in ComEd territory, we can run that comparison against a reconciled bill. If you are on Ameren Illinois, the method is identical and the tariff inputs are the part we would have to establish first, honestly and from your documents rather than from ours.
Does Ameren Illinois offer hourly electricity pricing to businesses?
We have not reconciled an Ameren Illinois bill and will not assert what is available to your rate class. Ask your utility representative, and read the rate schedules filed with the Illinois Commerce Commission, which are public.
What is ComEd's Rate BESH?
The hourly form of ComEd's Basic Electric Service for nonresidential customers, sitting alongside the fixed Rate BES. It passes hourly wholesale prices through instead of charging a fixed per-kilowatt-hour supply rate.
Who does hourly pricing usually suit?
Operations whose consumption sits outside summer weekday afternoons, and operations that can genuinely move load when prices spike. It suits a shape rather than an industry, which is why it has to be tested against your own interval record.
Can I test hourly pricing without switching?
Yes. Price twelve months of your own interval data at both the fixed rate you pay and the hourly prices that actually occurred, then compare. That measures the decision against history rather than against a projection, and it costs you nothing to run.