The price on ComEd Hourly Pricing can go below zero, and it does so more often than most people expect. In the fourteen months of settled prices we hold for the ComEd zone, June 2025 through July 2026, the hourly price was negative in 441 of 10,228 hours, about 4.3 percent of the time. The lowest hour in the record was minus 31.38 cents per kWh. This page explains why that happens, what ComEd's filed formula does with a negative number, and why it is a curiosity rather than a reason to choose the rate.
Why the wholesale price goes negative
ComEd Hourly Pricing passes through the PJM wholesale price for the ComEd zone, hour by hour. That price is set by the cost of the last unit of power needed to meet demand. In the middle of the night, when demand is at its lowest, the grid is often carrying more wind and nuclear output than it can use. Nuclear plants cannot ramp down cheaply and wind farms earn a production credit for every unit they generate, so both keep running and are willing to pay to stay on. When that happens the clearing price drops below zero: for that hour, the market is paying anyone who will consume.
That is why the negative hours in our record sit where they do. Ranked by count, the most negative hours began at 4 AM (37 of them), 3 AM (36), 2 AM (34) and 5 AM (31). A second, smaller cluster shows up at 2 and 3 PM on mild, sunny spring days, when solar output is high and nobody is running heat or air conditioning. April 2026 had 104 negative hours, January 2026 had 95, and July 2025 had none.
What the filed formula does with a negative price
Rate BESH, the tariff behind Hourly Pricing, defines the Hourly Energy Charge as the PJM real-time price for the ComEd zone, converted to cents per kWh, multiplied by a loss factor and two uncollectible cost factors. Every one of those multipliers is a positive number a little above or below one. The filed formula has no floor at zero. Applied to a negative price, it produces a negative charge for that hour, which means the energy you used in that hour reduces the supply portion of the bill rather than adding to it.
We state that as what the tariff says, not as what a bill shows. We have not yet reconciled a ComEd Hourly Pricing bill that spans a negative hour, and until we have, the sentence "you get paid for using power at 3 AM" stays a reading of the formula rather than a verified bill line. It is also worth keeping the size in view. Half of the 441 negative hours were within about 1.2 cents of zero, and 398 of them were within 5 cents; minus 31 cents is the extreme, not the typical hour.
Why it changes almost nothing about the decision
Four percent of hours sounds like a lot until you look at when they are. Almost all of them fall between 1 AM and 5 AM, when a typical home is drawing its overnight floor, a few hundred watts of refrigerator, router and standby loads. A negative price on 300 watts for an hour is worth a fraction of a cent. The only load that makes those hours matter is one that can be scheduled into them deliberately, which in practice means an electric vehicle, and for a car the relevant fact is that overnight prices are low every night, not that they are occasionally below zero.
What decides Hourly Pricing for a home is the other end of the curve. The same record that holds 441 negative hours also holds a June 2025 hour at 161 cents per kWh and a July 2026 afternoon average of 14.58 cents. The summer afternoons carry the risk, and they also set the capacity charge. Negative overnight hours are the pleasant side of the same volatility. Neither side tells you what your house would have paid; only your own hours priced against both rates do, and that is what is Hourly Pricing worth it works through.
Does ComEd pay you when hourly prices are negative?
The filed Hourly Energy Charge formula has no zero floor, so a negative wholesale price produces a negative charge for that hour, which reduces the supply portion of the bill. We have not reconciled a bill covering a negative hour, so we describe the formula rather than a bill line. The amounts involved are small.
How often are ComEd hourly prices negative?
In the fourteen months we hold, 441 of 10,228 hours, about 4.3 percent. The count varies a lot by month: 104 in April 2026, 95 in January 2026, zero in July and August 2025.
What time of day do negative prices happen?
Mostly 2 to 5 AM, when demand is lowest and wind output is high. A smaller cluster lands around 2 to 3 PM on mild sunny days in spring.
Should I switch to Hourly Pricing because of negative prices?
No. They are too small and too late at night to move a bill on their own. Switch, or do not, on the basis of your own usage priced against both rates across a full year, with the summer afternoons and the capacity charge included.