Energies Media
A 20-kilowatt solar system sitting on a western Chicagoland roof generated so much electricity last spring that the home sent roughly a megawatt-hour of surplus power back to the grid. The owner expected a bill close to zero — or nothing at all.
Instead, the charges kept coming. Ninety dollars one month. Then $129. Then $153.
The meter showed net surplus. The bank account showed net loss. Something wasn’t adding up.
The homeowner installed the 20kW system in western Chicagoland last November, expecting it to dramatically cut monthly electricity costs. For the first few months, results looked promising on paper — the panels were producing, the meter was spinning backward, and the home was consistently finishing each billing cycle as a net generator.
The bills told a different story. Over five months, charges came in at $90, $0, $84, $129, and $153. Three of those months saw the home produce roughly a megawatt-hour more than it consumed — a clear surplus — and still, a bill arrived.
What confused the homeowner most was a specific line item: “Net Metering Credit – Supply.” That number swung wildly, sometimes a credit, other times a charge, with rates ranging from $0.00383 per kilowatt-hour to $0.09177 per kilowatt-hour depending on the month. “All in all, it feels like something is off,” the homeowner wrote in a post to r/solar. They were right — just not in the way most people would guess.
Five months before posting, the homeowner had opted into ComEd’s hourly pricing plan. The idea made sense at the time: if electricity prices fluctuate by the hour, a solar system producing during daylight should capture the best rates and maximize savings.
Solar panels, though, don’t always produce when prices peak. Under hourly pricing, the value of electricity exported to the grid shifts constantly throughout the day. Surplus sent back during low-demand hours earns very little, while power drawn from the grid after sunset costs whatever that particular hour carries — which can run considerably higher.
That timing mismatch is what drives unexpected bills. Even when a home produces more than it uses across an entire month, the gap between when exports happen and when imports happen can leave the math working against you. The net metering credit rate swinging between $0.00383 and $0.09177 per kilowatt-hour reflects exactly that volatility.
Commenters on the original post flagged another factor: ComEd’s capacity charge. This fee isn’t based on how much electricity you use in a given month. It’s calculated using your household’s highest usage day from the previous year — a detail that matters enormously for new solar adopters.
Because this homeowner switched to hourly pricing before completing a full year with the solar system installed, ComEd was still calculating the capacity charge using pre-solar consumption data, when the home was drawing significantly more power from the grid. The result was a fee that reflected old habits rather than the home’s new, lower-demand reality.
“Read up on ComEd’s ‘Capacity Charge’ for hourly pricing,” one commenter advised. “I was told to wait a full year after installing solar to switch to the hourly pricing.” This isn’t an isolated quirk — it’s a structural timing issue that can catch any new solar adopter off guard if they switch rate plans before the utility has a full year of post-installation data.
Across most of the United States, net metering programs run on a simpler principle. Surplus electricity sent to the grid earns credits that roll over month to month, and homeowners who consistently overproduce typically pay little beyond fixed grid-connection fees — usually somewhere between $10 and $40 per month, depending on the utility and state.
ComEd’s hourly pricing plan operates on a fundamentally different model. Rather than a straightforward one-to-one exchange, it credits and charges based on real-time market rates, so the value of exported solar power is never fixed and can fall well below the cost of power imported after dark. The homeowner is still saving money compared to having no panels at all, but the savings are considerably smaller than anticipated. Rate plan selection, it turns out, can be just as consequential as system size.
The homeowner did find one significant upside to the hourly plan: EV charging rebates. Before going electric, they were spending around $800 a month on gasoline for a V8 vehicle used for a nearly 100-mile daily commute. That cost dropped to near zero after switching to an EV and pairing it with the solar system — a compounding benefit that offsets much of the billing frustration.
If you’re navigating something similar, a few things are worth keeping in mind. Review each bill line item separately; supply charges, delivery charges, fixed fees, and net metering credits each tell a different part of the story. Before switching to hourly or time-of-use pricing, ask your installer or utility how that plan interacts with net metering. Waiting a full year after installation before changing rate plans may also allow your capacity charge to reflect actual post-solar usage, potentially lowering costs by a meaningful amount.
The technology worked. The panels produced. The billing structure just hadn’t been set up to match.
Carlos is an engineer with strong expertise in technical and industrial topics. He previously worked at international companies such as Siemens and is multilingual.
Carlos is an engineer with strong expertise in technical and industrial topics. He previously worked at international companies such as Siemens and is multilingual.
Carlos is an engineer with strong expertise in technical and industrial topics. He previously worked at international companies such as Siemens and is multilingual.

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