A commercial solar proposal can be a convincing document. The numbers show a dramatic reduction in your electric bill, and the payback period looks reasonable. But when a St. Cloud business owner looks more carefully at that projected savings figure, one question tends to surface: how much of the demand charge is actually going away, and why does the installer seem confident about a number that’s hard to verify?
That question matters more than most proposals let on. Demand charges can represent 30 to 50 percent of a commercial electric bill, and the relationship between solar output and demand savings isn’t what most buyers assume. Getting the answer wrong doesn’t just affect first-year returns. It compounds across the entire useful life of the system.
We’ve been working with commercial electrical systems in St. Cloud since 1944, and our licensed, bonded, and insured team at Erickson Electric Company has seen the gap between projected demand savings and actual bill results play out more than once. What follows is an honest breakdown of how demand charges work under the Xcel Energy rate structure most local businesses are on, and what that means for your solar ROI.
What a Demand Charge Actually Measures on a Commercial Bill
Most commercial electric bills contain two separate line items that get lumped together in casual conversation about “the electric bill.” The energy charge is based on total kilowatt-hours consumed during the month. The demand charge is different. It’s based on the single highest burst of power draw recorded during any 15-minute interval in the billing period, not on how much electricity you used overall.
The logic reflects how utilities actually build and maintain the grid. Xcel Energy, which serves commercial customers in St. Cloud as Northern States Power Company, has to keep generation capacity on standby to cover each customer’s worst-case draw, regardless of whether that peak lasts 15 minutes or 15 hours. The demand charge is how that reserved capacity gets recovered. On Xcel’s General Service rate, which applies to most commercial accounts with monthly demand above 25 kW, billing demand equals the customer’s maximum 15-minute demand for the month. That single interval (even a brief one from HVAC startup or equipment cycling) sets the charge for the entire billing cycle. Accounts that consistently exceed 1,000 kW are moved to mandatory time-of-day service.
Why Solar Doesn’t Automatically Lower the Demand Charge
Here’s where most proposals oversimplify. Solar panels reduce the kilowatt-hours your building draws from the grid, which directly lowers the energy charge. Demand charge savings are a different calculation, and the results are often much smaller than buyers expect.
Research from Lawrence Berkeley National Laboratory and the National Renewable Energy Laboratory quantified the problem directly. For commercial systems sized to offset roughly half of annual load, rooftop solar cuts demand charges by only about 7 percent in the median case under a standard non-coincident demand charge design, where the peak can occur at any time of the month. Fewer than 10 percent of simulated buildings saw demand savings above 15 percent from solar alone.
The reason is straightforward: solar can only reduce a demand spike that happens while the panels are producing power. In Minnesota, cloud cover, evening hours, and the short daylight windows of winter all create opportunities for peaks to land outside of solar production hours. One cloudy afternoon in January, when furnaces and lighting peak together, is enough to set the monthly demand charge at a level solar never touched.
The LBNL and NREL findings also showed a clear pattern by building type. Schools and supermarkets, whose heaviest loads tend to track business hours and daylight, saw the highest median demand savings from solar. Hotels and apartment buildings, whose peaks frequently occur in the late afternoon and evening, saw reductions near zero from solar alone. The same holds for 24-hour operations and facilities with significant overnight loads. Knowing your load profile (the shape of your building’s electricity use across each hour of the day) is the starting point for any honest demand savings estimate.
What Actually Increases Demand Charge Savings
Two things change the math in solar’s favor: a more favorable rate design and battery storage. Xcel also offers a program that addresses the gap directly.
Predefined Peak Window Billing
When a utility ties the demand charge to a defined time window (say, noon to 4pm on weekdays) solar production overlaps with the billing period that sets the charge. The same LBNL and NREL analysis found that under these peak-window designs, solar cuts demand charges by about 19 percent in the median case, with some scenarios reaching 40 percent or more. Xcel’s standard General Service rate is a non-coincident design, meaning the peak can land at any hour of any day, which is why most St. Cloud commercial accounts fall into the harder-to-predict category for demand savings.
Battery Peak Shaving
Battery storage extends demand charge savings to any hour of the day. A properly sized battery system charges during low-demand periods and discharges the moment load begins to ramp toward a spike, shaving the 15-minute peak before it registers on the meter. Solar handles daytime generation; storage handles the peaks that solar can’t reach. Solar-only systems work well for energy charge reduction, but solar-plus-storage is the combination that produces defensible demand charge savings across a wider range of building types.
Xcel’s PV Demand Credit Rider
Xcel Energy offers a program called the PV Demand Credit Rider, available to commercial solar systems larger than 40kW AC interconnected through a single production meter. The rider provides a separate monthly credit tied to peak-hour solar production. Its existence is telling: Xcel designed this program specifically because standard demand billing doesn’t reliably reflect the value solar produces during the hours that matter most for grid capacity. If your planned system qualifies and isn’t on the proposal, it’s worth asking why.
Building Demand Charges into a Realistic Solar ROI Estimate
A credible ROI model treats demand charge savings and energy charge savings as two separate line items, not a single blended percentage. The federal Investment Tax Credit, currently 30 percent of total system cost for qualifying commercial projects, and MACRS accelerated depreciation both apply to the full installed cost regardless of how demand savings shake out. That part of the financial case is solid and calculable from the quote. The demand charge savings line is where the verification work is needed.
Before accepting any demand charge savings figure in a proposal, request your building’s 15-minute interval data (sometimes called Green Button data) from Xcel Energy. This is the actual usage record at the resolution that determines your billing demand each month. With that data, an installer can model which of your historical peaks occurred during solar production hours and which didn’t. A proposal built only on annual kWh totals is offering a demand savings figure without the underlying load data to support it.
What to look for in the interval data review:
- Peak timing relative to sunrise and sunset: How many of your highest 15-minute demand events in the past 12 months occurred during daylight hours?
- Seasonal distribution of peaks: Minnesota’s commercial heating loads from November through February can shift peaks to early morning or evening hours when solar output is minimal.
- Frequency of high-demand events: One event at 7am on a winter morning can set the monthly demand charge regardless of strong solar performance on every other day of the month.
The businesses that get the best return from commercial solar tend to be the ones that go into the project knowing exactly which line items are moving and by how much. Requesting your interval data before finalizing a proposal is a straightforward step that makes the whole financial case more defensible. If you want to review what your load profile suggests about demand savings potential, our team at Erickson Electric Company provides free estimates for commercial solar projects and can be reached at (320) 456-0652.