Quick definition
Most electric bills charge for total energy used, measured in kWh. A demand charge is different: it's based on the single highest rate of power draw a business hit at any point during the billing period, measured in kW, usually averaged over a 15-minute window. That one brief peak, even if it lasts only a few minutes, can drive a meaningful chunk of the monthly bill; NREL's own survey of commercial utility tariffs found demand charges often make up 30 to 70% of a commercial customer's total electric bill.
It's separate from, and in addition to, the standard per-kWh energy charge.
At a glance: demand charges are largely a commercial and industrial billing structure and rarely appear on standard residential electric bills.
Why it matters
A demand charge exists because utilities have to build and maintain infrastructure capable of handling a customer's absolute peak draw, even if that peak only happens once a month for a few minutes. A business that runs steady, moderate power use all month but has one brief spike, say several pieces of equipment starting up at the same time, still needs a utility connection sized for that spike, and the demand charge reflects that.
This creates a very different incentive than a standard energy bill. Reducing total energy use helps, but it doesn't directly address the demand charge if the peak spike is still happening. What actually reduces a demand charge is flattening that one specific peak moment, which is exactly the kind of problem battery storage is well suited for: a battery can discharge specifically during the peak window, covering the spike without the utility ever seeing the business draw that much power from the grid.
Solar alone is a less reliable fix here, since a demand peak can occur at any time of day, including early morning or evening when solar production is low or nonexistent. NREL's own modeling of demand charge savings from commercial solar found the median reduction in billing demand from PV alone is only around 7%. A battery, which can respond to a demand spike regardless of sunlight, generally targets this specific cost more directly and predictably than solar production timing alone, worth checking against the solar savings calculator by utility rate if you're weighing solar-only against a combined solar-plus-storage approach.
Where you'll see this
The commercial demand charge calculator works out the actual dollar cost of your business's current demand charge based on your peak usage pattern.
If you're considering battery storage to reduce that cost, the peak demand battery offset calculator estimates how much a specific battery size could shave off your peak demand.
This term comes up on nearly every commercial and industrial electric bill, in utility rate schedules, and any time a business is evaluating whether battery storage makes financial sense beyond just backup power.
Frequently asked
Rarely. Demand charges are mostly a commercial and industrial billing structure. Most residential utility bills are based only on total energy consumption, not peak demand, though this varies somewhat by utility and rate plan.
Only if the peak demand moment happens to occur during strong solar production. Since demand charges are based on one specific peak window, and that peak can occur at any time of day, solar alone doesn't reliably control when the peak happens. A battery, which can discharge on demand regardless of sunlight, is generally more effective at directly targeting demand charges.
It varies widely by utility rate structure and how large the business's peak demand spikes are relative to its typical usage, but demand charges can represent a substantial share of a commercial electric bill, making even a modest reduction in peak demand potentially meaningful.
Usually several pieces of equipment starting up or running at full load at the same time, like HVAC systems, industrial machinery, or EV chargers all drawing power simultaneously during a short window, even if that peak lasts only a few minutes.