// Hardware Guide
Understanding Demand Charges and Utility Rate Design for Fleet Charging
We wrote this for whoever owns the electricity bill, not an electrical engineer. It surfaces the questions worth asking your utility and your charging hardware provider — it's not a substitute for a utility-specific rate analysis.
Executive Summary
Fleet operators who plan charging around energy cost alone — dollars per kilowatt-hour — are often surprised by their actual electricity bill, because for most commercial and industrial customers, demand charges based on peak power draw make up a substantial share of the cost, sometimes more than the energy itself. This guide explains how demand charges work, why fleet charging patterns are particularly prone to triggering them, and what levers — charging schedule, hardware selection, and rate structure — a fleet operator has to manage the cost.
Two Different Charges on the Same Bill
Most commercial and industrial electricity bills combine two distinct charges: an energy charge, billed per kilowatt-hour consumed, and a demand charge, billed based on the highest rate of power draw (measured in kilowatts) reached during a billing period, regardless of how long that peak lasted or how much total energy was used. A facility that draws a brief but very high spike in power can face a demand charge disproportionate to its actual energy consumption for the month.
This structure exists because utilities have to build and maintain infrastructure capable of serving a customer's peak demand, even if that peak only occurs for a few minutes a month — the demand charge is effectively a charge for reserving that capacity. For a fleet operator used to thinking about cost in terms of gallons of fuel or kilowatt-hours of energy, the demand charge is often the least intuitive and most underestimated part of the bill.
Why Fleet Charging Is Prone to High Demand Charges
Simultaneous Charging Creates Peaks
If a depot charges several vehicles at the same time — for example, an entire shift's worth of vehicles plugging in at once at the end of the day — the combined power draw can spike sharply for the duration of that overlap, even if the total energy used over the full night is well within the site's average capacity. That spike, not the average, is what the demand charge is measured against.
Fast Charging Compounds the Effect
Higher-power charging equipment delivers more energy faster, which is operationally useful for short charging windows, but it also draws more peak power per vehicle. A depot that adopts faster chargers to solve a charging-window problem can inadvertently increase its demand charge exposure if the faster charging isn't paired with scheduling that spreads the load.
Demand Charges Persist Even After the Peak Passes
In many utility rate structures, a single demand spike can affect the bill for the entire billing period, and in some cases can influence billing for months afterward through mechanisms like a "ratchet" clause, where a high peak sets a minimum demand charge for a following period even if actual demand drops. This means a single poorly timed charging event can have a cost impact well beyond the day it occurred — worth understanding your specific utility's rate structure on this point directly, since it varies significantly by utility and jurisdiction.
Levers a Fleet Operator Actually Has
Staggered Charging Schedules
The most direct lever is spreading vehicle charging start times across the available charging window rather than plugging in the entire fleet at once. Charging management software that sequences or staggers vehicle charging — rather than allowing every vehicle to draw maximum power simultaneously — can substantially reduce peak demand without changing total energy consumed or extending the charging window meaningfully, since the goal is to smooth the load curve, not reduce total charging time.
Load Management and Charger-Level Power Sharing
Some charging hardware and management systems can dynamically allocate available power across multiple vehicles charging at once, capping total site draw at a set threshold and distributing available power among vehicles based on need and charge status, rather than letting each charger draw independently at full rated power. This is a hardware and software capability worth specifying for explicitly if demand charge exposure is a concern, rather than assuming any charging management system handles this by default.
Right-Sizing Charger Power to Actual Need
Faster charging isn't free from a demand-charge perspective — if the charging window is long enough to fully charge vehicles at a lower power level, specifying lower-power chargers can reduce peak demand exposure without sacrificing the ability to fully charge the fleet in the time available. This is a case where matching charger specification to the actual duty cycle and available charging window, rather than defaulting to the fastest available hardware, has a direct cost benefit.
Shifting Charging to Off-Peak Windows
Many utility rate structures include time-of-use components in addition to demand charges, with lower energy rates during off-peak hours. Scheduling charging to align with off-peak windows — where operationally feasible given route schedules — can reduce both the energy charge and, depending on how the utility measures demand, potentially the demand charge as well. The specifics depend heavily on the utility's rate structure, which is worth reviewing directly rather than assuming a generic off-peak pattern applies.
On-Site Battery Storage as a Peak-Shaving Tool
Stationary battery storage at the depot can charge during low-demand periods and discharge to supplement grid power during vehicle charging peaks, reducing the facility's peak draw from the utility even though total vehicle charging demand hasn't changed. This adds a capital cost, so it's worth evaluating against the actual demand charge savings for your specific rate structure rather than assuming it pays for itself in general.
Questions to Ask Your Utility
Ask directly what rate schedule applies to your facility and whether alternative rate schedules exist that might be more favorable for a fleet charging load profile — many utilities offer multiple commercial and industrial rate options, and the default assigned to a facility isn't always the most favorable available. Ask how demand is measured (instantaneous peak versus an averaging window, commonly 15 or 30 minutes) since the measurement method affects how much a brief spike actually costs. Ask whether a ratchet clause applies, and if so, how it's structured and how long a peak affects subsequent billing. And ask what make-ready programs, managed charging incentives, or demand charge mitigation programs the utility currently offers for fleet electrification customers — these change over time and vary significantly by utility, so get current information directly rather than relying on general industry information.
Questions to Ask Your Charging Hardware and Software Provider
Ask whether the charging management system supports load management or staggered charging, and whether that capability is included by default or requires separate configuration. Ask what visibility the system provides into actual demand patterns — a fleet that can see its own demand curve is in a much better position to manage it than one that only sees the metric after it shows up on the utility bill weeks later. And ask whether the charging hardware and software can be configured to cap site-wide demand at a specific threshold, which is the most direct control available against demand charge exposure.
The Practical Takeaway
Demand charges are a real and often underestimated cost of fleet charging, and they respond directly to how charging is scheduled and managed, not just how much energy is used in total. A fleet that treats charging scheduling as an operational lever — not just a matter of plugging vehicles in whenever convenient — has meaningful control over this cost. The right specific approach depends on your utility's rate structure, which is worth getting a direct, current answer on rather than assuming based on general patterns, since rate design varies significantly by utility and changes over time.
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