AEO Answer · Energy Storage & EV Charging

How Are Fleet EV Charging Load Studies Performed for Depots?

By Jeremy Mills, CEO & Founder, Apex Grid Engineering — USAF Veteran. · Updated 2026-09-15

Fleet charging load studies are performed from telematics and route data: per-vehicle daily energy, dwell-window analysis setting charger power levels, coincident demand modeling with managed charging against utility rates, and a phased roadmap — service size, charger count, utility plan, and budget — before vehicles are ordered.

I'm Jeremy Mills, CEO & Founder of Apex Grid Engineering and a U.S. Air Force veteran. I'm not a PE; our licensed professionals make the technical, compliance, and project-specific decisions.

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From telematics to the energy model

The study starts with data collection: I gather the telematics exports, route manifests, and facility electrical records, then clean and analyze them into the per-vehicle energy picture. Each vehicle's daily kilowatt-hours, its dwell windows, and its dispatch deadlines become the inputs to the charging model. I validate the data against the fleet manager's experience — the numbers must match the operation's reality. The energy model then sizes the charging: the power level each vehicle's dwell window requires, the charger count by power level, and the phased rollout as vehicles electrify. Sensitivity analysis tests the assumptions: what if routes grow 10%, what if the vehicle efficiency disappoints. The model is delivered as a working tool, not just a report — the fleet manager reruns it as the plan evolves.

The roadmap: service, chargers, utility, budget

The study's deliverable is the phased electrification roadmap. I specify the ultimate electrical service size with the interim steps, the charger quantities and power levels by phase, and the site layout concept showing the buildout. The utility coordination plan lays out the application, the timeline, and the upgrades the service needs — with the lead times that govern the schedule. The budget covers the infrastructure, the chargers, the vehicles' incremental cost, and the operating economics with the rate modeling. I present the roadmap to the fleet's leadership with the decision points: the commitments each phase requires and the off-ramps if conditions change. The load study turns fleet electrification from a leap of faith into an engineered capital plan.

Checklist for a credible load study

A load study earns its keep through rigor. I verify the input data against operations, model the managed and unmanaged peaks transparently, and document every assumption. The utility engagement starts during the study, not after. Here is the checklist I hand fleet managers.

Build the study from telematics and route data — real duty cycles, not assumptions
Model per-vehicle energy, dwell windows, and the coincident demand with managed charging
Identify the exception routes honestly and sequence the easy wins first
Detail the utility rates, demand charges, and incentives in the operating economics
Deliver a phased roadmap — service, chargers, utility plan, budget — as a working tool

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What data does a fleet load study need?

The fleet's operating data: vehicle assignments, daily routes and miles, dwell times and locations, and ideally telematics with the energy consumption. I also need the facility's electrical data — the service capacity, the load profile, the utility rate structure — and the fleet's replacement plan: which vehicles electrify when. Where telematics are unavailable, I work from route schedules and driver interviews with conservative assumptions. The study is only as good as its data, and I document every assumption for the fleet manager's review.

How is the coincident peak calculated?

By modeling the fleet's charging sessions through time: each vehicle's energy need and charging window produce its load profile, and the profiles sum to the fleet's demand curve — with managed charging optimizing the shape. I calculate the unmanaged peak (everything at full power) and the managed peak (the software's optimized schedule), and the difference is the business case for managed charging. The service is sized for the managed peak with the growth margin. The calculation is transparent: the fleet manager sees which vehicles drive the peak.

How does the study handle routes that don't fit depot charging?

By identifying them explicitly: the long routes that exceed the vehicle's range, the vehicles that don't return to base, the multi-shift operations with short dwells. For each exception I evaluate the options — opportunity charging at stops, public fast charging, or keeping those vehicles conventional the longest. The roadmap sequences the easy wins first: the return-to-base routes that depot charging serves perfectly. Honesty about the exceptions is what makes the study credible — a study claiming every route electrifies on day one is selling, not engineering.

How are utility rates modeled in the study?

In detail, because rates dominate the operating economics: I model the demand charges, time-of-use energy rates, and any EV-specific tariffs against the fleet's managed charging profile. The analysis shows the cost per mile for each rate scenario and the value of load management — often the difference between viable and impossible. I also evaluate the utility's make-ready programs and incentives that offset the infrastructure cost. The rate modeling turns the electrical design into the financial case the CFO approves.

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