Fleet EV charging installations are fundamentally different from single-charger installations at retail or workplace facilities. Fleet sites charge multiple vehicles simultaneously, often on tight overnight windows, with aggregate electrical demand that can reach several hundred kilowatts. Designing these sites correctly requires detailed electrical engineering that goes well beyond adding circuits to an existing panel. Our EV charging engineering team works on fleet sites for transit agencies, delivery fleets, utility companies, and large commercial operators across all 50 states.
What Makes Fleet EV Charging Different
Destination and workplace charging typically involves Level 2 chargers spread across a parking lot with low coincident demand. Not all chargers operate at full power simultaneously because vehicles arrive and depart at different times throughout the day. The aggregate demand is manageable and often within the capacity of existing electrical infrastructure.
Fleet charging operates differently. A fleet of delivery vehicles or transit buses returns to the depot at the end of a shift and must be fully charged before the next shift begins. If the fleet returns at 5 PM and must be ready by 4 AM, all vehicles are charging simultaneously through the night. The aggregate demand is the full charger count times the charger power level, and that peak demand occurs every night, not occasionally.
A fleet of 40 delivery vehicles charging at 7.2 kW each draws 288 kW simultaneously. A fleet of 20 transit buses charging at 50 kW each draws 1,000 kW. These are large loads that require careful service entrance sizing, transformer capacity verification, and utility coordination. Our engineering team designs systems that deliver the required energy to every vehicle without overloading any part of the electrical system.
Load Calculations for Fleet Sites
Fleet site load calculations start with a duty cycle analysis. The engineer determines how much energy each vehicle must receive per shift, how many hours are available for charging, and whether the charging window is long enough to allow a demand reduction through load management. If each vehicle needs 50 kWh and 10 charging hours are available, each charger needs to deliver an average of 5 kW, which can be accomplished with a 7.2 kW Level 2 charger with some headroom for load management.
The calculation also considers whether vehicles charge in a single peak period or stagger arrival times. Some fleet operations return all vehicles within a one-hour window, creating a very steep demand ramp. Others have staggered returns that spread the charging load over several hours and reduce the peak demand.
Service Entrance and Transformer Sizing
The service entrance must be sized for the calculated peak demand plus safety margins. For large fleet sites, this often means a new 2,000-amp or larger service or dedicated distribution switchgear. The utility transformer serving the site must have sufficient capacity for the fleet charging load plus the facility’s other electrical demands. Most fleet electrification projects require transformer upgrades because existing transformers were sized for the facility without EV load. Our EV engineering team coordinates with utilities early in the process to initiate transformer upgrade applications.
Conduit Routing and Distribution Equipment
Large fleet parking areas often span acres of paved surface. Conduit runs from the electrical room or switchgear to individual charger locations must be designed to minimize voltage drop over long distances while remaining cost-effective. A common approach is to install intermediate sub-panels or distribution boards at strategic locations within the parking area to reduce the length of the final branch circuits to each charger.
Underground conduit systems for fleet sites require coordination with pavement design, drainage structures, and any planned expansion areas. Installing conduit infrastructure during initial site development costs far less than retrofitting conduit through existing pavement later. Engineering the conduit layout for the full buildout from day one, even if not all chargers are installed immediately, reduces long-term cost.
Permit and Utility Coordination Package
The permit package for a fleet EV charging site includes a site plan showing charger locations and conduit routing, a single-line diagram from service entrance to each charger, panel schedules for all distribution equipment, load calculations, and specifications for all electrical equipment. The utility coordination package includes service application forms, load study documentation, and the engineer’s calculations supporting the requested service size. We prepare both packages simultaneously so that permit and utility applications proceed in parallel. Learn more about our EV charging services.
Frequently Asked Questions
How long does utility coordination take for a large fleet charging site?
Utility coordination timelines vary significantly by utility and by the magnitude of the requested service upgrade. Small service increases may be processed in four to eight weeks. Projects requiring transformer replacements commonly take six to eighteen months because the utility must procure equipment and schedule crews. Starting utility coordination at the earliest possible point in the project is the single most effective schedule action for fleet electrification projects.
Can existing fleet facilities use their current electrical service for EV charging?
Sometimes, but it depends on the existing service capacity and current utilization. Facilities with large electrical services and low current utilization may have room for some charging capacity without upgrades. Most facilities require at least some electrical infrastructure improvement to support meaningful fleet charging. A load study determines what is possible within the existing infrastructure.
What is smart charging and when is it required?
Smart charging systems use software to manage charging power across multiple chargers in real time, reducing peak demand by distributing available power across vehicles based on their state of charge and departure time requirements. Smart charging can reduce the required service entrance size significantly on fleet sites with flexible charging windows, reducing infrastructure costs. We design smart charging systems into fleet sites where the demand reduction justifies the added system cost.
Start Your Fleet Electrification Project
We provide complete electrical engineering for fleet EV charging sites in all 50 states. Submit your project at rightangleeng.com/get-started to get started.
References
U.S. Department of Energy, Alternative Fuels Data Center. (2024). Fleet Electrification Resources. afdc.energy.gov.
Electric Power Research Institute. (2023). Fleet Electrification Planning Guide. EPRI, Palo Alto, CA.
National Fire Protection Association. (2023). NFPA 70: Article 625: Electric Vehicle Power Transfer Systems.