Power for EV fleet
charging depots.
Adding vehicles and chargers can outgrow a depot’s grid connection long before the utility can upgrade it. Plan the charging power you need around the connection you have.
The constraint
Fleets, transit agencies and school districts are adding electric vehicles faster than many depot connections can grow. A service or transformer upgrade can take longer than the vehicle delivery schedule, and demand charges rise with the charging peak. How long grid connections take, with sources.
The depot is becoming a data site too
Connected and increasingly automated fleets generate data at the depot: charging management, telematics, video and vehicle software updates. More depots will host a small data room next to the chargers, from a few racks up to around 1 MW, with denser racks every year. That load runs around the clock while charging peaks overnight, so plan both together. On-site power for edge compute.
Size from the schedule, not the chargers
Charger nameplate ratings are not demand. In an illustrative calculation, 250 chargers at 350 kW each total 87.5 MW of nameplate power; the power a depot actually needs depends on how many vehicles charge at once, their daily energy use, dwell time and departure times. Start with a measured or engineered load profile.
Questions to answer before sizing
- Number of vehicles, daily kilowatt-hours per vehicle and future fleet size.
- Dwell time and departure schedules.
- Charger power ratings and whether charging can be managed.
- Any on-site compute or data room planned for the depot.
- Existing connection capacity, tariff and demand charges.
- Yard space, fuel availability, permitting and noise limits.
Options to compare
Managed charging keeps total demand under the connection limit and may be enough when vehicles sit long enough to charge slowly. Battery buffers recharge from the grid and deliver short high-power sessions. On-site generation adds sustained capacity when the fleet’s daily energy exceeds what the connection can deliver. A utility upgrade may still be the long-term answer. Many depots combine these.
Where the DOR fits*
The DOR is being developed as compact behind-the-meter capacity. Engineering targets: 200 kW electrical output per unit, parallel operation (five units would target 1 MW), a 1.4 × 1.0 × 2.0 m package of about 15 sq ft, 700 kg, about 90 kVA per cubic meter, 69 dBA at 5 m, and a grid-forming inverter for grid-tied, standalone or microgrid operation. Planned fuels are natural gas, CNG, LPG, biofuel and hydrogen blends. An integrated DOR prototype has not yet been built or tested; these are targets subject to integrated-system testing, third-party validation and certification, and first pilot deployments are planned for 2027. See the technology and datasheet.
Common questions
How can EV depots get power faster than waiting for a utility upgrade?
Evaluate managed charging, battery storage and modular on-site generation behind the meter. The pre-pilot DOR targets 200 kW in a package of about 15 sq ft and 700 kg and is designed for multi-unit parallel operation; a five-unit configuration would target 1 MW. Handling, site work, permitting, fuel and interconnection requirements must be confirmed during engineering review.
Our school district bought electric buses and the depot cannot charge them all. What can we do?
Start with the charging schedule: buses often sit for long periods, so managed charging may cover much of the need. Where the connection still falls short, behind-the-meter generation or storage can be evaluated. Fuel, emissions, noise, permitting and interconnection all require site-specific review.
Do we need on-site generation if we use managed charging?
Not always. If dwell time lets vehicles charge slowly within the connection limit, managed charging and storage may be enough. Generation matters when the fleet’s daily energy need exceeds what the connection can deliver over the available hours.
Has the DOR been deployed at a site like this?
No. The DOR is pre-pilot: an integrated prototype has not yet been built or tested, and first pilot deployments are planned for 2027. Figures on this page are engineering targets or illustrations, not results from installed projects.
Plan your depot’s power.
Bring your fleet plan, charging schedule and current connection. We’ll help define what to evaluate. Site fit depends on permitting, fuel supply, interconnection and engineering review.
Discuss your site