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Designing EV Charging Station Infrastructure

In Part 2 of the series, Design Considerations for Electric Vehicle Charging Stations, we explored key considerations for a potential electric vehicle charging project. Now, after the green light to include EV charging on a project, we will dive into the main infrastructure design components necessary for a successful installation.

At this point in a project’s development, to move forward with confidence, it is important to identify a basis-of-design product to plan infrastructure requirements around. Reaching out to electric vehicle supply equipment (EVSE) manufacturers and service providers at this stage can be helpful to fully understand implications and requirements for the wide range of options available.

Engineers and architects must holistically consider infrastructure implications in a few key areas:

  • Day one and future EV charging needs. Review locally applicable codes for infrastructure requirements such as spare circuit breakers in panels. Also consider future-proofing measures which are cheap to put in place early in design and help facilitate future EV installations, such as installing conduit pathways from an electrical room out to parking areas.
  • Proximity from planned EV parking spaces to the site’s utility service entrance, or, in larger installations, a downstream panelboard with sufficient capacity.
  • Conduit size and pathway (e.g. surface-mounted, underground trench), and EVSE mounting type (wall vs. pedestal/bollard).
  • Branch circuit conductor sizing.
    • Consider maximum input power rating (kW) of the particular model of EVSE to be installed and follow all manufacturer’s installation requirements to appropriately size the power supply.
    • EVs are understandably considered “continuous” loads by the NEC, expected to be in operation for ≥3 hours and must be calculated at 125% of the input current when sizing conductors, overcurrent protection devices, and panelboard capacity. The code offers no exception for 100% rated circuit breakers in this application.
    • Size conduit with consideration for conductor voltage drop and code required de-rating if multiple conductors share a single conduit.
  • Efficiencies in building electrical service capacity and cost can be achieved by incorporating Automatic Load Management Systems (ALMS) in the design, as described in NEC article 625.42. This approach can help avoid expensive capacity upgrades by using software to dynamically monitor and optimize EV charging energy consumption relative to the site’s other base loads, time-of-use utility rates, electric grid carbon intensity, and other variables.
    • Circuit Sharing: Serve multiple EV outlets from a single branch circuit without exceeding the rated load capacity of the circuit.
    • Panel Sharing: Connect more EVSE stations to a panelboard than otherwise permitted if using straight NEC load calculations.
    • Site/Transformer Sharing: “Oversubscribe” an electric service capacity by setting a power ceiling value to limit peak demand when service capacity is limited.
  • When an EVSE model rating requires a supply voltage above 150V to ground or a circuit breaker above 60A, then a readily accessible disconnect switch is required by code, capable of being locked in the open position. Note that while this is a code minimum requirement, a local disconnect may still be a good design feature for improved safety, maintenance, or a future-proofing measure to enable higher-capacity EVSE upgrades down the road.
  • Get pricing and constructability feedback from the contractor responsible for building the design.


Electric Vehicle Charging Station series links:

Electric Vehicle Charging Stations 101

Design Considerations for Electric Vehicle Charging Stations

Designing EV Charging Station Infrastructure

Building Sustainability with Electric Vehicles

The Future Impact of Electric Vehicles on Transportation Planning

Do you have questions about electric vehicle charging stations? Don’t hesitate to reach out to SSR for our guidance and expertise. Email and someone will promptly follow up.