Power and energy

EV charging site-headroom worksheet

Apply an operating reserve to a site import limit, then calculate interval-by-interval charging headroom and concurrent charger capacity.

Calculate

Site and charger fleet
kW
kW
Must not exceed the entered site capacity.
kW
Use AC/site-side input, including conversion losses, not DC vehicle output.
chargers
minutes
Measured non-EV baseline
Enter complete, equally spaced interval-average values with shared boundaries. Positive means import; negative means export.

Worked example

Minimum site headroom for charging

30 kW

Interval with the least headroom
5 of 8
Full-power chargers at that interval
chargers
Site-side charging energy, theoretical upper bound
230 kWh
Capacity after the entered reserve
450 kW

Assumes continuously adjustable, fully available chargers and usable interval-average headroom throughout each interval. Subinterval peaks, minimum modulation and vehicle or departure constraints remain separate.

Method and assumptions

Formula

dispatchable charging = max(0, min(charger fleet kW, site capacity − reserve − baseline kW))

This is an active-power worksheet; it does not perform a network, phase, protection or diversity study.

Limits of this result

  • Import capacity, reserve and baseline must use the same active-power boundary with positive import and negative export.
  • The result does not check phase unbalance, voltage, transformer thermal duty, harmonics, protection, cables or connection agreements.
  • A dispatch controller also needs charger availability, vehicle energy/departure needs, command acknowledgement and a safe communications-failure state.
  • The integrated value is a theoretical site-side charging-input upper bound from interval-average baseline data; it cannot reveal subinterval peaks or conversion losses.

Technical sources

  1. EVI-X electric vehicle charging infrastructure analysis toolsNational Renewable Energy Laboratory · accessed 2026-09-14
  2. Managed charging and the gridNational Renewable Energy Laboratory · 2022-01-10

Put the value to work

Read the related engineering guidance, or carry this task into System Builder to identify the signal path and EpiSensor products.

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