NEC Code Quotes (2023 Edition)

NEC 220.70 Energy Management Systems (EMSs)

"If an energy management system (EMS) is used to limit the current to a feeder or service in accordance with 750.30, a single value equal to the maximum ampere setpoint of the EMS shall be permitted to be used in load calculations for the feeder or service. The setpoint value of the EMS shall be considered a continuous load for the purposes of load calculations."

NEC 625.42 Rating (Electric Vehicle Power Transfer System)

"Service and feeder shall be sized in accordance with the product ratings, unless the overall rating of the installation can be limited through controls as permitted by 625.42(A) or (B)."

(A) Energy Management System (EMS). "Where an EMS in accordance with 750.30 provides load management of EVSE, the maximum equipment load on a service and feeder shall be the maximum load permitted by the EMS."

NEC 750.30 Load Management

"Energy management systems shall be permitted to monitor and control electrical loads and sources... If an EMS is used to limit the current on a conductor... A single value equal to the maximum ampere setpoint of the EMS shall be permitted for one or more of the following: (1) For calculating the connected load per 220.70..."

Why an EMS Removes the Need for Costly Upgrades

Under traditional electrical code rules, an electrician must calculate the "load" of a home by adding up the potential power usage of all appliances. If you add a high-power device like an Electric Vehicle (EV) charger, this calculation often exceeds the capacity of an older electrical panel (e.g., 100 Amp service), legally requiring a homeowner to pay thousands of dollars for a "service upgrade" to a larger panel (e.g., 200 Amp).

NEC 220.70 and 625.42(A) introduce a critical exception to this rule. They state that if you install an Energy Management System (EMS), you do not have to use the EV charger's maximum potential power for your safety calculations. Instead, you can use the "maximum ampere setpoint" programmed into the EMS.

How it works in practice:

  • Without EMS: Your home uses 80 Amps at peak. You want to add a 48 Amp EV charger.

    • Calculation: 80A + 48A = 128A.

    • Result: Your 100A panel is "overloaded" on paper. You must pay ~$2,500–$5,000 to upgrade to a 200A panel.

  • With EMS (ChargeXcel): The EMS monitors your home's total power in real-time. You set a "limit" (setpoint) of 80 Amps for the whole house.

    • Calculation: The Code allows you to use your setpoint (80A) as the total calculated load.

    • Result: 80A is within your 100A panel's rating. No panel upgrade is required. When your home uses less power (e.g., at night), the EMS automatically allows the EV to charge at full speed. If you turn on the oven and dryer, the EMS temporarily slows down the EV charging to ensure the total never exceeds 80 Amps.

In short, these codes allow technology to manage safety dynamically, legally replacing the need for expensive physical copper and heavy hardware upgrades.

Our Approach

This video from Mike Holt explains the 2023 NEC section 220.70 and illustrates how energy management systems can be used to limit electrical current to avoid service upgrades.

Great Minds think Alike

Just like in the video, the podcaster immediately recognized the need for an EMS that does more than simply cut power during an overload. He wanted an EMS that can throttle charging instead of shutting it off. Some EVSEs can add this capability, but they are limited to their own closed, wired systems. Only ChargeXcel can work wirelessly with EVSEs and EVs in a brand-agnostic way.