Power Management FAQ

What is Power Management?


As electric vehicles (EVs) become more prevalent, demand for EV charging infrastructure increases. Because few buildings were designed for EV charging, your building may not have sufficient electrical capacity to support all of the charging spots you want to install to meet growing demand for charging from customers, employees, visitors and other EV drivers.

Because adding electrical capacity can be expensive, we developed Power Management software to let organizations install more EV charging stations, intelligently share existing power among them and avoid costly upgrades. Based on our assessment of the electrical capacity at your location, we can help you configure the maximum aggregate electrical load for each group of charging stations. ChargePoint® cloud services will intelligently manage the individual power output of each charging station (or port) to ensure the maximum load set is never exceeded.

Why would I use Power Management?


When EV charging stations are available at a location, people who frequent the location may become more likely to drive electric. The 2016 U.S. Department of Energy Workplace Charging Challenge found that people with access to charging at work were six times more likely to buy an EV, for example. ChargePoint Power Management software allows organizations to meet this growing demand by installing more charging spots than would otherwise be supported by the available electrical service, avoiding the time, expense and effort required to upgrade infrastructure.

Power Management can also be used to manage ongoing electricity costs by avoiding utility demand charges, which can become the largest component of electrical bills for some organizations. Station managers can set a power ceiling below the threshold for demand charges to make sure that power use from charging stations never exceeds that ceiling and never incurs demand charges. At locations where the differential in electricity costs is high, the savings can be substantial.

How does Power Management work?


ChargePoint Power Management software uses customizable algorithms to intelligently share power among stations so every car charges as fast as possible, without ever exceeding the rated electrical capacity for the site.

A simple example illustrates how one of the intelligent power sharing algorithms (“Equal Charge”) works. If three charging stations are sharing a single 40-amp (A) circuit:

  • The first vehicle that plugs into the group of power-managed stations draws full power (32A).
  • As additional vehicles plug in, they draw full power until the configured power limit is reached.
  • When the power limit is reached, the Power Management algorithm divides the available power budget equally among any additional vehicles that are plugged in. In the example, when a second vehicle plugs in, both vehicles receive 16A, while three vehicles sharing 32A each receive about 10A.
  • When a car unplugs or is fully charged, the power it was consuming is reallocated equally among the remaining cars.

The example illustrates the “Equal Charge” algorithm, where power is shared equally among all of the cars that are plugged in at any given time, but ChargePoint supports other methods of sharing power to meet the needs of different organizations. Our solutions engineering team will work with you and your electrical contractors to decide on the optimal configuration for your site.

How do I implement Power Management?


Electrical contractors who install charging stations need to assess the electrical capacity at sites where Power Management will be implemented and work with station owners to determine how the stations will be used (how long EVs will be parked). This information will provide the input needed to choose the power management configuration following ChargePoint guidelines.

Our solutions engineering team will work with your electrical contractors to select the best power sharing algorithm for your location and configure the aggregate load for each group of charging stations. Then our Cloud Services will intelligently manage the individual power output of each station (or port) to ensure the maximum load is never exceeded no matter how many EVs plug in.

Power Management software can be configured to share power at a circuit, panel, site or transformer level, or any combination of these elements. Our software ensures the load limit is never exceeded at any level: circuit, panel, or site.

What are the recommended oversubscription ratios?


The “oversubscription ratio” refers to the proportion of charging stations installed compared with the rated capacity. An oversubscription ratio of 4:1 refers to installing four charging stations where only one is rated. ChargePoint solutions engineering will work with your electrical contractors to understand site electrical capacity and charging requirements to recommend the optimal oversubscription ratio, based on factors such as how long drivers stay parked at your location. The following oversubscription ratios aim to deliver the equivalent of three hours of standard 6.2 kW charging, adding about 18 kWh or 60-75 miles of range, in specific contexts:

For long-term parking (eg, airport parking):

  • Deliver the equivalent of three hours of charging in 24 hours
  • Recommended ratio: 8:1

For overnight parking (eg, fleets):

  • Deliver the equivalent of three hours of charging in 12 hours
  • Recommended ratio: 4:1

For all-day parking (eg, workplaces, apartments and condos):

  • Deliver the equivalent of three hours of charging in 8 hours
  • Recommended ratio: 2:1

For short-term or hourly parking:

  • Don’t oversubscribe—run full power

What’s the difference between circuit, panel and site level sharing?


Power Management supports various algorithms for delivering additional charging capacity:

Circuit Sharing allows multiple 40A stations (typically two to three) to share a single 40A circuit without exceeding the rated load capacity of the circuit.

Panel Sharing allows more stations to be installed than the panel capacity allows.

Site or Transformer Sharing sets a power ceiling to limit the aggregate instantaneous load for all charging stations if the overall power available at a site is limited by a transformer.

Does Power Management meet electrical code? Will electrical inspectors approve it?


Prior to 2014, the National Electrical Code required every charging station to be provisioned on a dedicated circuit rated for 100% of the station’s electrical service capacity; oversubscription of electrical service was not permitted. However, EV charging stations don’t need full power when they’re not in service or when EVs are plugged in but not charging, so the National Electrical Code added a provision in 2014 to allow EV charging stations (also called electric vehicle supply equipment, or EVSE) to use “an automatic load management system” to manage the load on the stations. ChargePoint station installations using Power Management will be approved in states that have adopted the 2014 National Electrical Code (most states have), which allows oversubscription in Provision 625.41.

ChargePoint stations are also UL Listed as energy management devices, which validates the safety of the system and helps gain approval from inspectors. Our solutions engineering team will develop site specifications to share with electrical inspectors for approval. We also engage with electrical inspectors to increase their knowledge and awareness of features like this.

How do I enable Power Management on my stations?


Simply reach out to ChargePoint’s solutions engineering team at solutionsengineering@chargepoint.com to get started with Power Management.

How can I monitor Power Management?


As a station manager, you have two ways to monitor Power Management from your ChargePoint account:

  1. In the Manage Energy tab, click on Share Power to see how your stations have been configured to share power. There’s also a graph of power use in real time.
  2. In the Reports Tab, click on Analytics. Choose the Energy report to see energy use over time.

How does Power Management affect EV drivers?


We made the driver experience a priority when designing our Power Management features. When drivers plug into stations that are using Power Management, they get a notification that their vehicle may charge more slowly than usual, but will still receive a full charge. As with all ChargePoint stations, drivers can also check their real-time charging status in the ChargePoint app to see how the charge is progressing and find out when their car is fully charged.

Power Management is not likely to affect the average charging time for a driver. For example, at a large workplace with more than 50 active ports, average charging time went from about 2 hours to about 2.5 hours with Power Management. In this case, drivers were parked for more than 5 hours on average, so Power Management had no effect on their daily routine. Understanding how long drivers are typically parked at your location will be key in determining how to configure Power Management.

How much does it cost? What stations are supported?


ChargePoint can recommend the right cloud plan to support your needs, which may include Power Management. Currently, the CT4000 and CPF50 station families support Power Management with the appropriate cloud plan.