Motivated by advantages such as fuel savings, reduced maintenance costs, enhanced performance and the ability to slash greenhouse gas emissions, a growing number of Americans are hitting the road to electric vehicle (EV) ownership. In fact, Eaton expects 40% of vehicle sales to be EVs by 2028.

Charging at a single-family home, usually within a garage, allows EV drivers to take advantage of stable residential electricity rates. Today more than ever, the electrical infrastructure supporting homes must be able to safely support the EV charging needs of the future. 

What are the changes?

NEC 2023 added Section 220.57 to aid in load calculations for electric vehicle supply equipment (EVSE).

Additionally, Section 625.40 was modified to provide flexibility in the number of EVSE on a branch circuit. Previous NEC 2020 requirements stating that EVSE be supplied by an individual branch circuit serving no other outlets were modified to only apply to EVSE greater than 16 amperes or 120 volts when a new NEC 2023 exception is not leveraged. The new exception permits multiple EVSE when employing an energy management system [625.42(A)] or when the EVSE has adjustable settings [625.42(B)].

For those applications where the EV can become a source of power for the structure or even the electric grid, NEC 2023 made additional changes to Section 625.48, adding wireless power transfer equipment (WPTE) to the already recognized EVSE technologies that incorporate power export functionality. And 705.13 recognizes that sizing busbar and conductors can be based on an energy management system when in accordance with 750.30.

What should I know?

Regardless of whether your home is new or you are upgrading your home’s electrical system to support EV charging, the infrastructure must have the capacity necessary to accommodate the EV load. A load calculation must be performed to determine adequate capacity of the system. It can be challenging to determine whether an existing panelboard can handle the additional load, but if this critical step is skipped or is incorrect, the likelihood of EV charging station failures, damage to your home’s electrical system or EV and even injury increases.

When determining the additional load of the EV, the new NEC requirements provide options. EVSE loads can be calculated at either 7200 watts (volt-amperes) or the nameplate rating of the equipment, whichever is larger. EVs and charging equipment are increasingly common in new and existing residences. This increased popularity of EVs will make load demands for these vehicle charging stations a critical issue in future code cycles.

It is also important to keep in mind that an individual branch circuit for Level 1 charging is no longer required. As noted above, Section 625.40 now only requires an individual branch circuit for EVSE outlets greater than 16 amperes or outlets greater than 120 volts. Requiring an individual branch circuit for a 15A or 20A receptacle outlet to serve a Level 1 charger was considered excessive. The existing receptacle requirement for garages found in 210.52(G)(1) requiring at least one receptacle outlet installed in each vehicle bay for one-, two- and multi-family dwellings is considered adequate for plugging in a Level 1 EV charger.

You may be able to leverage revised code language that provides an exception permitting a single branch circuit to supply more than one EVSE when the loads are managed by an energy management system or when the EVSE has adjustable settings [625.42(A) or (B)]. Although intelligent energy management systems can shed loads to prevent multiple sources from overloading available electrical capacity, it is important to understand these technologies and the codes dictating their safety are still very much in refinement.

I recommend a complete load analysis be performed prior to installing EV chargers of any voltage and thorough testing of load shedding capabilities to ensure critical home loads are not sacrificed when the demand from EV charging outsizes available panel capacity. Place the needs of the application first, keeping in mind it is permitted to exceed bare minimum NEC requirements in your design. 

Many homeowners have adopted a Home as a Grid approach that transforms residences from a simple energy load on the grid into a strategic asset by incorporating bidirectional grid connectivity, distributed energy resources and intelligent controls.

This approach can provide many benefits, including financial incentives to the homeowner for helping utilities balance the grid — but also quite a few complexities when it comes to electrical safety. In 2023, NEC Article 705 continued to evolve to address the challenges of this modern, dynamic energy ecosystem.

What are the changes?

Changes in Section 705.11 now recognize the conductors and equipment directly connecting the electric power production sources to the line side of the service disconnecting means as service conductors and service equipment. This brings new requirements for connections of PV systems to the line side of the service disconnecting means, specifically around how splices or taps are made to service conductors and how the PV disconnect should be grounded and bonded, located and labeled.

The changes found in 705.11 bring clarity to installation requirements addressing recognized conflicts in code requirements. With clarity in requirements, installers now have clear direction on the proper equipment to meet the needs of the installation.

What should I know?

With a major increase of energy storage, renewables and other low-carbon technologies on the horizon, the energy transition is fundamentally transforming the way power systems work. Adopting the latest version of the NEC is essential to ensure grid-connected homes can manage this paradigm shift safely.

PV installations, especially when paired with an energy storage system, can help homeowners lower electricity bills by using off-peak electricity to power home loads and maintain resilience in the event of grid power failure. The recent rise in popularity of this technology makes it critical to know what it takes to safely connect solar PV to home energy systems.

If electric maintenance is being performed on the PV system or connected electric grid, being able to disconnect your PV system from the grid is an important safety feature.

Disconnects are an essential component for any size PV installation, providing the ability to quickly stop the inflow of power in the event of a fire. In the event of severe weather, such as tornadoes, hurricanes, wildfires or severe electrical storms, disconnects also allow you to lower the chance of weather causing damage to the inverter and the home’s interior wiring.

What are the changes?

The newest edition of the NEC has improved the focus and elevated the importance of providing a disconnecting means to disconnect AC PV modules, fuses, DC-to-DC converters, inverters and charge controllers from all conductors that are not solidly grounded.

Section 690.15 has been modified to add clarity to existing requirements around equipment disconnecting means, reminding installers and inspectors that they must:

• Be properly rated
• Simultaneously disconnect all current-carrying conductors that are not solidly grounded
• Be externally operable with indication of open and closed
• Be capable of being locked in accordance with 110.25 if not within sight or within 10 feet of the equipment

What should I know?

PV systems are much different than generator systems in that the prime mover is light, making it difficult to establish an electrically safe work condition. In addition, PV systems are much more likely to also include an energy storage system, which increases the number of sources of energy and adds complexity for electrical workers and homeowners. This makes a disconnect for isolating equipment in PV systems very important to maintain safety. 

AC and DC disconnects are crucial safety equipment that can help you establish an electrically safe work condition by isolating PV system equipment for safety. In addition to ensuring the devices have proper ratings, it is critical to ensure disconnects are readily accessible for the homeowner and electrical worker.

Vehicle-to-home (V2H) is an emerging capability that enables two-way power flow between your home and your EV. This means in addition to charging your EV, you can use your EV battery as an Article 702 backup system while being disconnected or “islanded” from the local electric grid to power critical loads in your home during unexpected outages.

What are the changes?

The 2023 NEC continues the journey of recognizing bidirectional current flow as it relates to the EV that began during the 2020 NEC Code cycle. New Section 625.49 recognizes the EV could be used as an optional standby power system by operating in island mode. This section requires that EV power export equipment (EVPE) and bidirectional EVSE be permitted to be a part of interconnected power systems operating in an island mode condition.

Another related and significant change was also made to Article 702, Optional Standby Systems. Section 702.5 now recognizes that an optional standby system doesn’t just consist of a generator but could also consist of interconnection equipment. And 702.4 was modified to ensure when the connection of a load to the interconnected system is automatic, the optional standby system, or interconnected system, must be sized for the load or an energy management system must be used to curtail the load.

What should I know?

The ongoing evolution of bidirectional EVSE capabilities is great for homeowners looking to gain more value from their investments in EVs and their large battery banks.

It must be understood that we are at the beginning of this technology roadmap and because of this, the technology itself and proven safety standards are not yet completely refined. Systems employing bidirectional EVSE capabilities are complex and it is critical to consult with a trusted contractor when designing and installing bidirectional EVSE as bonding, grounding, sizing and wiring must be addressed correctly.

Also, small details in the commissioning of these systems can make all the difference. Just like a generator may not support the full load of your electrical panel, many EV batteries would be completely overwhelmed when asked to support the load of an entire house.

For this reason, the system needs to be sized correctly or an energy management system should be installed to ensure the battery is capable of safely keeping the most critical (e.g., refrigeration, life support, HVAC) systems afloat when a lengthy and unexpected utility outage arises.

Those who install PV systems realize energy storage is a critical component of an effective and efficient system solution. We’re seeing more and more energy storage systems (ESSs) installed to help owners maximize the full potential of onsite renewable energy installations.

Several electrical industry references offer guidelines and best practices for the installation and testing of battery energy storage technology. The two most recent code developments for energy storage systems are:

• NFPA 855: Standard for the installation of ESSs
• UL 9540A: A test method for fire safety hazards associated with propagating thermal runaway within battery systems

Much like other electrical infrastructure equipment, making sure ESSs are periodically maintained is important for the overall safety and effectiveness of the installation — and the 2023 version of the NEC underlines this by closely aligning with NFPA 855.

What are the changes?

Making sure ESSs operate correctly at the time of installation requires special attention at the time of installation, and ensuring the ESSs continue to function over their life requires continuous maintenance. Section 706.7 was modified to include “commissioning” as reflected in its new title, “Commissioning and Maintenance of Energy Storage Systems.” This section now includes two first-level subdivisions, (A) Commissioning and (B) Maintenance. New first-level subdivision (A) requires ESSs to be commissioned upon installation in other than one- and two-family dwellings. The maintenance requirements that were in the previous edition of the NEC became new first-level subdivision (B) titled “Maintenance.” 

What should I know?

Testing and maintenance are key to getting the best performance from any battery system, whether traditional storage batteries or an ESS — but testing for those two battery types differs substantially. By understanding the relevant codes and standards and the variety of testing methods these systems require, you’ll be able to work with any battery system safely and efficiently.

For applications other than one- and two-family dwellings, ESSs must be commissioned upon installation. In these applications, ESSs must also be maintained in proper and safe operating conditions per the manufacturer’s requirements and industry standards. You can reference Chapter 32, “Battery Energy Storage Systems,” of NFPA 70B, “Standard for Electrical Equipment Maintenance,” for more information on proper maintenance of these systems. A written record of the system maintenance must be kept and include records of repairs and replacements necessary to maintain the system in a proper and safe operating condition.

Battery safety is a critical factor to the technology’s widespread adoption in the energy marketplace. A commitment to safety when it comes to the installation and operation of these systems will enable the energy transition with a more dynamic ecosystem capable of providing much more sustainable electricity than ever before. 

Closing thoughts

Powerful trends are at hand enabling homeowners to reap the benefits of alternative energy solutions, create more flexible power systems and transform what is possible for the home as an energy source. These trends are also unlocking easier management of electrical loads for household activities that have traditionally been powered by fossil fuels.

Because this Home as a Grid approach can break traditional electrical boundaries and enables far more flexibility in how and when you use your electricity, it is paramount these technologies are installed and maintained in compliance with the latest electrical safety standards. The NEC is helping – and will continue to help homeowners and contractors do just that. 

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