Every three years, the National Fire Protection Association (NFPA) assembles technical committee members to review, modify, and add new requirements to the National Electrical Code (NEC), which enhances electrical safety in the workplace and the home. One area of recent focus is the safety of home interconnection of alternative energy technologies including photovoltaic (PV), electric vehicle (EV) charging, and energy storage systems. Modern homes can now act as energy hubs producing their own power and interacting with electric utility systems to help support the flexibility and stability of the electrical grid.
To help you keep up with the latest Code changes, here are five ways the NEC’s 2023 updates are staying focused on the safe implementation of key technologies for the electric home:
- Electric vehicles
- Interconnection of alternative energy solutions to the electric grid
- PV systems
- Using EVs to power the home Energy storage systems
1. Electric vehicles
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 buying electric vehicles (EVs). Eaton expects 40% of vehicle sales to be EVs by 2028.
Charging at a single-family dwelling, usually within a garage, allows EV owners to take advantage of stable residential electricity rates. And today more than ever, the electrical infrastructure supporting homes must be able to support the EV charging needs of the future safely.
What are the changes?
NEC 2023 added Sec. 220.57 to aid in load calculations for electric vehicle supply equipment (EVSE). Additionally, Sec. 625.40 was modified to provide flexibility in the number of EVSEs on a branch circuit. Previous requirements (NEC 2020) stating that EVSE be supplied by an individual branch circuit serving no other outlets were modified to only apply to EVSE greater than 16A or 120V when a new NEC 2023 exception is not leveraged. The new exception permits multiple EVSEs when employing an energy management system [Sec. 625.42(A)] or when the EVSE has adjustable settings [Sec. 625.42(B)].
For those applications where the EV can become a source of power for the dwelling or even the electric grid, NEC 2023 made additional changes to Sec. 625.48, adding wireless power transfer equipment (WPTE) to the already recognized EVSE technologies that incorporate power export functionality. Section 705.13 recognizes that sizing busbars and conductors can be based on an energy management system when following Sec. 750.30.
Why are these changes important?
Regardless of whether a home is new or you are upgrading a 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 the adequate capacity of the system. It can be challenging to determine whether an existing panelboard can handle the additional load. If this critical step is skipped or is incorrect, the likelihood of EV charging station failures, damage to a 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 7,200W (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. Section 625.40 now only requires an individual branch circuit for EVSE outlets greater than 16A or outlets greater than 120V. 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 Sec. 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 [Sec. 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.
A complete load analysis should be performed before installing EV chargers of any voltage, and thorough testing of load shedding capabilities should occur 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 that it is permitted to exceed the bare minimum NEC requirements in your design.
2. Interconnection of alternative energy solutions to the electric grid
Residential properties are being transformed from a simple energy load on the grid into strategic assets by incorporating bidirectional grid connectivity, distributed energy resources, and intelligent controls in their electrical systems. This approach provides many benefits, including financial incentives to the homeowner for helping electric utilities balance the grid — but also quite a few complexities when it comes to electrical safety. In 2023, NEC Art. 705 continued to evolve and address the challenges of this modern, dynamic energy ecosystem.
What are the changes?
Changes in Sec. 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 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.
Why are these changes important?
With a major increase in 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 that grid-connected homes can manage this paradigm shift safely.
3. PV systems
PV installations, especially when paired with an energy storage system, can help reduce home electricity bills by using off-peak electricity to power 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 the 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 the homeowner to lower the chance of weather-causing damage to the inverter and the home’s interior wiring.
What are the changes?
The 2023 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:
1. Be properly rated.
2. Simultaneously disconnect all current-carrying conductors that are not solidly grounded.
3. Be externally operable with an indication of open and closed.
4. Be capable of being locked per Sec. 110.25 if not within sight or within 10 feet of the equipment.
Why are these changes important?
PV systems are much different than generator systems in that the prime mover is light, making it difficult to establish an electrically safe working 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 working 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.
4. Using EVs to power the home
Vehicle-to-home (V2H) is an emerging capability that enables two-way power flow between a home and the homeowner’s EV (see Figure below). The vehicle’s battery system can be used as a backup system while being disconnected or “islanded” from the local electric grid to power critical loads in the home during unexpected outages.
What are the 2023 NEC 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. A new Sec. 625.49 recognizes the EV could be used as an optional standby power system by operating in island mode. This Code 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 Art. 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. Section 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.
Why are these changes important?
The ongoing evolution of bidirectional EVSE capabilities is great for helping homeowners gain more value from EVs and large battery banks. But it must be understood that we are at the beginning of this technological 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 fully understand the NEC when designing and installing bidirectional EVSE as bonding, grounding, sizing, and wiring must be addressed correctly.
In addition, small details in the commissioning of these systems can make all the difference. Just like a generator may not support the full load of an 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.
5. Energy storage systems
Energy storage systems (ESSs) can be a critical component of an effective and efficient system solution. These systems help homeowners maximize the full potential of their 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 NEC underscores this by closely aligning with NFPA 855.
What are the changes?
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 a new first-level subdivision (B) titled “Maintenance.”
Why are these changes important?
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.
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 the 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 in 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
Understanding the key points of the 2023 NEC updates is essential for maintaining safer homes, businesses, and communities. These changes were made following careful evaluation of real-world incidents to ultimately create a better standard for safety in both residential and commercial environments. Your commitment to understanding and implementing these updates will play a vital role in supporting a stronger electrical safety culture and safer electrical systems across America.
