Energy management systems (formerly PCS) for solar

What the code requires

In the 2023 NEC, 705.13 is titled Energy Management Systems (EMS). In 2020 the section covered Power Control Systems, and many people still use the PCS name. Revisions for the 2026 NEC return to the power control system name, but California's current code is based on the 2023 NEC.

The rule itself is short. An energy management system that meets 750.30 may limit the current and loading on busbars and conductors fed by one or more interconnected power production or storage sources. An informational note says a listed power control system is one type of EMS: it monitors multiple sources and controls current to keep busbars and conductors from overloading. The related product standards are UL 1741 and UL 916.

Under 705.28(A)(2), where an EMS controls the equipment, the EMS current setpoint is used as the source's maximum current, and that number then goes into the 705.12 busbar calculations and the 705.28 conductor calculations. A lower setting means a smaller number goes into that math.

On the job

• The busbar and conductor calculations use the EMS current setting, so the setting in the equipment needs to match the number used in those calculations.
• Under 750.6, new in the 2023 NEC, the energy management system must be listed.

What changed in 2023

The 2023 NEC replaced the 2020 power control system section and its detailed (A) through (E) rules with this short EMS rule, and Article 750 now requires an EMS to be listed.

Related sections

• NEC 750.30
• NEC 705.12: The 120% rule for solar and battery breakers
• NEC 705.28
• NEC 220.70

Where this comes from

• NFPA: 2026 NEC (A2025) CMP-4 First Draft public input report, reprinting 2023 text
• Mike Holt: Summary of the 2023 Changes to the NEC
• NFPA: 2026 NEC (A2025) CMP-4 Second Draft report (SR-7638)
• Electrical Contractor: Concluding the 2023 Code Review (M. Earley), Sep 11 2023
• Read the official NEC free at NFPA