#1. Is it the intent of NEC 702 to require an optional standby source to be installed if an automatic transfer switch is provided at the time of the service equipment installation?
#2. Am I correct in understanding that NEC 702 permits the ATS to be installed without the optional standby source, since the ATS by itself is only equipment and does not constitute an optional standby system?
Interpretation #9515
Published April 14, 2026
Original Request
- Code Version
- 2023
- Code
- ELECTRIC
- Code Description
- Chapter
- 7
- Section
- 702.1
- Topic
- Transfer switch installation without a generator
Question
Answer Published 04/02/2026 at 1:13 PM
The ATS is not the optional standby system; it is electrical equipment that facilitates a future connection.
Short answer:
#1. No.
#2. Yes.
Short answer:
#1. No.
#2. Yes.
Commentary
NEC Section 702.1 Scope talks about a complete energy system capable of supplying power to a premises wiring in lieu of the primary energy source as an Optional Standby mode where there is no legally required standby power requirement due to the classification or use of a building.
Since the ATS mentioned in the request for interpretation is not a system capable of delivering energy/power but rather a component of the electrical system of the structure, that can accommodate the delivery of that energy/power when installed, it is only a piece of equipment that would facilitate the connection of another source of energy, and not the entire system as described in Section NEC 702.1 Scope.
The ATS is similar to a Bi-Directional EV charging port in a structure, in that it is only a device to allow the transfer of energy from one point to another. The ATS may be installed much the same as an EV port, or a receptacle outlet for a refrigerator or range, where there is no requirement in the Code for specific appliances, only if provided.