What makes the inspection of a stand-by generator so different from the inspection of  an energy storage system?

In today’s dynamic energy environment, new methods have emerged for managing power sources and their integration into building wiring systems, as well as exporting surplus electricity generated onsite back into the utility grid. For example, as more energy storage systems are being installed, technology has advanced to keep up with the evolving energy landscape. The speed of adoption has created some misunderstandings as to what a“transfer” switch is. 

A stand-by generator is typically connected through a transfer switch. These units are neither synchronized with, nor are they ever connected to, the utility grid. The load is supplied by either the generator or the utility, but never both sources. 

By contrast, a utility-interactive energy storage system is synchronized with the utility and always connected to both the load and the utility unless the utility is de-energized. If the utility grid goes down a microgrid interconnect device (MID) isolates the utility source. This MID acts differently than a transfer switch. 

Incorrect installations can result when the distinction between parallel power production sources like an energy storage system, and a generator-based optional standby system connected through a transfer switch, is not fully understood. 

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This short course, Energy Storage Systems and Generators: Some Critical Distinctions, will clarify when a system is able to produce electricity in parallel with the grid and highlight the applicable code requirements for utility-interactive interconnected energy storage systems.