How much energy can a ESS unit store?

Individual ESS units shall have a maximum stored energy of 20 kWh per NFPA Section 15.7. NFPA 855 clearly tells us each unit can be up to 20 kWh, but how much overall storage can you put in your installation? That depends on where you put it and is defined in Section 15.7.1 of NFPA 855.

Who should consider adding energy storage to a commercial building?

This guide is intended for anyone investigating the addition of energy storage to a single or multiple commercial buildings. This could include building energy managers, facility managers, and property managers in a variety of sectors.

Are energy storage systems safe for commercial buildings?

For all of the technologies listed, as long as appropriate high voltage safety procedures are followed, energy storage systems can be a safe source of power in commercial buildings. For more information on specific technologies, please see the DOE/EPRI Electricity Storage Handbook available at:

How many ESS units can be installed on a wall?

The diagram shows that each ESS unit can have a maximum rating of 20 kWh, and if you’re going to install two units, let's say outside on your wall, you need to have the appropriate spacing between those units and three-feet separation from doors and windows per NFPA 855 15.6.1.

What is energy storage?

Basics of Energy Storage Energy storage refers to resources which can serve as both electrical load by consuming power while charging and electrical generation by releasing power while discharging. Energy storage comes in a variety of forms, including mechanical (e.g., pumped hydro), thermal (e.g., ice/water), and electrochemical (e.g., batteries).

What are the different types of energy storage?

Energy storage comes in a variety of forms, including mechanical (e.g., pumped hydro), thermal (e.g., ice/water), and electrochemical (e.g., batteries). Recent advances in energy storage, particularly in batteries, have overcome previous size and economic barriers preventing wide-scale deployment in commercial buildings.