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.

How far apart should storage units be positioned?

Therefore, if you install multiple storage units, you have to space them three feet apart unless the manufacturer has already done large-scale fire testing and can prove closer spacing will not cause fire to propagate between adjacent units.

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 are energy storage systems (ESS)?

June 06, 2023 by Hubert Biteau, PhD, P.E. Energy Storage Systems (ESS) are a source of available and reliable power that can provide flexibility to electrical grids during peak usage and assist with load management and power fluctuations.

How many kWh can a house use?

The diagram also shows that if you're inside the home, you can go up to 40 kWh; if you’re outside the home on the wall, you can go up to 80 kWh; and if you're in a garage, you could also have 80 kWh there. All locations will require multiple units to reach the 40/80 kWh limit, which is fine as long as they're adequately spaced per this code.