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Residential Energy Storage System Regulations

NFPA 855, Standard for the Installation of Stationary Energy Storage Systems, contains requirements for the installation of energy storage systems (ESS). An ESS system is a technology that helps supplement renewable energy sources (such as wind and solar), support the country’s electrical infrastructure, and can even provide electricity to our homes during a power failure. This technology has a lot of great applications but it also has inherent fire risks so it is important to manage  risks by taking some basic precautions. NFPA 855 covers a lot of different ESS topics but this blog will focus on some of the considerations related to installing an ESS in a residential one or two family home. The exact requirements for this topic are located in Chapter 15 of NFPA 855.

What is an Energy Storage System?

An energy storage system is something that can store energy so that it can be used later as electrical energy. The most popular type of ESS is a battery system and the most common battery system is lithium-ion battery. These systems can pack a lot of energy in a small envelope, that is why some of the same technology is also used in electric vehicles, power tools, and our cell phones. ESS are often installed in homes to supplement solar panels, but they can also be used to offset the price of electricity by charging when electricity is cheap and discharging when it is more expensive.

Size limitations

The residential chapter of NFPA 855 addresses the installation of residential ESS units between 1kwh and 20 kwh. After individual units exceed 20kWh it will be treated the same as a commercial installation and must comply with the requirements of the rest of the standard. There are also limitations on how much total energy can be stored in certain areas of a household. If you go beyond those thresholds, then you need to comply with the requirements for commercial installations.

Area

Maximum Stored Energy

Utility closets, storage or utility spaces

40 kWh

Garages and detached structures

80 kWh

Exterior walls

80kWh

Outdoor installations

80kWh

 

Location

Energy storage systems can pose a potential fire risk and therefore shouldn’t be installed in certain areas of the home. NFPA 855 only permits residential ESS to be installed in the following areas:

  • Attached garages
  • Detached Garages
  • On exterior walls at least 3 ft (914 mm) away from doors or windows
  • Outdoors at least 3 ft (914 mm) away from doors or windows
  • Utility closets
  • Storage or utility spaces

ESS can be installed in any of those locations, however if the room is unfinished, the walls and ceiling need to be protected by at least 5/8 in. (16 mm) gypsum board.

Certain types of energy storage systems have the potential to discharge toxic gas during charging, discharging, and normal use. It makes sense that these types of energy storage systems are only permitted to be installed outdoors.

One last location requirement has to do with vehicle impact. One way that an energy storage system can overheat and lead to a fire or explosion is if the unit itself is physically damaged by being crushed or impacted. Because of this risk, any battery systems installed in a location where they are subject to vehicle damage needs to be protected by approved barriers, usually in the form of safety bollards. No one wants bollards installed in their garage or driveway so ideally one would be able to move their system out of reach from vehicles. This can be accomplished by either relocating the ESS to a place where vehicles can’t access or mounting it higher on the wall so vehicles can’t accidentally run into it.

Fire Detection

If there is an ESS in your home then interconnected smoke alarms are required to be installed throughout your house, including any garages or rooms housing ESS units. If you run into a situation where you can’t install a smoke alarm, such as an attached garage, a heat detector must be installed and be connected to the smoke alarms in the rest of the house.

Electric Vehicle Use

As global sales of electric vehicles seem to be exponentially growing the committee that wrote NFPA 855 thought it would be important to include requirements for houses that will use their electric vehicles as energy storage systems. There are really only two main requirements. First, any electric vehicle used to power a dwelling while parked needs to comply with the manufacturer’s instructions and NFPA 70, National Electrical Code®. Second, the use of a vehicle to power a home can’t exceed 30 days.

While there are a lot of requirements for commercial energy storage systems the rules and regulations are much more relaxed for smaller systems being installed in residential one- and two-family dwellings.

I hope you enjoyed this blog. ESS is certainly a hot topic. If you are interested in  ESS, please plan to attend either the Keeping Hazardous Environments Safe one-day conference on October 5th where ESS will be discussed during two industry panel discussions or the Global Trends and Research conference on November 2, where experts will discuss ESS explosion risks during a two-hour roundtable. All NFPA 125th Anniversary Conference Series sessions are available for one year after the live date, via on-demand.

For related training, articles, research reports, and more check out www.nfpa.org/ESS.

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Brian O'Connor
Technical Services Engineer , passionate about all things fire protection.

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