The primary reason that most people install an energy storage system at home is for the benefit of resiliency: Batteries provide emergency backup power in an outage. Though infrequent in most parts of the country, grid outages occur, and energy storage allows you to keep the lights on even when the rest of your block has no power.
Given how many batteries exist in everyday life, you're probably very familiar with how they operate: they store power for use later. During an outage, energy storage creates a miniature "energy island" for your home or business. So even when the rest of your neighborhood is without power, you can pull from your battery to keep your lights on.
It's like how you can use a power bank to charge your phone if you're away from an outlet and are running out of juice; instead of plugging into a wall outlet to charge your phone with the grid, you can plug into a tiny, pocket-sized battery to recharge your device. You're doing this when the grid goes down; since pulling electricity from the grid is no longer an option, you're drawing from your battery instead.
Notably, the types of batteries you install for your home or business have a limited storage capacity and power; as such, most batteries are unable to back up your entire home. Instead, when you install an energy storage system in your home or business, you'll be asked to choose which circuits (i.e., outlets, appliances, and sections of your home) to back up in the event of an outage on a "critical loads panel." Suppose you'd like to avoid this step and maintain some additional flexibility to change what parts of your home you back up and when; it's worth looking into smart electric panels, which can help you maximize the backup power and flexibility of your energy storage system.
Suppose you're considering installing solar panels to help prevent electricity outages in your home. In that case, you should know that a solar energy system installed without a battery will not continue to produce electricity during an outage, even during the height of a sunny day. There are two main reasons for this:
First, the output of the solar panels on your roof can vary minute by minute throughout the day. While this doesn't matter when also connected to the grid, if you were to try to power your home straight from solar panels during an outage without a battery, these slight fluctuations in electricity supply would damage electrical equipment and wiring in your home.
But the primary reason solar panels shut off during an outage is for the safety of utility line workers. During an outage, utilities send repair crews throughout their service territory to try to restore electrical service as quickly as possible. If solar still produces electricity during an outage, those panels could feed electricity onto the grid, creating a dangerous situation for transmission workers who expect to work on de-energized wires. For that reason, solar inverters are constantly checking to see if the grid is up and running and will shut down the solar panels' production if they can't detect the grid.
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