A solar energy system produces electricity whenever sunlight hit your panels. So when it is overly cloudy or nighttime, the solar modules are not producing anything.

Also, when you are connected to the grid (as with grid-tied systems) - when the grid goes down, your system goes down. This is where the battery backup comes in.

If your system is off-grid, you must have a battery bank:

Since you need electricity when it is cloudy and nighttime, and you can't get that electricity from the grid since you are not connected to it. Most off-grid battery banks are designed to provide anywhere from 1-5 days of emergency power during overly cloudy or other adverse conditions.

Grid-tied systems can also have battery backup:

Which is used to provide electricity during emergency situations - such as blackouts. It is perfect for keeping critical electric loads operating until the utility power is restored. This will increase the cost of the system by up to 20%.

The batteries themselves are similar to ordinary car batteries:

They are specifically designed to endure the charging and discharging they'll go though with a solar energy system. Lead-acid batteries are the most common battery used. Flooded lead-acid batteries are often the cheapest, but require some additional maintenance.

When deciding on a battery backup system, an Astralux Solar Expert will work with you to decide the size, type, and loads you'll be backing up.

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