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The key characteristics of a battery are the power output, usable capacity and efficiency with which it stores and discharges electricity. Other characteristics, like the chemistry of the battery, help to determine how effective it is at storing electricity.

Warranties are an indication of the overall quality of the battery. Look for a high number of cycles, a high percentage of end-of-life usable capacity, and a large number of years warrantied.

The physical characteristics of a battery help determine whether you'll need an entire garage of batteries or a wall-mounted, radiator-size battery. Beyond just storing energy, batteries have a number of additional traits, such as being able to easily scale in size or to provide power if the grid goes down.

Organizations like the International Electrotechnical Commission (IEC) and Underwriters Laboratories (UL) create national and international standards for energy storage systems to ensure any products on the market meet certain specifications for safety and reliability reasons.