Capacity and Power Measured in kilowatt hours (kWh), capacity is the amount of energy a battery can store over time. More literally, capacity is how much energy (measured in kW) a battery can store over time. The more capacity a battery has, the more power it can store. Power is how much energy a battery can provide at a given moment. A battery with both a high capacity and high power can run a large system for several hours; a battery with low capacity and high power can run a large system but only for a short time. Efficiency Efficiency is the amount of energy used compared to the amount of energy it took to store said energy. Batteries require power to charge and efficiency compares the energy taken to charge a battery with the amount of energy that the charged battery produces. The higher the efficiency, the more cost-effective the battery. Manufacturer This may not be a component most would consider, but it is something to pay attention to. As with other technology, there are both trusted brands and start-up brands. A trusted brand comes with known flaws and benefits; a start-up brand can perhaps have better technology, but can also have yet unknown technological issues. Depending on your system needs, you may decide to go with a well- reviewed company or one that is brand new to the market. View our Free Presentation to learn how to bring old batteries back to life again