To determine the size of a solar battery, estimate your home's daily power consumption in kWh and use the Solar Battery Size Calculator to plug in your average daily energy usage, decide on the number of backup days you want, and select your battery's depth. For a 2kW solar system, the number of batteries required depends on several variables, such as daily energy production, desired backup autonomy, and the type of battery chosen. Let's break it down step by step so you can easily calculate the right number of batteries for your 2kW solar system. Enter your daily load, autonomy requirement, and battery chemistry to get battery count, inverter size, and estimated system cost. How to Choose the Best Solar Storage Container: A Complete Buying.