A 12V 150ah battery can store 1800 watts so a 2000 watt inverter is the right size. Inverter capacity is measured in watts. Battery sizes are measured in amp hours, so you need to find out how many watts a. Pairing a right size capacity battery for an inverter can be a bit confusing for most the beginners So I have made it easy for you, use the calculator below to calculate the battery size for 200 watt, 300 watt, 500 watt, 1000 watt, 2000 watt, 3000 watt, 5000-watt inverter Failed to calculate field. The number of batteries you need depends on three factors: your inverter size, how much power you actually use, and how long you need to run. This tool reduces guesswork and gives reliable results that support.