Standard 12v models top out around 3000w (24v/48v ~ 4000w). To proceed: Upgrade to a higher-voltage system (24 V/48 V) for a larger inverter. Use the dropdown to add common devices—or enter your. . We created a comprehensive inverter size chart to help you select the correct inverter to power your appliances. Minimum. . You can use the following formula to determine the size: Volts * Amps = watts or Watts / Volts = amps 1250-watt example: 1250 / 120 Vac = 10. 41 amps AC (typical number found on equipment) or 1250 / 12 Vdc = 104. 1 amps DC (battery drain per hour) Here is an example: First, you need to determine what. . An inverter is a device that turns the power from a 12 volt DC battery, like the one in your car or truck, into the 120 volt AC power that runs all of the electronics in your house. Introduction: Why Inverter. .