Inverter Calculator

About

Continuous / Surge Power

Power equipment and appliances which operate with motors or tubes require an initial surge of power to get them up and running. This power surge is referred to as the "starting load" or "peak load." (By comparison, electrical devices such as standard light bulbs do not require a large starting load.) Once the equipment or appliance has been powered up, it settles down to a slower pace and requires far less electrical power to operate. This lower power requirement is referred to as the "continuous load."

In order to ensure that the capacity of your power inverter is sufficient to meet the required start up load, you must first determine the power consumption of the equipment or appliance you plan to operate. Power consumption is rated either in wattage or amperes, and information regarding the required "watts" or "amps" generally is stamped or printed on most appliances and equipment. If this information is not indicated on the appliance or equipment, check the owner’s manual. Contact the appliance or equipment manufacturer to determine if the device you are using (TV’s, battery charger, computer, etc.) is compatible with a modified sine wave. If not then you should purchase an inverter that has a pure sine wave or true sine wave output.

If the power consumption is rated in amps, multiply the number of amps by 120 (AC voltage) to determine the comparable wattage rating. Induction motors may require 2 to 6 times their wattage rating to start up. 

Battery Info

To calculate the Ah of the battery, first determine its "reserve minutes" rating. (Deep cycle marine batteries generally have the highest reserve minute ratings). This rating typically is marked on the battery along with the "Cold Cranking Amps" (CCA) rating. Multiply the reserve minutes rating of the battery by 0.3 to determine the battery approximate Ah rating. A battery with a reserve minutes rating of 166 has an Ah rating of 49.8.

To estimate the maximum battery current the inverter will require to run a piece of equipment or appliance, divide its continuous load wattage requirement by 10.