While making a decision about the required size of the power inverter, it is very essential to know the difference between continuous and peak power output. The continuous load is the wattage at which the inverter runs. The peak load is the starting load that is necessary to get the device running. Almost all the inverters have a peak wattage twice to its continuous wattage. If you have a fridge with a start up load of 15 amps and a continuous load of 5 amps, the peak surge rating can be calculated as follows: 5 amps X 120 volts = 600 watts continuous load 15 amps * 120 volts = 1800 watts starting load In this scenario, you will have to look for an inverter with a peak surge rating that is greater than 1800 watts.