What size inverter should I buy?

The size you pick depends on the watts (or amps) of the device you want to power (find the power consumption by referring to the specification plate on the appliance or tool). We suggest purchasing a model that is at least 10 to 20 percent greater than your heaviest load.

You want to power a computer with a 17-inch display, some lights, and a radio, among other devices.

Power supply for a computer: 300 watts
2 – 60 Watt lights: 120 Watts
Radio: 10 Watts
Required Total: 430 Watts

For this purpose, a 500 W inverter is the very minimum; nevertheless, you should consider purchasing a larger one, since there may surely come a time when you wish you had purchased one. In this scenario, you could elect to run a fan while you work or let the kids watch television.

Establish Continuous Load and Starting (Peak) Load: You must determine how much power your tool or appliance (or combination of tools or appliances that you would use simultaneously) takes to start up (starting load) and how much power it requires to operate continuously (continuous load) (continuous load).

The distinction between “continuous-2000 watts” and “peak surge-4,000 watts” refers to the fact that some appliances or equipment, such as those with a motor, need an initial burst of electricity to start up (“starting load” or “peak load”). Once started, the instrument or appliance continues to function using less energy (“continuous load”)

Helpful formulas:

In order to convert amps to watts:

Multiply: AMPS X 120 (AC voltage) = WATTS
This formula provides a close estimate of the appliance’s continuous load.

To Calculate estimated Startup Load:

WATTS multiplied by two equals the starting load.
This formula produces a near estimate of the appliance’s initial load, while some may need an even higher starting load. NOTA: Induction motors, such as those used in air conditioners, refrigerators, freezers, and pumps, may experience a start-up surge of three to seven times their continuous rating.

Typically, the starting load of the appliance or power equipment decides whether or not an inverter can power it.

For instance, a freezer has a constant load of 4 amps and a starting load of 12 amps:

4 amps x 120 volts equals 480 continuous watts
12 amps x 120 volts equals a starting load of 1440 watts

You would need an inverter with a peak-surge rating of over 1,440 watts.

CONVERSION OF AC WATTS TO DC AMPS:

AC Watts subtracted by 12 x 1.1 equals DC Amps (this is the size vehicle alternator you would need to keep up with a specific load; for example, to keep up with a continuous draw of 1000 watts, you would need a 91 amp alternator)