# Why does a 7200 watt AC generator need a 10hp motor? 7200 watt AC generator and it needs to run at 3600 rpm. Factory recommends a 10hp motor to run this generator. Is that just to keep the...

Why does a 7200 watt AC generator need a 10hp motor?

7200 watt AC generator and it needs to run at 3600 rpm. Factory recommends a 10hp motor to run this generator. Is that just to keep the generator running at 3600 rpm or does the generator have more resistance as the draw on the generator increases? Is that why you need that much horsepower to run the generator when its running at full load.

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Would it help you to know that Watt and Horsepower are different measures for the same thing? A watt is a unit of power (energy over time), so is a horsepower (hence the name power). According to the calculator in my computer: 7200watts = 9.655 Horsepower. That's why they recommend a 10 horsepower engine on the generator. 10 Horsepower is equal to just over 7200 watts.

It should also be noted that since Power is just energy over time, you need to consider that Energy cannot be created or destroyed, it can only change forms. A generator changes the Chemical energy in Gasoline into Heat and kinetic energy, and then changes the kinetic energy into Electrical energy at a rate equal to the power of 7200 watts, or 10 horsepower.