When talking about electricity, and electrical power (like when you’re ordering a generator), it’s important to listen to what your electrician (or gaffer or caterer or whomever) says. Duh, right?

Personally, this is one of those subjects that I had a very hard time wrapping my head around. So, for another installment of basic information (and an excuse for me to educate myself) I’m writing a primer on electricity.

There are four phrases you’ll hear in the electricity discussion: amps, watts, volts, and ohms. The most often used analogy is to that of a plumbing system.

Volts can be seen as the water pressure in the tank or reservoir.

The electrical current, which is measured in amps, is the equivalent of the water flow rate. In other words, amps are a measurement of how much electricity flows past a point in one second. You can see why the plumbing analogy is used so often, as “current” is used interchangeably here.

The water pressure can be increased (like when you put your thumb over the end of a hose), therefore increasing or decreasing the power of the water stream. Obviously, the current remains the same, but you get more power. This is called “resistance”, and is measured in ohms. Ohms can most easily be defined as the size of the pipe.

So, the power of an electrical system can be figured by a simple equation.

Power = Voltage x Current

Power is measured in Watts. So, Voltage x Amperage = Watts

For a simple example, here is a picture of one of our 3000W generators:
(insert photo here)
As you can see in the picture, the voltage is 120V. The two plugs on the left put out amperage (current) of 20A. The one on the right is 23.3A.

120V x 20A = 2400W

-and-

120V x 23.3A = 2796W

Let’s say you’re running this 3000W generator on a night shoot. You have one of our double-worklights plugged in, which takes about 1000W. You also have a stinger with a cube tap, and two space heaters plugged into it. The space heaters use minimal voltage. When your gaffer needs to plug in his 1K Fresnel, you’ll have plenty of wattage to spare.

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