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Get Wired: 120 Volts vs 240 Volts for your Grow Room


One of the most common misconceptions regarding an indoor garden’s wiring is that a grower can save up to 50% on the electric bill by switching from 120 volts to 240 volts.

The voltage at which an indoor garden is operated has nothing to do with the cost of electrical usage. Electric companies charge their customers for the amount of wattage used. This is usually marked on the electric bill as total kWh (kilowatt hours) usage.

A kilowatt hour is a unit of measurement that represents 1000 watts being used for one hour of time. This is how most electric companies bill the user and how growers can compare rates. The most important fact to remember is that the user is always charged for the amount of wattage consumed, not volts or amps.

The most important fact to remember is that the user is always charged for the amount of wattage consumed, not volts or amps.

A room wired for 120 volts would usually consist of three wires: a hot wire (120 volts), a neutral wire, and a ground wire. A room wired for 240 volts would usually consist of four wires: two hot wires (120 volts each, totaling 240 volts), a neutral wire, and a ground wire.

The exception to this would be some older homes where the ground wire wouldn’t apply. In this case, the 120 volt would have two wires (a hot wire and a neutral wire) and the 240 volt would have three wires (two hot wires and the neutral wire).

If a grower is serious about deciding whether to operate the grow room on 240 volts or 120 volts, they should first get an understanding of how volts, watts, and amps affect each other. The current (amperage or amps) is always equal to the power (wattage or watts) divided by the voltage (volts). In other words, amps = watts/volts. 

Let’s use an example to see how 120 volts versus 240 volts affects the equation.

The example grow room has 4000 watts of electrical power requirements. At 120 volts, the garden would require 33.3 amps (4000W/120V = 33.3A). If that same garden was wired for 240 volts, it would require 16.66 amps (4000W/240V = 16.66A).

The real benefit of operating a grow room at 240 volts is that it allows the grower to operate more lights (wattage) on the given amperage. Amperage is the limiting factor for many indoor horticulturists, especially growers who have the home’s electrical usage and garden’s electrical usage on the same electric panel.

As you can see from the example, there are no financial savings by operating a garden at 240 volts versus 120 volts because the voltage does not affect the wattage being consumed. It is the wattage (or electrical usage) that the grower is charged for and this number will not change based on the current (amps) or voltage being used.

Although there are no financial savings, the big advantage of freeing addition amperage for other uses justifies many growers opting for a 240 volt garden over a 120 volt garden. After all, by doubling the voltage, a grower can double the amount of lights being operated and, therefore, double the entire size of the indoor garden.

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Here’s a lesson in electricity for you to better understand your grow room.
Last modified on Thursday, 10 October 2013 19:22

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