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First off, let’s start with the simple formula for power usage calculation. I know math sucks, especially algebra (even simple stuff), but look at this way: remember in high school when you said “I’m never gonna use this shit?” Well, I’d say there is no more fitting or ironic a place to use those mostly useless skills than for growing cannabis.
Voltage x Amperes = Watts
Let’s assume a few constants for those of us in the U.S. Every house in the U.S. has a line voltage on any outlet of 120 Volts, as a rule of thumb. Some non-grounded devices only use 110, but that’s not for our discussion. Let’s just stick to 120 Volts. So let’s use this in a calculation for an example for say, a vacuum cleaner.
Mine, as do most, use 12 amperes, or amps for short. So, 120v x 12a = 1440 watts. Yup, 1440 watts is what a sweeper uses on average. But WTF is a watt?
A watt is a measure of the amount of energy used. For the power company, it is often rated as Kwh. This is a Kilowatt per hour, or 1000 watts per hour. Now this is where it gets a little weird. People often ask, so how many Kwh does a 60 watt light bulb use per hour? It uses 60 watts per hour. That’s it. So in this case, we just do another simple formula and move the decimal place back.
60w /1000 = .06 Kwh.
Why is this important? How much are your lights using? USED watts, for you HID people. For HID people, just because the bulb is, say, rated at 600 watts, you might actually be using 640 watts. Check your ballast for that info. So, if you are consuming 640 watts for you 600 watt HPS, you are using .64 Kwh. Now you can calculate how much your gear will run as every device you use that plugs into an outlet will have a power consumption rating on it. Fans, lights, etc. All of it. So, let’s say you are using the following as an example.
2 400w ventilation fans
1 1040 watt HPS (total use)
You are using 1.44 Kwh there. But what about your bubblers and things that don’t have a wattage rating?
Ah ha! Well, on the power source (the black box that plugs into the outlet), you will see a rating on there expressed this way.
INPUT 9v, 0.5a. This means it is 9 volts and .5 amps. So using our first formula;
9v x .5a = 4.5 watts. So, let’s say you have 4 of these little guys running. Let’s add that to the total!
2 400w ventilation fans =800w
1 1040 watt HPS (total use) =1040w
2 4.5 watt bubblers = 9w
Total watts = 1849 watt or 1.849 Kwh.
Power companies charge by the Kwh, as I said above. Now, from looking at your bill, you can see how much you are charged per Kwh. The national average is 12 cents per Kwh. So, the hypothetic setup using 1.849 Kwh multiplied by $.12 = $.22 dollars (or 22 cents per hour) to run. If you run this ALL OF THIS 24 hrs a day for a 31 day month, you are paying $ 165.08 a moth to run it all. Compare that to you bill of current usage and decide how paranoid you are. Also remember that cutting down how long you have stuff on with save a lot of power. If you only run the equipment 18 hrs a day, then instead of 1.849Kwh x 24hrs x 31days = total Kwh use, you would calculate 1.849Kwh x 18hrs x 31 days.
Now that we understand a few of these basics, let go to safety using it. Safety is VERY important. And I’m not talking about getting the shit shocked out of you if you touch a live wire (which is a bad idea too obviously) but rather about fire hazard. An extension cord not able to handle the load you are forcing it to can over heat. Once this happens, the insulation around the cord can melt or burn causing a short and a fire. Just because you have a breaker on the circuit doesn’t mean it will flip and protect you. What if the breaker is faulty? What if the amp rating on the breaker is large enough that it won’t flip because it was in a circuit that can also handle big power items like dishwashers or things? A lot of us in this country live in old home where wire has been installed, patched, modified, and reworked over the last fifty + years, sometime done by shitty electricians. In my place, which was built in the late 1800’s early 1900’s, there are still natural gas outlets built into the walls for old gas lighting! Now the place is in great shape and has been well maintained over the last 100 years. You’d never know it was that old if you went on a tour with me. But, it was converted from gas to electric prolly sometime in the 20’s. And there is a scary amount of original wiring in the place. It works, and it’s nothing to be afraid of, just something to keep in mind. Mine has been modernized over the years to modern breaker boxes and what not for safety, but some of those outlets are still original. Scary. As a rule of thumb there I figure if the outlet doesn’t have a ground, bad idea to use it for a show’s power. If it is grounded (the third round prong hole) and you are still not convinced, open up the outlet and see, JUST FLIP THE BREAKER ON THAT CIRCUIT OFF BEFORE YOU DO! If the leads are insulated with what looks like braided cloth, it’s old. But like I said, just because its old doesn’t mean it’s bad and automatically unsafe or half this countries’ homes would have gone up in flames already! Just bear it in mind.
So that takes care of the power supply. But now you got to get that power to your equipment. Power strips are ok, BUT READ THE LABELS! All extension cords, power strips, etc will have on the label the amount of power they can handle. It will often be expressed simply in amps. So what do you do? As mentioned above pretty much every home in the U.S. uses 120 Volts. So, if you see a cord that says 12 amps, then 120v x 12a =1440 watts MAXIMUM POWER. I would undercut this to stay on the safe side. I would get a more heavy duty line that can handle more juice than you will be putting through it. Just think your setup through. Plan every connection and read every label of every cord you buy. Do your math. And you should be fine.
On a final note, some setups will require wiring things directly in. In that case, use wire caps to connect wires, not electrical tape, and place all connections in junction boxed. I won’t delve into this too far as it is more advanced than most subsistence growers will need to do, but if anyone has any additional questions about wiring, ask away and I welcome other members to help answer these questions and to point out errors in my post. Just remember, do your math and be safe!
For more questions and to look up how much common household items use, go here. It is a great source of info!