One of the things that most people underestimate is how much power it takes to grow a crop from start to finish. Let’s just break this down into bite sized chunks of lighting, nutrients (whether hand-fed, through emitters, or any other way), air flow, and heating and cooling.
Why do you separate air flow from heating and cooling when they are intertwined? Well think about fans for instance. They can be for the plants or exhaust or intake of fresh air, so filtration is recommended; some people have a strong fan blowing on the top of their reservoirs to keep the water temp down! If you have a sealed room environment, then you have circulation fans and could even have fans taking hot air by the ceiling and running down to ground level to create convection loops to even out the overall temperature in the room. One of the things you’ll find early on is that without enough planning and thought, you can very easily have an uneven room with hot and cold spots and even different microclimates where one spot is dry and the other too damp. Good air flow is key to success in the grow room.
Now let’s take a look at HVAC (aka Heating, Ventilation, and Air Conditioning). You need to know some simple facts: they use a lot of power, AC dries the air out to cool it, and heating air lowers the humidity levels, so you need to have a humidifier if you live in a naturally dry climate area and a dehumidifier if it gets too damp. By having the proper gear to control the environmental variables you have the ability to create an ideal space for your plant success.
Moving on to lighting. People have been growing indoors for centuries at this point and the one constant that can’t be ignored is proper lighting. You need the right bandwidths of light and intensity to get the desired results and that will consume power as well. To get back on point let’s take an example of a 630 watt LED grow light like the Spectrum King LED SK602. It draws 630 watts of power to be fully lit and give more light than a conventional 1,000 watt bulb with a better spectrum. So you save power per light and create less heat, but you are still consuming power. In this example 630 watts = 0.63 kWh (a kilowatt is 1,000 watts and power is measured in kilowatt hours) so each light that is on for 12 hours at full power draws 7.56 kWh (0.63 x 12 = 7.56). That is a per fixture power draw which may seem like a lot but keep in mind vs a 1,000 watt bulb which actually pulls closer to 1,070 watts each that number would be 12.84 kWh. Now if you’re running a handful or even many more lights that difference adds up quickly.
Every device you connect to power has a power draw typically rated in watts. You’ll need to check all of your selected components and see what the manufacturer’s claims are, and in some cases buy a kilowatt meter and see for yourself what they actually use. Once you know how much power a device uses you can then calculate how many kilowatt hours a day it will use by how much time it will be run.
Power bills can be muddled and confusing, so some find the best way to calculate what you actually pay per kilowatt hour is to see how many kilowatt hours your power provider charged you for and then divide your bill total by that number. That way, you get what you actually pay with all fees and charges. Once you have calculated that kWh charge, you simply add up all the totals you’ve worked out per fixture per day and multiply that number by the kWh rate and there is your daily total. At that point you can figure out your monthly and annual totals and know what your bill should be. If the numbers don’t match, just go over your logged devices and see if you missed anything. If you have tiered billing it gets a bit more complex but that just means seeing how many kWh per tier you were charged for and what the rates are for that tier and each subsequent tier.
To sum it up, taking the time to review what your actual power usage is by logging all of your devices to be used and how often they should be used really helps you budget and know what you are paying—and what you will be paying if you expand. Knowing how much power you use is a great way to keep your operational costs in check.