Growing weed takes a lot of power, especially with an indoor setup. This can leave growers with hefty utility bills that eat into profits. Often, hot lights and HVAC systems are at odds trying to keep the temperature just right. Though these competing forces are the biggest factor in a grower’s energy bill, there are other factors we can look at in order to reduce the amount of electricity your operation uses.
Nick Earls and Jacob Policzer of The Cannabis Conservancy, an organization whose mission is to improve the efficiency of cannabis grow operations, have provided some tips on doing just that. The tips below will help you conserve electricity and save on your energy overhead.
1. Know How Much You Use
This may seem obvious, but you can’t know if you’re conserving energy if you don’t know how much energy you use to begin with. However, there’s a lot more to it than just looking at your energy bill. You need to do an actual audit, which means getting an idea of how much energy each piece of gear uses.
For lights, you can just multiply the wattage of your bulbs by the duration of their use. Once you have that figure, you can deduct it from your energy bill to determine an approximate consumption level for your HVAC and other environmental systems.
You may also be able to get a free energy audit from your energy provider. In legal states, they tend to treat cannabis businesses just as they would any other business.
2. Photons and Integrals
What we’re talking about here is referred to as PPFD (photosynthetic photon flux density) and DLI (daily light integral). These two factors measure the number of visible light photons your plants are getting per second (PPFD), and the amount of light the plants get per day (DLI).
Once you know these figures, you can start to pinpoint the amount of light each plant is getting, and then trim where necessary to ensure efficiency. In other words, if you know your plants are getting what they need in 16 hours when you’ve been lighting for 18 hours, you may be able to cut that usage down, which could dramatically lower your energy costs.
If you’re running a greenhouse, you can use these numbers to determine how much, if any, supplemental lighting is needed.
3. Check your VPD Levels
Just as knowing PPFD and DLI can help you pinpoint your Goldilox lighting zone, VPD can help you zero in on the optimum temperature for your plants, and potentially save you on climate control costs. Vapor pressure deficit (VPD) measures evaporation and is basically the contrast between air temperature and relative humidity. This number can be used to help you find the best conditions for maximum photosynthesis efficiency.
Policzer points out that this information will help you more closely match the outside temperatures so that your HVAC systems endure less stress. For example, this will help growers run a little warmer in the summer and cooler in the winter while still maintaining optimum photosynthesis.
4. Use Integrated Climate Control
Your climate control system is the heart of your operation, and having all of the different components talking to one another and running in synchronized harmony is essential to tightening up efficiency.
Earls explains how, for instance, someone may inject CO2 into the system based on the PPM reading, but they don’t realize that the exhaust fan of the cooling system is also injecting CO2, resulting in wasted resources. He also points out that roof vents should be tied to the system because cooling systems can cause them to remain open excessively, wasting heat.
These issues can be minimized if not eliminated by using an integrated climate control system. Integrated systems ensure that each step in the system is communicating data to the others so that everything runs at its most efficient level.
5. Use Variable-Control Equipment
We’re mainly talking about lights, watering systems, and fans here, as even the most basic thermostat is, by definition, a variable control for your HVAC system. The general principle is that with variable controls you can add just as much as you need of any environmental control. For example, if you have auto-timers on your lights, that’s great, but auto-timers and a dimmer system can ensure that your bulbs aren’t working harder than they need to be and wasting heat and electricity. Other examples of variable control would be fan speeds, and water pressure levels.
6. Stagger “On” Times
There are a couple of things at work here. The basic idea is that you don’t want all of your equipment running at once if it doesn’t need to be. As an example, say you have a climate controlled room. If you turn the full A/C system on to cool it down, it will cool down quickly and turn off, but you’ve used “peak” energy to achieve climate control. An alternative would be to just have the fans kick on, or the vents open up first to see if the optimum temperature can be reached before you have to turn the HVAC cooling system on. This way you only use as much energy as you actually need to maintain proper climate conditions.
A similar reduction of “peak” wattage can be achieved with lighting. By staggering your lighting banks, you limit the total wattage being used at any given time. So, if you have 300 lamps on for 18 hours, you’re using a huge amount of power for that amount of time. Contrary to what you might think, the six hours of non-use doesn’t really mitigate that at all. A better approach would be to arrange your grow room so that you can stagger your lighting to four-hour shifts, that way you can have a smaller number of bulbs running 24 hours a day. This will reduce your “peak” usage.
Reducing peak usage is important because many energy companies bill based on peak usage. The idea is that if you use a peak amount of 25kw, but you average only 15kw, the energy company charges you at the peak rate for those hours. The goal of staggering is to reduce your peak value so that the overall bill is calculated closer to the average rate.
7. Use Energy-Efficient Fans
This, again, might seem like a no-brainer, but just in case, keep this principle in mind. What you want is the smallest motor possible driving the largest blade radius possible. If you choose a large diameter fan with a ventilation efficiency factor above 15, you should be golden.
8. Level-Up Your Insulation
Another obvious principle of energy efficiency is insulation. Whether you’re trying to keep heat out or in, the insulation in your greenhouse or indoor setup can make a huge difference in the amount of energy it takes to accomplish that. Pay special attention to insulating the pipes of the irrigation system, and be sure to use plenty of weather stripping on windows, doors, vents, and fans to ensure that your HVAC system is only working as hard as it has to be.
9. Remember Your Roots
Happy roots equal happy plants. Therefore, if you can focus your heating efforts on the roots, the need for a higher ambient temperature decreases. Heating systems in the beds of the plants will give the plants the warmth they need at the root, thus allowing for a cooler room temperature. This can be especially helpful in cold-climate greenhouses.
10. Stay Local
If you choose strains that traditionally do well in the climate in which you’re growing, the less you will need to control that climate in order to keep them happy. The less you need to control that climate, the lower your energy bill – and your impact on the climate at large – will be.