There are a lot of factors that go into purchasing a grow light. Most people start out by searching for a light with a specific power rating. As you try to narrow it down, you realize that there are dozens of other factors to consider. At first, it might seem as if qualities like price, heat, spectrum, and size are only vaguely connected to each other. At the end of the day, each of these metrics help to calculate the same thing – efficiency.
What is Efficiency?
People break efficiency down into all kinds of subcategories. The most power-efficient bulbs keep your electricity cost low. The more thermos-efficient lights produce less heat. For now, let’s keep it simple. The formula for efficiency is simply input over output.
The purpose of a grow light is to facilitate photosynthesis in our plants. In order to do that, the light needs to be supplied with electricity. Whichever grow light can facilitate the most photosynthesis with the least amount of electricity will be considered the most efficient. Sounds simple, right? On paper, it might be. But if you’re trying to plan out your grow room, you’ll need to understand all of the potential sources of loss.
From Electricity to Photosynthesis
Although it would make our lives a lot easier, plants cannot run on electricity. It takes five steps for electricity to be converted into something your plants can use, and each of these steps results in a little bit of loss. To understand where we’re losing energy, we’ll go through this process step by step.
Step 1: Transformation
As soon as you plug your grow light into an electrical outlet, electricity flows through the wire and into the lights controller. In North America, our power is transmitted as a 110-volt AC signal. This harsh electrical signal would destroy the delicate LEDs in seconds, so a device called an “LED Driver” or “Bridge Rectifier” transforms it. Imagine trying to drink from a faucet with high water pressure. You wouldn’t want to put your mouth directly on the tap. Instead, you fill up a glass, only taking a sip once the water has settled down. Converting AC to DC is a very similar process. Instead of a glass, the electricity passes through a coil, some diodes, and a capacitor. This is where the biggest loss of power occurs. 90% of the AC electricity is successfully converted into DC, but the rest of it is converted to heat and magnetic interference.
Step 2: Distribution
Your LED grow light is composed of dozens, if not hundreds of individual LEDs. In many cases, there will even be multiple types of LEDs each of which produce a different part of the lighting spectrum. Your single DC power source now needs to travel through a network resistors, wires and switches to reach their destination. Each of these components tends to get a little warm, resulting in another small loss of energy.
Step 3: Conversion
Up until now, electricity has been flowing through conductors, with small amounts of it being converted into other energy forms along the way. Once it hit’s the LED, all of the electrical energy will be converted into another form: light. Electrons are able to flow so easily through a conductor because they have a very specific charge. The LED acts almost like a pool, catching these electrons and slowing them down. The electron immediately loses a large portion of its energy as heat, and enters a lower power state known as a photon – a unit of light.
Step 4: Positioning
LEDs are very effective at creating light, but they are not very effective at aiming it. The photons leave the LED in every direction at once, with most of it facing away from your plants. This is why most grow lights have lenses and reflectors. Lenses are able to bend the light, directing it in a predetermined position. Although lenses are very accurate at directing light, there is always some that is reflected rather than refracted. Once again, a small adjustment has resulted in a loss of usable energy.
It doesn’t matter how many lenses and reflectors you have, you’re never going to get 100% of your light to hit your plants. Just because it’s not perfect, doesn’t mean it can’t be optimized. Pay careful attention to how your light is designed to be used, and ensure you’re following the guidelines. Even the best grow lights on the market will perform poorly when use improperly.
Step 5: Absorption
Finally, the process has come to an end. Our plants are happily soaking up the rays, performing a little energy conversion of their own. Unfortunately, they’re not necessarily soaking up all the rays. As we’ve discussed here, different wave lengths of light produce varying levels of photosynthesis. So it’s not just about getting light to your plant, it’s about getting the correct light.
What Does This Mean for You?
After reading this, you might feel like energy is going everywhere except your plants. Luckily, there are simple ways that you can mitigate every single source of energy loss.
- Purchase a High-Quality Grow Light
When manufacturers use high quality components, power loss from internal circuits is negligible. This is obvious when you compare the specifications of a cheap LED grow light against a high-end model. In this case, the power draw is cut in half when the proper components are used.
- Use the Right Metrics
Often, LED grow light manufacturers advertise the ‘performance’ of their light with the power draw (watts.) By this logic, auto manufacturers could start claiming that they have the most fuel-efficient vehicle because they have the largest fuel tank. In fact, you can’t even compare grow lights based on the amount of light they produce. The only effective way to rate these lights is with three different variables. PAR, PPF, and PPFD. These metrics tell how much usable light is produced, how this changes over time, and the distance that this light can cover. If you’re not familiar with these terms, make sure you check out our explanation here.
- Position Your Lights Correctly
You could have the most advanced grow light in the world. But if you don’t set it up properly, your results will be disappointing. Each light is designed to cover a certain area. You’ll have to position the light at a certain height, and ensure that the coverage is adequate for the number of plants you have and their cycle. Coverage is determined primarily by the type of LED lens your lights are using, and most manufacturers provide recommended heights.
- Use the Right Spectrum
Some wavelengths of light are easier for LEDs to produce, and some are more efficient at producing photosynthesis. If you want an efficient grow, you’ll need to ensure that your LED grow lights are producing the correct spectrum of light. We’ve explained how your light spectrum affects photosynthesis in this post, but it’s important to remember that the type of light you use will also depend on which cycle of life your plant is in.
Although grow lights are complicated in nature, ensuring you set up your lights in accordance with these factors can ensure you have an efficient grow. If you’re not sure where to start, our ultimate buyers guide to LED Grow Lights is a great place to start!