Plasma grow lights work by exciting a substance with microwaves, until it heats up enough that it turns into plasma and emits light. In school many of us learned of 3 phases of matter: solid, liquid and gas; plasma is another phase of matter even more energetic than gas.
Intensity of Plasma vs. LED Grow Lights
Like LEDs, plasma grow lights can come in a wide range of intensities. Some are bright enough to grow plants well, others aren’t.
Spectrum of Plasma vs. LED Grow Lights
Plasma systems create a fairly even spread of light across much of the visible spectrum, but no practical system can cover both the red and blue end of the spectrum equally. Plasma lights tend to either be more blue-weighted (like MH lights) or red-weighted (like HPS lights). Like dual-arc HID bulbs, some plasma lights combine both a blue and red bulb into one to cover both colors plants like. Just like dual-arc bulbs, this ends up doubling the amount of yellow light being created that plants cannot use efficiently.
LEDs allow a grow light to be created by cherry-picking just the colors plants want and leaving out the colors that are wasteful.
Lifespan of Plasma vs. LED Grow Lights
Plasma bulbs vary tremendously in how long they last, but due to the extreme temperatures used to create the glow inside the bulb, the plasma literally “eats into” the bulb and causes it to degrade, usually in 6-18 months. LED grow lights last 10-20 times longer.
Efficiency of Plasma vs. LED Grow Lights
Plasma lights are even more efficient at creating light than HIDs, and rival LEDs in efficiency for general photon output. LED grow lights can still be more efficient for growing plants because they allow complete control over spectral output, so energy isn’t wasted creating light plants can’t use efficiently.