MH vs HPS Grow Lights & HPS vs LED Lights for Marijuana

All New Homegrown PotCast
December 09, 2020

When it comes to growing cannabis, choosing the best marijuana grow lights is one of the first steps, but how do you know which grow lights are right for you? Let’s take a look at some of the options and decisions you will face when picking the best cannabis grow lights. This week’s PotCast episode is all about lights!

MH vs HPS Grow Lights

MH and HPS lights have been used for cannabis as staple grow lights in many commercial setups and homegrown setups.

MH, or metal halide, are light bulbs using an electrical arc that goes through a gaseous mix, creating light. Metal halide, or MH, use metal and halogen to create a unique color temperature of light. MH lamps will normally be found using metals that have been mixed with iodine or bromine. Depending on the specific metals used will determine the exact color of light temperature emitted. Now these individual bulbs, which are made up of an inner tube and outer tube, the inner tube having the arc and metals within it, last around 15 to 20 thousand hours. With the average 1000 watt MH bulb costing around $20 a bulb, that’s not a bad deal.

HPS on the other hand, or High-Pressure Sodium lights, cost around $53 for Hortilux bulbs, which are considered the better bulbs for growing cannabis. Now, these lights do, however, have some pros that may make them a good counterpart to MH, as MH is generally used in commercial farms for vegging plants, whereas HPS tends to be used for flowering stages of development. So what are HPS lights? They are light bulbs, consisting of tubes just like MH lights, with an inner tube and outer tube. The arc tube, or inner tube, has a higher pressure inside of its tube to create a more efficient light, which then the arc heats up the mercury. The mercury vapor then gives off light, which gives the light a bluish hue.

Now once the lamp heats the sodium is last to vaporize which strikes an arc at 240 degrees Celsius or 464 degrees. The sodium then mixes with impurities to create more white light, mercury adds a blue spectrum to the pure yellow sodium which creates an orange almost yellowish light that gives a nice blue spectrum of wavelengths.

Now, why is that blue spectrum important? That blue spectrum has been found in many strains of cannabis, not all as many plants have ancestral lines from different parts of the world that grow better in different wavelengths of light, but the blue spectrum has been found in many plants to increase THC and Terpene levels by upwards of 4%. For many growers, that’s enough to either add HPS to their garden or completely make the swap.

Efficiency, potential THC and Terpene increase, and cost compared to MH put HPS just slightly above MH for the flowering stage, but below MH for the vegetative growth phase.

Find out which comes out on top overall by listening to the PotCast above!

HPS vs LED Grow Lights

LEDs are Light Emitting Diodes that are semiconductor light sources that combine P-type semiconductor with an N-type semiconductor. This combination applies a sufficient forward voltage that will cause the electrons and holes to recombine at the P-N junction which releases energy in the form of light. This causes an efficient light source that wastes little electricity and delivers efficient light with less heat output than any light compared to LEDs.

The average LED lasts for 50,000 to 100,000 hours depending on the manufacturer, bulb, or fixture. The average LED fixture for a 1000 watt light cost around $800 to 1000 dollars or more. Since we compared the top end lights for HPS, let’s compare the imprint of one Eye Hortilux bulb to the Black Dog Phytomax-2 1000watt light.

Now, the HPS bulb only puts out max PAR within left to right or front to back fashion, depending on how you hang your fixture and not a square imprint. This means to cover a true 7×7 foot space we’ll need to do some math, as a 24 sq ft imprint is relatively a 2x2x6 foot space in grower terms. So we will need 4 HPS lamps, which will equal $520 roughly. Now we then consider the heat output, height, and cost of fixtures for HPS, as HPS, does require a fixture just like MH.

So, for HPS, the average cost of a 1000 watt fixture is $220 to 300, so let’s say $250 and meet somewhat in the middle. Your $520 is now $1520 as you just added $1000 of additional fixtures to cover an 8×8 imprint. You’re also now increasing electricity pull, costs, and heat output from 4 1000 watt lamps to get roughly 1300 to 2500 PAR output per 2×2 space.

If you would like to find out the overall conclusion to this debate, scroll back up to the top of the page and hit play on the PotCast episode, and find the best lights for your grow!

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