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Why upgrade from HPS to LED grow lighting?

If you setup a HPS grow light system correctly it can bevery efficient

An optimised 600W HPS grow light system delivers 1.3 µmol/watt.

HPS is a great low cost technology, proven over years of use and is efficient when setup correctly. So why upgrade from HPS to LED?

Let’s compare the LED vs HPS performance and costs first and see if it makes sense. Then we can look at the really exciting aspects of growing with LEDs.

Growing with HPS is still a great option

Many articles discussing the benefits of LED over HPS do not use an optimised HPS system to compare to. This makes some LED vs HPS comparisons look more impressive than they really are.

In this article we use an optimised HPS system for comparison as follows:

  • Digital ballast (95% efficient)
  • High PAR bulb (Sunmaster, Grow+ Photonic)
  • High quality reflector (Adjust a wing Defender, medium size)
  • An enclosed environment and highly reflective walls (silver mylar)

The efficiency of this system is 1.3 µmols/watt PPFD. This means for every watt of energy consumed 1.3 µmols of PAR light will reach the plant canopy.

This is a very good efficiency result and only a few LED systems on the market today are better than an optimised HPS system.

Only a few LED grow lights are more efficiency than an optimised HPS grow light

Comparison table of some popular LED grow lights and and optimised 600W HPS grow light system

So, why would you change to a high efficiency LED grow light?


Invest to reduce costs over time

To achieve high efficiency with LEDs manufacturers must use top of the line and expensive components. This means you have to pay over twice as much for a highly efficient LED grow light system than an efficient HPS system. However, by saving 40% on electricity and no replacement bulbs costs you will get payback in just over two years of growing. After that you are saving every further year you grow.

You can pay back the initial investment in a highly efficient LED growlight system in 2 years of growing

The initial purchase cost and running costs combined show a 2 year payback for a highly efficient LED grow light Vs a HPS grow light system


Double your yield in grams per watt

If you weigh your yield of dry herbs and divide by the grow lighting systems power consumed (per hour) you get a number in grams per watt. This number is the best way to benchmark how good a grow light is. Typically the yield from a HPS system will be 0.4 to 0.5 grams per watt. A typical 600W HPS system yield is 640 watts x 0.4grams = 240 grams per grow cycle. With a highly efficient LED system you can double the yield per watt.

A MIGRO 400 LED grow light can deliver twice the yield per watt of a highly efficient HPS system

LED Vs HPS yield result from our UK grow diary

As an example, our grow UK grow diary achieved twice the grams per watt with a MIGRO 400 compared to an optimised 600W HPS system.

So you can grow more with the same power consumption or grow the same with half the power consumed.

LED provides the best growing spectrum for high yield

The HPS spectrum is mostly red and green. Red is good for flowering and green is excellent at penetrating the canopy. The lack of blue at only 3%, even in the ”dual spectrum’ HPS bulb tested, means that the plants

will be prone to stretching. 10-15% blue is necessary to keep the plant growth dense.

The MIGRO Full spectrum LED grow light is closely matched to the spectrum of the Sun.

Spectrum comparison of the Sun, A Full Spectrum MIGRO LED grow light and an dual spectrum HPS grow light


With LED you can tailor the spectrum to get the optimum balance of Blue, Green and Red to match natural daylight. Ideal for healthier plants and higher yields.

The Full Spectrum LED has enough blue light to ensure healthy and dense growth in the flowering stage

The proportions of Blue, Green and Red in the light from the Sun, a Full Spectrum MIGRO LED grow light and a dual spectrum HPS grow light

Reduce power consumption by 40%

Some LED systems outperform an optimised HPS system and achieve much better efficiency. This means you can grow more with the same or smaller footprint. The MIGRO 400 is highly efficient at 2.0 µmols/watt PPFD. Replace a 600W HPS system with a MIGRO 400 LED and the power consumption reduces from 640 watts to 370 watts.

Reduce Heat by 50%

If your grow light system is inefficient it will produce less light and more heat. The additional heat leads requires more ventilation to remove it and can stress and damage plants. In the worst case you may have to stop growing during hot spells or use air conditioning.

The MIGRO 400 LED will produce 50% less heat than the equivalent 600W HPS system. Your plants will be less stressed in warm weather and your fans will run slower and quieter.


Voltage in the grow room

A HPS Bulb is started with the ballast with a voltage between 2500 and 4000 Volts. This is necessary to spark across the gap in the tube and illuminate the gas inside. The voltage then adjusts to the normal operating voltage of the HPS bulb at around 230 Volts.

LED technology has no requirement for a startup voltage and the MIGRO LED grow lights will run at less than 102Vdc in the grow room. A low and safe voltage to have in the grow room around water and plants.

Water protection

It is not possible to insulate the HPS bulb against water splashes as the bulb screws into an open terminal which it is not possible to seal. The requirement to have air circulating and cooling the bulb means it is not possible to seal the HPS fitting against water ingress.

The MIGRO LED is completely water sealed to Ingress Protection (I.P.) rating of 67 which means the light fixture and cables can be submersed in water up to 1M in depth.

HPS thermal image

Thermal image of a HPS bulb shows the surface temperature in excess of 330 Degrees Celcius or 636 Degrees Fahrenheit

The surface temerature of the 600W HPS bulb tested with our thermal imaging camera was in excess of 330 Degrees Celcius or 626 Fahrenheit (the thermal camera range ends at 330 Degrees Celcius so the actual temperature is higher).



MIGRO thermal image

The thermal image of a MIGRO LED grow light at normal operating temperature of only 40 degrees Celcius or 104 Degrees Fahrenheit

The MIGRO LED is passively cooled and highly efficient so the surface temperature of the light is very low. The normal operating surface temperature of the MIGRO LED grow light is as low as 40 Degrees Celcius or 104 Degrees Fahrenheit and the MIGRO LED grow light is comfortable to touch and have close to plants without any safety risk.

The environment

A HPS Bulb contains mercury which must be disposed of in a controlled way as it is highly poisonous to the environment. Bulb changes every few grow cycles results in a lot of toxic waste to the environment overt he course of a growers life.

Switch to LED and your light fixture will not have to be replaced for at least 50,000 hours (8.5 years @16 hours/day) and no harmful substances to be disposed of.

Last, but not least, Laziness

Have you heard the expression ‘efficiency is intelligent laziness’? I love this phrase and it’s perfectly apt for the LED vs HPS debate because:

LEDs require no bulb change, it’s a drag to need two bulbs for each grow and having to change every few grows. MIGRO LEDs output 80% of their original output for 50,000 hours (8.5 years at 16h/day). .

With an LED system like the MIGRO 400 you get even coverage across your grow. No more handling different water requirements for the plants in the centre vs the edges of the grow. The plants will love it, especially the plants at the edges.

LED grows require less heat removal. Less stressing about temperatures getting too high and noisy fans running at full speed.


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