HPS vs LED Grow Lights

HPS vs LED Grow Lights

In this post, we will show you the differences between a High-Pressure Sodium light and COB-LEDs and highlight why the LED system represents a big step forward in the field of plant lights. We will begin with a look at the basic equipment. Since we want to compare the efficiency of both systems, we’ll put together two 400 watt setups.


400w High Pressure Sodium

  • Components: 400w HPS bulb (i.e. Sunmaster) 400w light ballast reflector(Adjust-A-Wing) and socket cables HPS data: lumen: ca 52.000lm luminance efficacy: up to 130lm/w thermal loss: at least 60% efficiency: 25%-40%

4Seasons - Luma 4

  • lumen: ca 72.800lm luminance efficacy: up to 182lm/w thermal loss: at least 35% efficiency: 45%-65%

Gas-discharge lamps like High-Pressure Sodium lights spread their light in all directions. As a result, 50% of the light needs to be reflected which in turn leads to a considerable loss of light. Our LED plant lights equipped with Citizen & CREE LED-chips have a dispersion angle of 115°. Combined with high quality 90° lenses that boast 92% Light Transmittance.


After comparing setups and technical performance values of High-Pressure Sodium lights and Citizen & Cree LEDs we will now cover some essentials and then show the results of our comprehensive tests.


The spectrum of visible light The key to evaluating the performance of a plant light is measuring its PPFD-value (Photosynthetically Active Photon Flux Density). Photosynthetically active radiation denotes the spectrum of sunlight which is used by photosynthetically active lifeforms for growth and flower formation. This spectrum encompasses wavelengths from about 400nm (high-energy blue light) to 700nm (low energy red light).


Lumen is for human - let’s measure PPFD PPFD-values are specified in micromole per square meter and second. The PPFD-value states how many photosynthetically active photons hit an area of 1 square meter over the course of 1 second. When evaluating a plant light it is important to measure its PPFD-value on several different spots to determine a sound average. This average PPFD-value can be used to determine how effectively a plant light will stimulate plant growth.


  • average PPFD of 618 μmol/m²s • light distribution shows clear fall-off towards the edges • light spectrum almost exclusively confined to yellow-red zone





4Seasons Luma 4



  • average PPFD of 811 μmol/m²s • even light distribution and overall higher values, especially on the edges • full white color spectrum covering all color temperatures

Visualizing the measured data clearly shows that the COB-LEDs reach significantly higher PPFD values than the High-Pressure Sodium light. While the HPS reached an average of 618 μmol/m²s, the LED plant lights surpassed this value with 811μmol/ m²s under the same conditions. While both light setups operate on the same nominal power, the higher effectiveness of the Cree and Citizen LED chips leads to an overall significantly higher efficiency factor. As a result, the LEDs can be dimmed to achieve the same output while using less energy than the HPS. Whether you need lights for plant propagation, overwintering, growing or flower phases - thanks to its high PPFD-value, LED technology is ideal for all aspects of plant lighting

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