{"id":11605,"date":"2026-10-13T09:41:08","date_gmt":"2026-10-13T07:41:08","guid":{"rendered":"https:\/\/libolux.com\/blog\/led-vs-hps-grow-lights-compared\/"},"modified":"2026-10-13T09:41:20","modified_gmt":"2026-10-13T07:41:20","slug":"led-vs-hps-grow-lights-compared","status":"publish","type":"post","link":"https:\/\/libolux.com\/en\/blog\/led-vs-hps-grow-lights-compared\/","title":{"rendered":"LED vs HPS grow lights: the comparison in numbers"},"content":{"rendered":"
Quick answer<\/span><\/p>\n

A 600 W HPS delivers around 870 \u00b5mol\/s<\/strong>; an LED giving that same light needs about 300 W<\/strong>. The switch is not \u201ca bit better\u201d: it is half the bill<\/strong> for the same number of photons.<\/p>\n

The figure that settles the argument is efficacy<\/strong>, in \u00b5mol\/J. Good HPS tops out at 1.7; poor HPS sits at 0.94. A decent current LED is at 2.5\u20133.0. Everything else \u2014 spectrum, heat, lifespan \u2014 comes after that number.<\/p>\n<\/div>\n

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The one figure that compares the two technologies<\/h2>\n

Comparing HPS with LED by wattage means nothing: the watt measures what you pay, not what the plant receives. The figure that does compare them is photon efficacy<\/strong> in \u00b5mol\/J \u2014 the micromoles of usable light out per joule of electricity in.<\/p>\n

And here the numbers are published and measured, not estimated. In the reference measurements by Nelson and Bugbee, a 400 W HPS on a magnetic ballast gives 0.94 \u00b5mol\/J<\/strong> and a 1,000 W double-ended reaches 1.70<\/strong>, which is the real ceiling of the technology. On the LED side, the DesignLights Consortium has required 1.90 \u00b5mol\/J as a minimum<\/strong> to certify a horticultural fixture since 2021, and today\u2019s high end passes 3.0.<\/p>\n

The sum<\/span><\/p>\n

The ceiling of HPS is the floor of LED<\/strong><\/p>\n

The best HPS made (1.70 \u00b5mol\/J) does not reach the minimum horticultural certification asks of an LED (1.90). That is not a brand difference: it is a physics difference.<\/p>\n<\/div>\n

Translated: for the same light on the plant, HPS asks for between 50 % and 100 % more electricity. That is the whole story, and the rest of this article just puts it in euros.<\/p>\n

What comes off the bill<\/h2>\n

Enter the HPS you run, your hours and your real price per kWh. The calculation finds the smallest LED in the range that matches or beats that HPS, and tells you what you stop paying and how many months the fixture takes to pay for itself:<\/p>\n

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Two caveats so the figure stays honest. First: the payback above counts electricity only. It leaves out bulbs, which in HPS have to be changed every 9\u201312 months of use because they lose 20\u201330 % of their output, the ballast, and the cost of extracting the heat. Second: if your HPS is a few years old and has never had a new bulb, it is giving a lot less than the box says, so the real saving will be larger than the calculated one.<\/p>\n

Heat: half the problem nobody adds up<\/h2>\n

A 600 W HPS turns almost everything it does not turn into light into heat. In a closed tent that means a bigger extractor, more noise, more extractor consumption and, in summer, the usual fight to keep the room below 28 \u00b0C.<\/p>\n

A 300 W LED giving the same light generates roughly half the heat, and spreads it over a large surface instead of concentrating it in one point. That changes three practical things: you can lower the fixture without burning, the extractor works less and in summer the room is governable.<\/p>\n

There is an honest point against it: in winter and in cold rooms, HPS heat was free heating. Switching to LED, there are garage and uninsulated-warehouse grows where the temperature drops further than it should and has to be made up. That is not a reason to keep HPS, but it is worth planning for.<\/p>\n

Spectrum: where HPS really loses<\/h2>\n

High pressure sodium emits almost everything in the yellow-orange, with very little blue and little deep red. It works \u2014 people grew with it for forty years \u2014 but it forces you to run one single light recipe for the whole cycle.<\/p>\n

A full-spectrum LED with high-efficacy white diodes covers the photosynthetic range continuously and allows two things HPS does not: seeing the plant\u2019s real colour (a nitrogen deficiency under HPS is caught late, because everything looks yellow) and adjusting intensity without changing the spectrum.<\/p>\n

What you should not buy is the \u201cmagic spectrum\u201d story. Purple panels of pure blue and red diodes were an attempt to save watts back when whites were expensive; today a good white gives more usable photons per joule and lets you see the crop. If a spec sheet boasts about spectrum but does not publish \u00b5mol\/J, it is selling the colour, not the light.<\/p>\n

Lifespan and what each one costs to keep running<\/h2>\n