Grow Lamp Replacement Test

grow lamp replacement test


Grow Lamp Replacement Test

What Difference Does it Make?!

Our Grow Lamp Replacement Test, SEE For Yourself…

It was time for a test grow facility to change their lamps-or according to lamp manufacturers and popular grow literature, it was actually long overdue. This provided the perfect opportunity for Grozine to conduct a simple, real world grow lamp replacement test to see how much light, if any, hydroponics growers were not getting but paying for in electricity by not replacing lamps HID grow lamps  more frequently.


digilume digilux hps grow lamps


Typically, most indoor growers using HID crop lighting systems like HPS or MH as a sole source of light for plant growth are told to replace lamps every 6 months with regular use-these lamps went almost a year and a half–THREE TIMES the recommended replacement period!



Common Reasons Given for Frequent Lamp HID Grow Replacement:

  • Ballast draws same electricity, eg 1050 watts, but produces less light because the bulb is aging after 6 months
  • “Color Shift” may occur-the lamp color characteristics for growth change 
  • You will have a higher yield after replacing lamps


Reasons Growers Don’t Like Replacing Lamps Often:

  • Expensive, a 1000 Watt horticultural HPS lamps can cost around $100
  • It’s work-sourcing, purchasing and replacing lamps
  • Lamp disposal and guilt-lamps contain heavy metals that are toxic
  • It’s almost too bright already with 1KW of lighting every 3 or 4 feet


 The Test:

Nothing fancy, we used a Milwaukee Instuments Lux/Lumens meter.  We can’t measure any changes in color with this; just intensity in one of the bandwidths.  This is perfectly fine when comparing relative apples to apples, in this case one HPS grow lamp to another.  If we were looking for very slight differences, it might matter more that the two lamps Diglux (original to be replaced) and the New Digilume HPS horticultural lamp and not 100% identical.  However, since we expect to see some difference after 18 months of use in an item that costs a hundred bucks to replace, this test will tell us what we need to know:

Does it really make a difference if you replace your HPS or MH grow lamps?

So here’s what we did to find out, again, nothing fancy here–real world stuff.  Without cleaning the air cooled reflector lens (which should be done frequently) the old lamp was removed after taking a measurement (lamp in operation several hours) with our Lux/Lumens tester and then unplugging.  The measurement was taken (as pictured below) at a measured mark under the original lamp. We then replaced with the brand new out of the box lamp and let it run for only about an hour (most “experts” will say to run for several days to stabilize-again, we are looking for simple and bigger differences, not small stuff))


*Old* HPS Grow Lamp: 10, 900 lumens one foot from the air-cooled glass tube surrounding the lamp

*New* HPS Grow Lamp: 13,700 lumens one foot from the air-cooled glass tube surrounding the lamp



hps grow lamp digilux after one year
HPS Grow Lamp-18 months OLD, 10,900 lumens
hps grow lamp digilume new
HPS Grow Lamp-Brand NEW, 13,700 lumens


Pretty big difference in lamp intensity was measured.  As a percentage, that’s about 25% less light from a 1000 watt HPS grow lamp after around 18 months of regular use

Does this mean you should replace your lamps every 6 months?

Not necessarily, here are some final thoughts on what you should weigh-in on when considering what your threshold is for determining when to replace your grow lamps:

  • cost of electricity-you are paying for, but receiving around 25% less light after 18 months
  • cost of lamp replacement-purchase, shipment, labor and safe disposal
  • what level of light do your plants need-is it overkill or are you under illuminating? SEE DLI for a better understanding
  • environmental impact-the metals like mercury and lead in the lamps you throw away


About Erik Biksa 247 Articles
Erik Biksa has been writing about and discussing hydroponics growing, related technologies and cropping methods since 1999 in a variety of professional publications and platforms globally Erik has travelled the world learning and teaching modern growing techniques and technologies and is appreciated by many growers for his informative yet hands on approaches. Presently, he is the Editor at Grozine Hydroponics Mag.