Quick Answer: Switching from HPS to LED Grow Lights
- Modern LEDs deliver equal or better yields than 600W HPS at significantly lower electricity cost and with less heat.
- HPS heat naturally maintained VPD and temperature during veg, which LEDs do not replicate without active equipment.
- LEDs increase magnesium demand due to higher photosynthetic activity. Most growers need to add a Cal-Mag supplement after switching.
- LEDs excel most clearly in late flowering, where lower radiant heat improves terpene preservation and Brix levels.
- Switching usually requires adding a grow room heater, humidifier, and dehumidifier to replace the environmental work HPS used to do passively.
- Both light types can be optimised with proper climate control. The transition typically takes one full cycle to adjust to.
Switching from HPS to LED Grow Lights: Complete Guide
Switching from HPS to LED grow lights is worth it for most Australian indoor growers. Modern LEDs like the SANlight EVO deliver equal or better yields than 600W HPS at significantly lower electricity cost, with less heat to manage. The transition takes one cycle to adjust to, and most growers don't go back. This guide covers the real differences between the two technologies and how to optimise your setup after switching.
What HPS grow lights are and why they worked so well
HPS (High Pressure Sodium) lights are a type of high-intensity discharge lighting that produce strong output in the red and orange spectrum. They dominated indoor growing for decades and for good reason. In enclosed spaces like grow tents, the heat HPS lights produce naturally increased ambient temperature, boosted humidity when enough plant biomass was present, and helped maintain a favourable VPD. Many growers were hitting near-optimal conditions during vegetative growth without needing additional equipment. The light did the environmental work for them.
Where HPS falls short
HPS systems consume significantly more power than modern LEDs, making them expensive to run long term. During flowering, the heat they produce becomes a liability rather than an asset. High canopy temperatures reduce Brix levels and terpene production, directly affecting the aroma, flavour, and quality of the final product. HPS also lacks the spectral control that modern LEDs offer, and bulbs degrade over time and require regular replacement.
Why growers are switching to LED
Modern full spectrum LED grow lights deliver equal or greater usable light at a fraction of the power consumption. Lower electricity costs, less heat output, and a lifespan of 50,000 hours or more make them a better long-term investment. LEDs also give growers precise control over spectrum and intensity, which HPS cannot match. Where HPS created the environment for you, LEDs give you the tools to build a better one deliberately.
Where LEDs outperform HPS most clearly
LEDs excel in the late flowering stage. Because they produce less radiant heat, leaf surface temperatures stay lower, plants experience less stress, and terpene preservation improves. Brix levels can increase as a result. The final product from a well-dialled LED grow consistently shows better flavour, aroma, and overall plant expression compared to HPS at the same stage.
The magnesium demand increase under LED
A commonly overlooked factor when switching to LED is increased magnesium demand. Higher light intensity and increased photosynthetic activity under full spectrum LEDs means plants draw more magnesium than they would under HPS. Growers switching from HPS often need to adjust their feeding schedule and supplement with a Cal-Mag product, particularly in the vegetative stage. Our epsom salts and Cal-Mag guide covers why a proper Cal-Mag supplement, rather than epsom salts alone, is the better fix for this specific LED-driven demand increase.
Managing the environment after switching to LED
LEDs produce less heat, which can slow vegetative growth in cooler environments if not managed. Without the passive warmth of HPS, humidity often drops and VPD can shift out of range. To get the best results from LEDs in Australian conditions, most growers need a grow room heater for cooler months, a humidifier to maintain VPD during veg, a dehumidifier for flowering, inline exhaust fans with temperature and humidity controllers, and oscillating fans for airflow. Dialling in these factors is what unlocks the full performance advantage of LED over HPS.
Can you still optimise an HPS setup
Yes. Growers running HPS can still fine-tune their environment using dehumidifiers, humidifiers, temperature-controlled exhaust systems, and fan speed controllers. The fundamentals of environment management apply regardless of light type. HPS just requires more active cooling and humidity management during flowering than LED.
Hydroponic light systems and grow lamps in Australia
For the full range of hydroponic light systems and grow lamps available in Australia, including the SANlight EVO Series and other high-performance options, browse our lighting collection.
What to Buy for the Switch
The SANlight EVO Series is the direct replacement this guide is built around, matching or beating HPS yield at meaningfully lower running cost and heat output.
Since this guide covers the environmental gap LED leaves behind, the heat and humidity HPS was passively providing, budget for a Cal-Mag supplement from day one since LED increases magnesium demand, and a dehumidifier like the Ora 60L if your space runs more humid without HPS heat keeping it in check.
Frequently Asked Questions
Will switching from HPS to LED reduce my yields?
No, modern full spectrum LEDs deliver equal or greater usable light than HPS at a fraction of the power consumption. Most growers see equal or improved yields once the transition cycle is complete.
Do I need to change my nutrients when switching to LED?
Often yes. LEDs increase magnesium demand due to higher photosynthetic activity, so many growers add a Cal-Mag supplement after switching, particularly during vegetative growth.
Why does my grow room feel colder after switching to LED?
HPS produces significant radiant heat that LEDs do not replicate. Without that passive warmth, ambient temperature and humidity can drop, especially during cooler months, so a grow room heater is often needed to compensate.
Is HPS still worth using in Australia?
It can be, particularly in colder states during winter where HPS heat reduces or eliminates separate heating needs. HPS just requires more active cooling and humidity management during flowering than LED.
How long does it take to adjust to growing under LED after using HPS?
Most growers find the transition takes about one full grow cycle to dial in new environmental settings and feeding adjustments before results stabilise.