LED vs HPS is a very common question for new growers. HPS lights have been the standard growing light for decades. In 2020 LED lighting is the better choice in almost all cannabis growing applications. We’ve reached a break-even point where it no longer makes sense to invest in HPS technology despite the slightly lower startup costs. See the History of LED lights for a brief background on how LED’s have evolved over the years. Even governments have gotten wise to this and are replacing HPS street lights with new LEDs.

Electricity Consumption (Efficiency)

High-Pressure Sodium (HPS) lights are inefficient when compared to LED. Up to 70% of the power is wasted as heat, you then need to expend more energy to remove this heat from your grow area. There is a direct equivalency between watts and heat, no matter which lighting source you use.
1 W = 3.412 Btu/h
So a 240W LED Board will generate the same amount of heat as a theoretical 240W HPS. The difference is that the printed LED board will yield ~2-3x more. Typically, you would need to run a 600W HPS in the same space to approach the same yield. This often leads to overheating issues. Especially with DWC where maintaining cool water temperatures (max 68F) is essential to preventing root rot.

Yield

As mentioned above-LED lighting yields on average 2x more at a given wattage. With HPS lighting hitting 1g/watt was considered a milestone.
HPS Yield:
0.25-0.5 g/watt -Average
1.0 g/watt – Expert
LED Yield:
1.0 -1.6 g/watt – Average
2.0+g/watt – Expert

Note that the ‘expert’ values above typically involve the use of co2 supplementation and providing ideal growing conditions for your plants.

Cost of Startup

Electricity savings in the first grow will cover the negligible higher initial startup cost (approx $30). You can use my electricity calculator to determine your annual electricity costs to compare. I will compare a 600W HPS with a 240w Printed LED Board as they should yield approximately the same amount.

600w HPS cost = $130 USD on Amazon (free shipping)

240w Printed LED Board = 100 + 40 Shipping + 30 Duties
240w Printed LED Board = $170 USD (via Alibaba)

As you can see the price difference for equivalent producing HPS and LED lights is only about $30 USD. In Ontario, Canada the cost of electricity (off-peak) is $0.107/kWh.

You save 340 kWh by using an LED Board over an HPS light in the example above. At $0.107 kWh it would take only 2 months of running the lights to reach your break-even point where LED is more economically viable. Over a 1-year period, you would save $164 by running an LED Board over an HPS light at the 240W LED/600W HPS level.

Humidity

Low humidity is another issue that my friends growing with HPS lights face. The bulbs act like heat lamps that dry out your leaves and ambient air. You are also having to recirculate the air in the grow-room more frequently which drops the humidity further (assuming you live in a dry climate). My buddies still growing with HPS lights tend to have to run humidifiers in their grow boxes. Since LED Boards run cool they have minimal impact on room humidity.

Fire Risk

HPS lights pose a significant fire risk when compared to LED Boards. This is because they run much hotter and have glass bulbs that can break if knocked over. If your exhaust fan fails with an HPS setup you’ll be running 2x as hot as you would with an equivalent LED Board.

To mitigate fire risk I always recommend home growers install a nest smart fire alarm. This will give you peace of mind when leaving your grow unattended. Traditional fire alarms in houses are woefully behind the times and rely on your neighbors hearing the alarm/seeing smoke and calling the fire dept.

Greenhouse Applications

The only application where I would still recommend HPS lighting is extended daylight in greenhouse grows where the extra heat they produce is beneficial. That is outside of the scope of this website which typically focuses on 4-6 plant microgrowing.