Should I Use HPS or LED for Growing Licensed Cannabis?

Should I use HPS or LED for growing Cannabis?

“What lighting source should I use for my licensed cannabis grow?”; “I am comparing LED to HPS for my cannabis operation. Which grow light do you recommend?” These are questions people ask the team at P.L. Light Systems almost daily. Like many aspects of growing, deciding if you should grow under HPS (high pressure sodium) or LED does not have a silver bullet answer! There are a lot of variables that need to be considered and then prioritized to your own individual operational needs and it is an important step in understanding which type of lighting will fit this critical investment.

To figure out what type of horticultural lighting you should use, begin by rating the following six factors: Budget, Maintenance, Electrical costs, HVAC requirements, Growing requirements and Spectrum, in order of your priorities.  We will overview all these factors and then review a Pros & Cons chart comparing double-ended (DE) HPS, LED and a hybrid HPS-LED system at the end to see which lighting type meets your needs.

Let’s first go over the six factors, beginning with budget.

1.Budget

The amount you have to invest, as well as your return on investment, should be key things to consider when buying a new lighting system.

Capex

• An all-LED system can be approximately 3 to 4 times the cost of an all-HPS DE system.
• LED fixtures may be eligible for local hydro incentives, which commonly require a DesignLights Consortium (DLC) Horticultural listing to qualify. These programs are run by individual utilities, hundreds of them across North America, and their terms change regularly, so check what your own utility currently offers

If you want to learn more on local rebate programs in the USA and Canada, then download our “Energy Rebate and Incentive Guide”

Opex

Warranty

• DE HPS fixtures – Have a 3-year warranty. HPS lamps have a 4-year warranty or up to 10,000 burning hours
• LED fixtures – Have a 5-year warranty, or up to 50,000 hour lifetime (a requirement to be eligible for DLC listing)

2. Maintenance

Both HPS and LED luminaires need to be cleaned and maintained to keep them working efficiently and at their highest output.  HPS luminaires require more maintenance than LEDs, since they also require re-lamping as well as reflector cleaning.

DE HPS 

• Re-lamping costs and associated labour, approximately every 1-4 years depending on your burning hours and ROI (return on investment)
• Reflector cleaning and associated labour, approximately every 1-2 years depending on your environment and resources

LED

• Lens cleaning and associated labour, approximately every 1-2 years depending on your environment and resources

To see what’s involved with cleaning and maintaining HPS luminaires watch our video on Reflector and Fixture Cleaning as well our video on How to Install a DE lamp.

3. Electrical Supply & Operating Costs

What is your current supply capacity? Do you have a limited supply that you will need to work within? Will you need to factor in the cost of adding a transformer to expand your supply?  These are all things you should consider when deciding what type of lighting you should use for your crop.

First you should figure out what the cost per kW is.  You can easily do the math:

# lighting hours annually x actual wattage of the fixtures x # of fixtures) /1000 x $/kW. 

Below we have two examples showing the difference between HPS and LED:

Example 1. DE HPS – (4000 hours x 1045W x 100 Fixtures)/1000 x $0.12 = $50,160.00 annual electrical operating cost for 100 x 1000W DE HPS

Example 2. LED (4000 hours x 640W x 100 Fixtures) /1000 x $0.12 = $30,720.00 annual electrical operating cost for 100 x 640W LED

This means a potential 38.8% kW savings

Measuring fixture efficacy is important to determine the efficiency of the light source at converting watts into photons (PPE). The higher the PPE, the better the luminaire is. It is measured in micromoles per Joule (µmol/J) and is calculated by dividing the µmol/s¹ by the wattage.

Let’s look at two examples:

Example 1. DE HPS 2150µmol/s1 divided by 1045W = 2.06µmol/J

Example 2. LED 2200µmol/s divided by 672W = 3.3µmol/J

As we can see, the LED luminaire has higher efficiency and is therefore better at converting photons into PAR energy.

Check out our Light Energy Calculator to find out more to compare efficiencies across different lighting technologies.

4. HVAC Requirements

HVAC requirements will vary based on many factors and should be assessed to determine what lighting will fit into your application.

Below we outline some things to consider when figuring out your HVAC needs.

• Geographic location: year-round temperatures can influence your HVAC needs.
• Indoor vs. Greenhouse applications will have varying HVAC requirements.

Indoor facility: The cost to cool your grow can be one of your highest production costs, and your AC load is based on the amount of BTUs produced from your luminaires. This is simple math as 1 watt equals 3.412 BTUs. No matter what 1000W HPS fixture you use the BTUs from that fixture will be 3412.

Calculate the BTU/h to size your AC = # fixtures x actual wattage x 3.41:

Example 1. DE HPS 100 Fixtures x 1045W x 3.41 = 356,345 BTU/h

Example 2. LED 100 Fixtures x 640W x 3.41 = 218,240 BTU/h = Potential 38.8% BTU/h savings

Example 3. Hybrid 1:1 50 x 1045W DE HPS+50 x 640W LED x 3.41 = 287,292.5 BTU/h

Greenhouse facility: DE HPS can reduce additional greenhouse heating by 40% in colder winter climates vs. LED.

5. Growing Practices

Growing vertically, or in a traditional single tiered facility, can help you determine if you should use HID or LED luminaires.  Let’s look at the differences between them both.

Vertical racking – Maximize your vertical footprint by minimizing the distance between shelves with fixtures closer to the crop.

• Vertical racking can increase your canopy by 100% per additional tier in the same linear footprint, with yield increasing slightly less by approx. 80% per tier due to smaller plants/less yield—but then possibly more frequent turns.
• LEDs are best suited to close-to-canopy mounting due to their lowered heat load.
• Detailed ROI is needed to include HVAC adjustments to manage vertical microclimates on each tier.

Single layer – Mounting height restrictions and available distance from the canopy should be considered. HPS luminaires require at least 3 feet from the canopy.

6. Spectrum

LED

• Tolerance & resources for the learning curve of how plants react under different spectrums to reach optimum levels
• Rebalancing inputs: temperature, CO2, irrigation, fertigation and possibly humidity.
• Opportunity to affect morphology & metabolic processes. 

DE HPS

• Tried & trusted spectrum for experienced grower, confidence in growth & yield results.
• No spectral variety or opportunity to further affect morphology or metabolic processes.

PROS AND CONS:

In the following charts, we overview the pros and cons of each type of lighting—including a hybrid LED-HPS system, to help determine what type of lighting system will work best for your application.

*Example calculations & savings are based on 640W LED & 1045W DE HPS, hybrid solution is based on 1:1 DE HPS + LED, associated costs based on $300 DE HPS fixture & $900 LED

Bottom Line:

With all these factors above, how do we answer our initial question? Quite frankly, there is no simple answer. Every grows is different – from different strains being grown, varying growing climates by geography, multiple styles of growers, indoor versus greenhouse, etc. All these factors will weigh heavily on what is better for you.

Remember to analyze and prioritize your key deciding factors and to do your homework on the best product to meet your needs and budget. Lighting is a long-term investment, so partner with a quality manufacturer that will understand your needs, and provide a detailed and professional light plan as well as after-sales support.

For more information on growing cannabis download our Cannabis Cultivation Guide, which gives advice on growing under both Led and HID luminaires.