Best Grow Lights for Cannabis | LED vs HPS Explained

• May 19 2025, by Noah
• 5 min reading time

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Want to grow weed indoors? Then good lighting is crucial for healthy growth and maximum yield. In this blog, you'll discover the best grow lamp for cannabis, what wattage you need, and which lamp suits your setup.

Want to grow weed indoors? Then good lighting is crucial for healthy growth and maximum yield. In this blog, you'll discover the best grow lamp for cannabis, what wattage you need, and which lamp suits your setup.

Why good lighting is essential for cannabis plants

Lighting is the heart of any indoor grow. Without sufficient light, a cannabis plant cannot perform photosynthesis – the process where light is converted into energy for growth, leaf development, and eventually buds. Outdoors, the sun provides this light, but indoors it's up to you to provide the correct spectrum and daily light quantity.

What exactly does light do for a cannabis plant?

A cannabis plant uses light to:

• Store energy for cell growth
• Develop new shoots and leaves
• Produce resin-rich buds during flowering
• Stimulate internal processes like root development, water absorption, and nutrient uptake

The better and more stable the light, the healthier the plant – and the higher your yield.

The right light schedule for your cannabis plant

One of the most important aspects of lighting is the light schedule – the hours of light and dark you give the plant. This schedule determines the growth stage:

Vegetative phase

• Light schedule: 18 hours light / 6 hours dark (18/6)
• Goal: Maximum leaf development, root growth, and stretching
• Light spectrum: Rich in blue light (cool white/blue)

Tip: Some growers use 20/4 or 24/0 for faster growth, but rest is also important.

Flowering phase

• Light schedule: 12 hours light / 12 hours dark (12/12)
• Goal: Bud and flower production
• Light spectrum: Rich in red light (warm white/red)

By switching from 18/6 to 12/12, you signal the plant that "autumn" has started, triggering the flowering phase and focusing energy on bud development.

Why consistent lighting matters

Stable light cycles result in:

• Less plant stress
• Lower risk of hermaphroditism (male flowers)
• Better nutrient uptake
• Smoother growth curves

A digital timer is a must. It ensures you never forget to switch lights on or off and keeps your light schedule precise.

An energy-efficient LED lamp illuminating a growing hemp plant in the dark of a room.

Which lamp for growing weed? The most popular options

LED grow light (recommended)

LED lights are the best choice for most growers, especially beginners.

Advantages:

• Energy-efficient
• Low heat output
• Long lifespan
• Full spectrum (for both growth and flowering)

LEDs come in various wattages and sizes – perfect for any grow tent.

HPS lamp

High Pressure Sodium (HPS) lamps provide powerful, warm light and are popular for the flowering phase. They use more power and get hot, so good ventilation is key.

Advanced tip: Combine HPS with LED for optimal light spread and spectrum.

HPS lamp with orange light.

What does a good grow lamp cost?

The price of a grow lamp depends on the type, wattage, and quality. Beginners can start with a decent LED grow light from around €100. These basic models are often sufficient for small spaces or 1-2 plants.

For larger setups or lamps with advanced features (like full spectrum, built-in cooling or adjustable modes), prices can rise to €300 or more. HPS lamps are usually cheaper upfront but consume more electricity and need extra ventilation, which increases overall costs.

Wattage per m²

How many watts do you need to grow cannabis? It depends on your grow space and the number of plants.

Rules of thumb:

• 1 plant ➔ 50–100 watts
• 1 m² ➔ 300–600 watts
• Large harvest ➔ ±600 watts per m²

Note: cheaper often means less light output. Always choose a reliable, high-yield LED grow lamp.

Distance from lamp to plant

With LEDs, distance is crucial to avoid burning or stunted growth:

LED Wattage	Ideal distance to plant
100W	25–30 cm
300W	37–45 cm
600W	60–80 cm

Each lamp is different, so always check the manufacturer's specifications.

Light color and spectrum: PAR is key

Plants don’t care how bright the light looks to us – they care about usable light. This is measured in PAR (Photosynthetically Active Radiation).

• Blue light ➔ encourages leafy growth
• Red light ➔ promotes flowering
• Full spectrum ➔ ideal for all growth phases

LEDs with full spectrum are a safe and effective choice.

Useful grow light accessories

Complete your grow setup with:

• Timer ➔ for automatic light cycles
• Reflectors ➔ for even light distribution
• PAR meter ➔ to measure usable light (more accurate than lux/lumen)

This creates a stable environment for your cannabis plant to thrive.

Conclusion: what really is the best grow lamp?

For most growers, a full spectrum LED grow light is the best choice. Combine it with the right wattage, proper distance, and a phase-based light schedule, and you're set for success.

Want extra power during flowering? Combine LED with HPS – just ensure proper ventilation.

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