Grow Light Vs. Sad Light: Pros, Cons, and Key Differences

grow light vs sad light

Grow lights and sad lights may seem similar at first glance – they’re both artificial light sources used for specific purposes. But when you dig deeper, there are some notable differences between the two in terms of their lighting characteristics, intended uses, benefits, and potential downsides.

Whether you’re looking to supplement natural sunlight for your plants or trying to combat seasonal affective disorder (SAD), understanding the nuances between these two types of specialty lighting is important. Read on for an in-depth comparison and our recommendations.

Table of Contents

A Brief Comparison Table

MetricGrow LightsSad Lights
PurposePromote plant growth indoorsTreat seasonal affective disorder in humans
Light colorBlues, reds, orangesWhite or blue-enriched
IntensityHigh (20,000+ lux)10,000 lux or less
Heat outputVaries by type, HID runs hotLow heat for user safety
CustomizationTailored by spectra, intensity, timingSet output to mimic daylight
Coverage areaOver grow spaceSmall personal area
TimingAdjustable photoperiodsFixed morning use
Cost$100-$1000 for setup$30-$200 per lamp
LifespanLEDs last longestLEDs last longest
Light sourceLED, HID, CFL, fluorescentLED or fluorescent
Eye safetyModerate to high risk; use cautionTested for low eye strain
BenefitsYear-round plant growthIncreased energy and mood
UV emissionVaries, most have UV filtersNone

The key takeaways are that grow lights are designed specifically to nourish plants, while sad lights are optimized for safe use in treating human conditions. The different applications necessitate different lighting characteristics.

While there may be some overlap in light color, the divergence in intensity, coverage, heat output, and intended benefit make grow lights and sad lights distinct tools for their own purposes.

What Are Grow Lights?

Grow lights are artificial light sources used to stimulate plant growth, especially in indoor gardening situations where natural light may be insufficient. They are designed to provide the right wavelengths and intensity of light that plants need for photosynthesis.

The main types of grow lights are:

  • Fluorescent grow lights – Standard fluorescent tubes that emit light in the blue and red spectra ideal for plant growth. Affordable option good for starting seedlings and houseplants.
  • LED grow lights – LED panels or bulbs that provide full-spectrum light customized for plant growth and flowering. Energy efficient and long-lasting.
  • High-intensity discharge (HID) lights – Includes metal halide and high-pressure sodium lights that produce intense light optimal for flowering and fruiting stages. Can run hot.
  • CFL grow lights – Compact fluorescent lights that are inexpensive and easy to set up for growing smaller plants. Don’t produce as much light as HID options.

Grow lights allow gardeners to cultivate plants year-round independent of outdoor conditions. They are tailored to provide light in the spectra chlorophyll absorbs best – blues, reds, and oranges. Intensity, wavelengths, and photoperiods can be controlled for optimal growth.

What Are Sad Lights?

Sad lights, also known as light therapy lamps or boxes, are designed to treat symptoms of seasonal affective disorder (SAD). SAD is a type of depression that emerges seasonally, most often during fall and winter months.

Sad lights mimic natural daylight indoors, increasing environmental light exposure that may be reduced in winter. Daily use helps reset the body’s internal circadian rhythms and lift mood.

Sad lights should emit at least 10,000 lux of brightness, which is equal to the intensity of natural light just after sunrise or just before sunset. The light should be white or blue-enriched to properly stimulate receptors that influence mood and alertness.

Portable sad light boxes and lamps are convenient for use at home or work for 30 minutes to a few hours daily. They help combat low energy, feelings of depression, lack of concentration, and disrupted sleep patterns caused by SAD.

Key Differences Between Grow Lights and Sad Lights

While both provide supplemental artificial light, there are some key factors that distinguish grow lights from sad lights:

  • Purpose – Grow lights are designed for plant growth and development. Sad lights are designed for human health.
  • Light color – Grow lights emphasize blues and reds optimal for photosynthesis. Sad lights emit bright white or blue-enriched light like natural daylight.
  • Light intensity – Grow lights are often intense enough for flowering/fruiting plants (20,000+ lux). Sad lights provide 10,000 lux or less.
  • Heat output – HID grow lights run very hot. Sad lights stay cool for user safety and comfort.
  • Customization – Grow lights can be tailored by spectra, intensity, and photoperiods. Sad lights provide set, static outputs.
  • Coverage area – Grow lights are made to cover a grow space. Sad lights illuminate just a small area for one user.
  • Timing – Grow lights can be run on schedules ideal for plant growth stages. Sad lights are used for a set time each morning.

While some LED grow lights emit white or blue light, the intensity, coverage, and purpose make them impractical to use as sad lights. The differing needs of plants and humans necessitate lights designed specifically for each use.

Pros and Cons of Using Grow Lights


  • Allow year-round indoor gardening independent of outdoor conditions
  • Customizable to the specific light needs of any plant
  • LED and fluorescent options are energy efficient
  • Provide excellent light for seed starting, propagation, and supplementing natural sunlight
  • Help maximize plant growth, flowering, and fruiting
  • Allow rare plants or produce to be grown that wouldn’t thrive outdoors locally
  • No need for large bright windows; can transform any indoor space into a grow area


  • HID options use more electricity and run very hot
  • Higher startup costs than gardening naturally outdoors
  • Improper use can result in spindly, weak plants; requires some research

-Daily operation, adjustments, and maintenance required

-Less full-spectrum and uniform than natural sunlight

-Doesn’t provide plants all the benefits of outdoor growth like fresh air circulation

-Can promote mold growth if humidity isn’t regulated

Pros and Cons of Using Sad Lights


  • Effective, convenient treatment for seasonal affective disorder
  • Portable and easy to use daily at home or work
  • Mimics natural outdoor light exposure
  • Non-drug treatment with minimal side effects
  • Improves mood, energy, focus, sleep in SAD sufferers
  • May benefit shift workers on irregular schedules
  • Versatile for use while working, reading, eating, etc.


  • Not a cure for SAD; requires ongoing daily use
  • Effects diminish if not used consistently
  • May cause headaches or eyestrain at first
  • Relatively expensive initial investment
  • Results may take several weeks or months
  • Not clinically proven to boost vitamin D
  • Only treats SAD, not other forms of depression
  • Not a replacement for outdoor light exposure and activity

Comparing Specific Grow Light and Sad Light Products

To make the differences between grow lights and sad lights even more clear, let’s compare some popular models and their specs side-by-side:

Mars Hydro TS 600W LED Grow Light

  • Intended use: Indoor gardening
  • Light color: Blue, red, white
  • Brightness: 120,000 lux
  • Coverage area: 2′ x 2′
  • Heat output: Low
  • Special features: Dimmable, auto timer

This LED panel provides a balanced spectrum for seedling through flowering stage growth. The dimmable brightness caters to different plant types. But the intensity and wavelengths make it unsafe and ineffective as a sad light.

Circadian Optics Lumine Light Therapy Lamp

  • Intended use: Sad light therapy
  • Light color: White, 5500K
  • Brightness: 10,000 lux
  • Coverage area: Small desktop size
  • Heat output: Very low
  • Special features: Timer, compact

With light optimized for humans and clinically-tested benefits for seasonal affective disorder, this sad light is ideal for personal use. But the small coverage and low intensity would fail to support plant growth processes.

Sun Blaze T5 Fluorescent Grow Light

  • Intended use: Grow light
  • Light color: Blue, red
  • Brightness: 15,000 lux
  • Coverage area: 4′ long fixture
  • Heat output: Moderate
  • Special features: Daisy chainable

The blue and red light from this fluorescent tube promotes leafy growth but isn’t suitable for flowering fruiting plants. The T5 bulb runs hotter than LEDs. Too intense for eye health when used for long periods.

Carex Day-Light Sky Light Therapy Lamp

  • Intended use: Sad light
  • Light color: Blue-enriched white
  • Brightness: 10,000 lux
  • Coverage area: Small angle
  • Heat output: Very low
  • Special features: Portable, battery-powered option

With the same clinical specifications as other sad lamps but in a convenient travel size, this light therapy lamp is ideal for portable SAD treatment. The cool operation and limited light spread keep it safe for human use.

Philips HPS HID Grow Light System

  • Intended use: Fruiting/flowering grow light
  • Light color: Warm white
  • Brightness: 95,000 lux
  • Coverage area: Up to 15 sq. ft.
  • Heat output: Very high
  • Special features: High intensity output

This HID system delivers intense light ideal for the fruiting and flowering growth stage. But the heat and brightness risks eye damage with prolonged exposure, making it unusable as a sad light.

Verilux HappyLight Lucent Sad Light

  • Intended use: Sad light therapy
  • Light color: White, 5000K
  • Brightness: 10,000 lux
  • Coverage area: Adjustable
  • Heat output: Very low
  • Special features: Natural light color

With clinically-proven benefits for improving energy, focus, and mood in SAD sufferers, this standardized sad light is safe and effective. But it lacks the intensity and wide coverage to support robust indoor plant growth.

Determining the Best Light for Your Needs

Choosing between a grow light or a sad light comes down to matching the product specs and benefits to your specific needs and application, whether that’s enhancing your indoor garden or combating seasonal affective disorder symptoms.

If you’ll be relying on artificial light to help plants through seed starting, propagation, vegetative growth, and flowering, invest in a high quality grow light designed specifically to nourish plants. Choose between fluorescent, LED or HID systems with intensities and wavelengths tailored to your garden.

For relieving seasonal depression, only use purpose-built sad lights designed and tested to safely deliver 10,000 lux of illumination without unhealthy intensities or wavelengths. Portable white or blue-enriched lamps can conveniently deliver light therapy at home or work.

While you can’t swap a grow light for a sad light or vice versa and get the same results, understanding how the two differ will ensure you end up with the right supplemental lighting solution. Consult this guide when deciding whether you need a plant-nourishing grow light or a mood-enhancing sad light.

Frequently Asked Questions About Grow Lights and Sad Lights

Can I use a grow light for SAD?

Grow lights are not suitable as sad lights for human use. Their intense output, wavelengths tailored to plants, potential UV emissions, and heat can cause eye strain, headaches, and other issues if used as a sad light alternative. Always opt for a purpose-built sad light therapy lamp instead.

Can you get vitamin D from grow lights?

No, grow lights won’t boost vitamin D. The UVB wavelengths needed for vitamin D production in humans are filtered out for safety. Go outside midday or use a dedicated UV lamp for light-sourced vitamin D.

Can grow light replace sunlight?

While grow lights enable indoor cultivation, they can’t fully replace the spectrum and benefits of natural sunlight over the long-term. Outdoor-grown plants utilize the full spectrum of sunlight along with fresh air for robust growth. Balance indoor and outdoor growing.

Which light is better for plant growth?

Sunlight is best, but for indoor growing under artificial light, LED or HID grow lights tend to promote the most vigorous plant growth and fruiting. Fluorescents work for leafy greens and seedlings, while incandescent grow lights are ineffective.

Are grow lights safe for human eyes?

It depends on the type. LEDs are safest, fluorescents are moderate risk, but HID grow lights pose high risks to unprotected eyes and skin. Never directly stare into grow lights, especially HID lighting. Wear protective gear if working around intense grow lights.

Who should not use a SAD light?

Those with pre-existing eye conditions or who are taking photosensitizing medications should consult a doctor first, as bright light therapy could potentially aggravate these issues. It should be avoided in those with retinal damage or who are on drugs like lithium, melatonin, or St. John’s Wort.

Do grow lights emit UV?

It depends. Fluorescents don’t emit UV, LEDs emit low levels, while HID grow lights can emit significant UV if not properly filtered. UV exposure requirements vary by plant – e.g. orchids need some while other plants are sensitive. UV can also degrade fixtures with prolonged exposure.

Can grow lights cause sun damage?

Overexposure to intense grow lights can potentially cause eye and skin damage similar to natural sunlight, including dryness, pigmentation, wrinkles, and higher skin cancer risk. Always take precautions around UV-emitting HID lights. LED grow lights are safer.

What type of UV is grow light?

HID grow lights produce UVB and UVA rays like sunlight if not properly screened. However, wavelengths are slightly different than outdoor UV. UV from grow lights accelerates flowering in plants, but impacts on humans remain less studied. LED grow lights have negligible ultraviolet components.


To recap, grow lights and sad lights serve very different purposes and have unique characteristics that make each one suited for their intended application. Grow lights enable indoor gardening by delivering the particular wavelengths and intensities of light that stimulate plant growth and flowering. Sad lights treat seasonal depression in humans by mimicking the look and brightness of natural daylight.

While an LED or fluorescent grow light could technically emit white or blue-enriched light, they lack the strict testing for eye safety and clinical effectiveness that purpose-built sad light lamps undergo. The relatively high intensity of grow lights also makes them impractical for human use.

Always choose the proper tool for the job. Use grow lights to nurture your plants indoors when sunlight falls short. Turn to dedicated sad light boxes and lamps to get your daily dose of bright light for your mind and body.

Cathryn Thompson

Hi, I am Cathryn Thompson. I am a full-time blogger. I ditched my 9-5 job many years back to explore life a bit more. In this blog, I like writing about everything that can save us from the monotony of regular life and live our life to the fullest.

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