What size of led grow light do i need? The mars hydro led grow light tent kit in the home

How to Pick the Right Size LED Grow Light?

Growing plants indoors is a great way to bring greenery into your space and enjoy fresh herbs and vegetables. However, indoor plants have different lighting needs than outdoor ones, so choosing the right LED grow light size is crucial for their growth and health. With so many options available, it can be tough to know where to start.

In this guide, we'll walk you through everything you need to know to select the perfect LED grow light size for your indoor garden. Keep reading to learn more!


Narrowing Down Your Options in 3 Steps

With an abundance of grow light options on the market, choosing the perfect one for your indoor garden can feel like a daunting task. But don’t worry—streamlining your options can make the decision process much easier. Here’s a simple, three-step guide to help you select the ideal LED grow light for your plants:

Plant Species and Their Lighting Requirements

When selecting the right LED grow light size, it's important to consider the plant species and its specific lighting needs. Different plants require different amounts of light for optimal growth. For example, plants native to sunny climates need more intense light, while leafy greens and herbs require less.

DLI, or Daily Light Integral, measures the total amount of light a plant receives in a day, usually expressed in mol/m²/day. It helps ensure plants receive the right amount of light, preventing both underexposure and overexposure. Below, we’ve listed the DLI requirements for common plants:

DLI for 15 common plants

LED grow light vendors typically provide PPFD (Photosynthetic Photon Flux Density) metrics in their specifications to demonstrate fixture performance. Once you've determined the plant's DLI and the number of hours it needs light each day, based on its species, you can do some simple calculations to determine the required PPFD.

Here's the formula, where the content in brackets is what you need to fill in:

  • [DLI] x 1,000,000 ÷ 3600 ÷ [Everyday Lighting Hours] = [PPFD]

E.G.: [50 mol/m²/day] x 1,000,000 ÷ 3600 s ÷ [18 h] = 771.6 μmol/m²/s

Therefore, if your plants require a DLI of 50 mol/m² per day, and your lighting schedule for it is 18 hours, then you need a light fixture that produces at least 771.6 μmol/m²/s PPFD.

Growth Stage

The PPFD mentioned above offers a general range for required lighting, but a plant's lighting needs can vary depending on its growth stage. Improper lighting can impact growth, flowering, and fruiting. For optimal plant health, it's important to specify the correct PPFD for each growth stage.

Mars Hydro has published a complete guide outlining the ideal PPFD for common plants at different stages of growth. For brevity, we’ll provide a quick overview here rather than a detailed explanation.

PPFD for varting plants at each growth stage

Growing Area Size and Shape

When selecting the right LED grow light size, it's important to consider the size and shape of the growing area. The size of the growing area will determine the number of LED lights required. A larger grow area will require more LED lights to ensure adequate light penetration and uniformity. The shape of the space also affects how light is distributed, as some LED lights offer a more focused beam, while others provide a wider spread of light.

If you're using a grow tent, the grow tent size becomes the most important factor. Ideally, the LED grow light coverage should match the tent size exactly. However, for plants that require less light, it's recommended to use a grow light that covers at least 75% of the tent's surface area. This ensures optimal growth for your plants while being more cost-effective.

Additionally, the height of the plants in the growing area should be taken into account, as taller plants may require more intense light and a higher wattage LED grow light to ensure proper growth and development.

What Size LED Grow Light Do I Need

After completing the three steps above, you've gathered the essential information about your LED light fixture: the required PPFD, the coverage shape, and the size of the area it should cover. Next, let's look at how to use wattage to determine the appropriate size for your LED grow light.

How Many Watts Per Square Foot for LED Grow Lights

Using wattage to determine the size of your LED grow lights was considered a common method, and you may have come across this in other articles. Let’s quickly review the general guidelines. Typically, 25-50 watts per square foot is sufficient for most plants during the vegetative stage, while flowering plants may need 40-60 watts per square foot for optimal growth.

Mars Hydro fc-3000

However, certain high-light plants, like tomatoes and peppers, may require even more wattage. It’s important to keep in mind that the efficiency and quality of the LED grow light can influence the recommended wattage per square foot. High-quality LEDs often need less wattage to produce the same light output as lower-quality options. The hanging height of the LED light from the plants also plays a key role in light intensity and can impact the wattage needed.

Ultimately, determining the ideal wattage per square foot depends on the specific needs of your plants, as well as the efficiency and quality of your LED grow light.

HPS to LED Equivalency

HPS (High-Pressure Sodium) grow lights have long been a popular choice for indoor plant cultivation. However, with the advancements in LED technology, more and more growers are making the switch to LED grow lights.

Generally, a high-quality LED grow light can produce the same light output as an HPS light while using 30-50% less wattage. For example, if you're currently using a 1000-watt HPS light, you may only need a 500-700 watt LED light to achieve the same level of light intensity.

Other Considerations

While you've learned various ways to pick the right size LED grow light, other considerations can impact the overall success of your indoor garden due to the LED grow light you choose.

Analyze PAR Maps and Light Uniformity

A PAR map (or PPFD chart) visually displays the intensity and distribution of PAR within the light coverage, typically provided by vendors. Light uniformity refers to how evenly light is distributed across a space, which can be easily assessed through a PAR map. Uneven light distribution can cause certain areas to receive too much light, while others may get too little, leading to inconsistent plant growth and yields. By measuring and analyzing light uniformity, growers can identify areas that receive more or less light and adjust their lighting systems accordingly.

PAR map or PPFD chart for selecting led grow lights

Here are some tips for interpreting a PAR map to gain insight into light uniformity:

  • Look for hot spots: Hot spots are areas where light intensity is higher than others, which can indicate poor light uniformity. Plants in these areas may receive excessive light, causing them to grow more vigorously under the hot spot, or suffer from leaf burn.

  • Look for cool spots: Cool spots are areas where light intensity is lower than others, signaling that light is unevenly distributed. These spots can affect the growth of side branches and foliage, as plants may not get enough light. In non-reflective areas or without a grow tent, cool spots can hinder plant growth and development.

  • Look for patterns: Patterns on a PAR map, especially when using multiple LED grow lights, can help identify causes of uneven light distribution. For instance, if the map shows stripes, it may suggest that light fixtures are spaced too far apart. Recognizing these patterns allows you to adjust your lighting system to achieve more even light coverage.

Dimming and Dasiy Chain Controls

LED grow lights are essential for creating the ideal environment for plants to thrive, but different plants have unique light needs at each stage of growth—seedling, vegetative, and flowering. That’s where dimming controls come into play. With the ability to adjust light intensity, you can easily customize your lighting to suit each plant's specific requirements.

But it doesn’t stop there—daisy chain controls allow you to seamlessly connect multiple grow lights, simplifying the setup and eliminating the hassle of adjusting each light individually. With just one control, you can effortlessly manage the intensity of all connected lights at once.

Dimming feature and daisy chain feature on led grow lights

For the best results, choose grow lights equipped with both dimming and daisy chain controls. This dynamic combination boosts your garden's efficiency, supports robust plant growth, and makes both setup and ongoing maintenance a breeze.

Additional Features and Customization Options

As indoor gardening continues to gain popularity, the demand for smart, customizable LED grow lights is soaring. Cutting-edge features like remote control access and scheduling allow growers to effortlessly manage their lights from anywhere, ensuring optimal lighting schedules for vibrant plant growth. Moreover, with customizable options like spectrum control and adjustable brightness, growers can fine-tune the light output to perfectly match the specific needs of their plants, creating a truly tailored growing environment.

Smart features on led grow lights

These innovative features not only streamline garden management but also elevate the growing experience, promoting healthier plants and reducing energy consumption for a more efficient and sustainable gardening journey.

Recap of Key Points

Key factors to consider include the types of plants you're growing and their required PPFD, the growth cycle the light needs to support, the size and shape of your growing area, and the ideal wattage for your plants. Additionally, features like dimming options and smart controls are worth considering.

Mars Hydro invites indoor gardeners from around the world to explore our diverse LED Grow Light Collection. With a range of options available, you're sure to find the ideal solution for your gardening needs.