How many LED growing lights do you need and how long should they lighting every day ?

The most important device in your planting room is the light, why? Light is the food of your plant, you need to feed your plants with high quality food to produce high quality yields. Due to its energy efficiency, durability and full spectrum, LED plant growing lights are now considered by most growers to be the best lighting choice. However, finding the right LED plant light for your plants is not an easy thing with only the options and technical parameters provided by the seller or manufacturer.
Today, we will answer two questions that we are often being asked about.

The first question: What size LED growing light do I need?

To calculate the required LED growing lamp size, you first need to calculate the exact size of the growth space.
A good experience when growing plants with LED growth light is to use at least 40 watts of light per square foot of growth space. We want to flood our plants with light so that they have a lot of energy to germinate, grow, and bloom. Therefore, we need to calculate the total square feet (length x width) of the growth space. Then we multiply this number by 40 watts to give us the approximate wattage of the light we need.
For Example: I have a 4 foot long, 3 foot wide growth space. This gave me a 12 square foot (4 feet x 3 feet) growth space. Then I multiplied this number by 40 watts, which gave me 480 watts. So, in this example, I need (an) LED growth light(s) of at least 480 watts.

How many plants can I grow?

Most LED growth lamps are typically capable of covering about 1-6 plants, in a number such that the plant does not hinder the growth of other plants, and you can also search the internet for the specific plant spacing required for plant growth. If you want to plant a larger number of plants, buy multiple LED plant growing lights, installed them side by side or a high power LED plant light to ensure that each plant gets enough light.
Important Note: 1 square foot of growth space = minimum 40 watts of LED growth light
Please note that,lighting intensity needed for different planting period is totally different. Below is a typical lighting intensity ( it is being called by PAR,it is part of the spectrum that plants use for photosynthesis, measured by μmol/m2/s; the higher the PAR output of light is, the more light the plant receives.) needed for general plant growing in different period.

Different Period Of PlantReference PAR Output Needed
Seedling200-400 (μmol/m2/s)
Veg400-600 (μmol/m2/s)
Flowering600-900 (μmol/m2/s)

Keep in mind that these are the best levels of PAR. Using a PAR output below these ranges of growth lights will not be a disaster and you will not maximize the potential of the plant. In this case, the customer should manually adjust the illumination height of the LED plant growth lamp (the lower the height of the plant lamp is, the larger the PAR output will be), so that the plant can grow better. For business users, we recommend you to buy high-power LED plant lights.

Second question: How many hours should the plant growing lights be illuminated each day?

LED plant growth lamp for indoor gardening

Seedlings and high light needed plants
For optimal growth, seedlings and high light needed plants were placed approximately 6 inches below the LED plant light which containing the full spectrum light, which required approximately 16 to 18 hours of artificial light per day. By placing reflectors around the LEDs to ensure they achieve uniform illumination and maximum light intensity, this will reflect all light to the top and sides of the plant. You can also light up 24 hours every day if you like.
Low light and medium light need plants
Most common indoor plants can grow well under artificial light for 12 to 14 hours without any sun exposure. Medium light needed plants require approximately 6 hours of sunshine per day, so they can benefit from higher light intensities and work best when they are no more than 1 foot away from LED plant lights. Low light needed plants usually grow well in shade or in direct sunlight of less than four hours, so you can set them 2 to 3 feet away from the fixture. Although these plants have different light requirements, at least 6 hours of artificial lighting should be guaranteed when provided by artificial lighting. If your plants receive some daylight, but do not meet their needs, such as from nearby windows, then you should provide them with an additional 2 to 6 hours of artificial light at night.

LED plant growth lamp for outdoor gardening

The function of LED growing lamp is to supplement light. Firstly it can strengthen the light intensity of the blue and red areas in the case of sunshine during the day, and promote the photosynthesis of plants, secondly to compensate and promote the plants when there is no sunshine at night and speed up the growth process;

The lighting time of the LED plant lights needs to be considered which growth stage the plant is in, such as the nursery period or the flowering period. This can greatly reduce the unnecessary consumption of energy, and at the same time effectively increase the yield of fruits and vegetables.