Can you leave grow lights on 24 hours a day? [A Quick Guide]

LED Grow Lights in greenhouse 

Grow lights are an essential tool for growing plants indoors. They provide the necessary light that plants need for photosynthesis, as well as having several other benefits - the main one being that you can have light shining on your plants for longer than the natural daylight hours where you live. 

However, many growers wonder if it is safe to leave grow lights on for 24 hours a day. Is it safe? Is it expensive? Will it burn the plants?

Let’s take a look.

Can you leave grow lights on 24 hours a day?

The short answer is yes, indoor grow lights can be left on for 24 hours a day. However, there are some important factors to consider before doing so.


The type of plants you’re growing

The first and most important factor is the type of plant you are growing. Some plants, such as succulents, cacti, and other desert-dwelling plants, can handle 24 hours of light without any issues. They have adapted to be very resilient plants, and will be more than able to handle daylight 24/7.

However, other plants, such as tomatoes, cucumbers, and peppers, require a period of darkness to properly grow and produce fruit.

For these types of plants, you should be looking at 8-10 hours of light, similar to normal daylight hours they would receive if they were growing outdoors under natural sunlight.


How intense your grow lights are

Another important factor to consider is the intensity of the light.

High-intensity grow lights, such as metal halide or high-pressure sodium lights, can produce a lot of heat and can quickly dry out the soil and/or burn the leaves of the plant.

If you’re planning on leaving these types of grow lights on for 24 hours a day, your plant growth is likely going to suffer.

Lower intensity grow lights however don’t product as much heat, so leaving these types of grow lights on for 24 hours day won’t cause dry soil or burning.

So as long as you’re using a grow light that is appropriate for the length of time you want to leave it on, you will be fine. If you’re still a bit wary, a good tip would be to ensure that you have a good ventilation system installed, which will help to dissipate the heat.

This can be very effective if you live in a colder climate, as the cold, fresh air can be introduced to cool down your growing space.


How are your plants currently doing?

Finally, it is important to consider the overall health of your plants.

If your plants are already stressed or struggling, leaving your grow lights on for 24 hours a day is not going to help the situation. They need time in the dark, and more sunlight hours doesn’t mean more growth.

As always though, it is best to consult with a professional or do further research on the specific needs of your plants you are growing before making a final decision on this. Because it might be the case that your plants aren’t currently getting enough light, but 24 hours of light might be too much, whereas 12-16 would be ideal.


Is leaving grow lights on 24 hours a day safe?

There are many different types of grow lights, from LED to incandescent to fluorescent lights. However, as LED grow lights are the most popular, we will talk specifically about LED grow lights here.

Yes, LED grow lights are incredibly safe, and you won’t have any safety issues leaving them on for 24 hours a day.

This is because LED grow lights produce less heat than other types of grow lights, and in addition they have a lower energy consumption as well as a longer lifespan.

Now it should be said however that you need to use your grow lights in accordance with the manufacturer’s instructions - but as a general rule LED grow lights can be left on 24/7.


Closing Thoughts

In conclusion, leaving indoor grow lights on for 24 hours a day can be beneficial for some plants, but it is important to consider the type of plant, the intensity of the light, and the overall health of the plant before doing so.

If you’re worried about whether your grow lights will cost you a lot in electricity, don’t be - we have a full article on this here (the short answer is no, it won’t!).