Should You Turn Your Grow Lights Off at Night?
You might be wondering if you can “hack” the system with LED grow lights.
Theoretically, leaving indoor grow lights on 24/7 should make hydroponic plants grow much faster, right?
Wrong.
Just like humans need sleep, plants require a daily period of rest in darkness. You can do more harm than good if you do not turn grow lights off at night.
Here’s why.
Why Hydroponic Plants Need Darkness
Like animals, plants have a biological clock that regulates their growth and development.
Darkness is a key signal in this circadian rhythm. It helps indoor plants distinguish between day and night.
When plants are under LED grow lights during the day, they primarily use photosynthesis to convert light into energy.
At night, they rely on respiration, converting glucose and oxygen into energy.
Like photosynthesis, respiration is essential for healthy hydroponic plant growth and development.
Many plants also require periods of darkness for flowering and fruiting.
How Many Hours of Grow Light Do Plants Need Each Day?
Most plants need roughly the same amount of rest each day as humans, away from bright indoor grow lights.
Exact light exposure recommendations vary depending on the plant type and growth stage. As a general guide:
- Mature plants should spend 12 to 16 hours under grow lights each day
- Seedlings can usually receive 14 to 18 hours of grow light per day
- Grow lights should usually be turned off for 6 to 12 hours each night
Because these ranges are general, always research the specific light cycle needs of the hydroponic plants you are growing.
How to Know if Plants Need More Darkness
Plants usually show visible signs of stress if they receive too much grow light and not enough darkness each night.
Signs to look out for include:
- Leaf burn
- Yellowing leaves
- Pale leaves
- Stunted growth
- Wilting
If you notice these signs, you may need to turn your grow lights off for longer each night.
Why Running Grow Lights at Night Can Improve Temperature Control
Timing your grow lights to switch on at night can help maintain more stable temperatures inside your indoor grow room or hydroponic setup.
Ambient temperatures naturally drop overnight. Because LED grow lights still produce some heat, running them during cooler night hours can help offset this temperature drop and maintain a more consistent growing environment for plants.
This is especially useful during colder months, when overnight temperatures can slow plant growth or create unwanted fluctuations inside grow tents and indoor grow rooms.
Running grow lights at night and switching them off during the warmer daytime hours can also help prevent excessive heat build-up. During the day, ambient temperatures are usually higher, especially in enclosed indoor growing spaces. Turning grow lights off during this period reduces strain on ventilation and cooling systems while helping stabilise grow room temperatures.
More stable temperatures can assist with:
- Healthier plant growth
- Reduced plant stress
- Improved nutrient uptake
- Better humidity management
- More consistent hydroponic growing conditions
Lower Electricity Costs with Night-Time Grow Light Schedules
Another major advantage of running grow lights at night is reduced electricity costs.
Many electricity providers in Australia offer off-peak energy pricing, where power usage during night-time hours is cheaper than during peak daytime periods.
Because grow lights are one of the largest power consumers in an indoor hydroponic system, operating them overnight can help lower overall running costs, particularly for larger grow rooms using high-powered LED grow lights.
By combining automated grow light timers with off-peak electricity rates, indoor growers can improve environmental control while also increasing energy efficiency and reducing operating expenses.
Automate Your Grow Lights at Night
Many modern indoor grow light systems make it easy to provide hydroponic plants with the right balance of light and darkness.
Timers can be connected to automate lighting schedules and ensure consistent grow light exposure.
Some grow light systems can also connect to mobile phone apps, allowing remote control of on and off times for sunrise and sunset settings.
Compatible grow lights may also offer light dimming through mobile app controls.
Looking for an Automated Grow Light System?
If you want an easy way to turn grow lights off at night, A-Grade Hydroponics can help.
At A-Grade Hydroponics, we are indoor growing experts and stock a wide range of grow lights and lighting systems, including automated timers with mobile phone app connectivity.
Check out our online hydroponic store, visit our Melbourne shop, or call (03) 9555 6667 to discuss the best grow light options for your indoor hydroponic setup.
