Indoor Plant Grow Light Guide

Grow lighting systems allow you to extend the growing season by providing your plants with an indoor equivalent to sunlight. This is a great advantage for those of you who appreciate having a year-round supply of fresh flowers, veggies, and herbs. Artificial lighting is also a great way to jump-start spring by starting your seedlings months ahead of the last frost.


HID (High Intensity Discharge) Plant Grow Lights

HID lighting is one of the most efficient ways to provide light to plants and one of the most economical because they can cover a large area with a single fixture. There are two types of HID grow lights used for horticultural lighting:

MH Plant Grow Light - ACF
Metal Halide - MH

Metal halide bulbs produce an abundance of light in the blue spectrum. This color of light promotes plant growth and is excellent for green leafy growth and keeping plants compact. It is the best type of light to be used as a primary light source (if no or little natural sunlight is available). The average lifespan is about 10,000 cumulative hours. The bulb will light up beyond this time but due to the gradual decline of light, it is not worth your while to wait for the bulb to finally burn out. If you compare their lumen (brightness) per unit of energy consumed, metal halides produce around 125 lumens per watt (up to 6x the lumens per watt compared to with standard fluorescent lights and incandescent bulbs).


High Pressure Sodium - HPS
HPS Plant Grow Light
High pressure sodium bulbs emit an orange-red glow. This band of light triggers hormones in plants to increase flowering/budding in plants. They are the best grow lights available for secondary or supplemental lighting (used in conjunction with natural sunlight). This is ideal for greenhouse growing applications.

Not only is this a great flowering light, it has two features that make it a more economical choice. Their average lifespan is twice that of metal halides, but after 18,000 hours of use, they will start to draw more electricity than their rated watts while gradually producing less light. HPS bulbs are very efficient. They produce up to 140 lumens per watt. Their disadvantage is they are deficient in the blue spectrum. If a gardener were to start a young plant under a HPS bulb, she/he would see impressive vertical growth. In fact, probably too impressive. Most plants would grow up thin and lanky and in no time you will have to prune your plant back before it grows into the light fixture. The exception to this is using HPS grow lights in a greenhouse or in conjunction another light source that emits light in the blue spectrum. Light sources that have a high output in the blue spectrum like sunlight and MH grow lights offset any stretching caused by HPS bulbs.


Fluorescent Plant Grow Lights

ACF flourescent grow lights CFL (compact fluorescent) and T5 full spectrum fluorescent lights are an excellent low cost option for lighting small areas indoors. At 75 to 90 lumens per watt, these lights are energy efficient and extremely effective especially when used in numbers. Fluorescent grow lights also have better color rendering properties (more of the light emitted is used by the plant) and produce much less heat than incandescent and HID grow lights. This allows them to be placed closer to plants (within a few inches) greatly decreasing light loss from the bulb to the plant. It is recommended that these lights be placed no more than a couple feet from the plants for best results. 2700k to 3000k bulbs provide higher output in the red spectrum which promotes flowering. 5000k to 6500k bulbs are full spectrum with much of the light in the blue spectrum which promote overall green plant growth.



LED Plant Grow Lights

LED grow lights LED grow lights are the newest lighting option for plants. They have come a long ways from the days of blue and red bulbs and are now available in full spectrum natural looking lights that blend in with the surroundings. LED lights are also among the most efficient and coolest running grow lights available. We offer LED grow bulbs that are compatible with standard household light sockets and ones for T5 HO fluorescent fixtures. We offer them as replacement bulbs to upgrade your existing fixture, or as a complete system. They perform as well as or better than equivalent fluorescent lights while using less electricity and lasting over twice as long.


Incandescent Plant Grow Lights

plant grow lightsThese lights are the most inefficient type of light and a poor source of light for plants. At best they can provide supplemental light to individual house plants. Incandescent lights have a low lumen output per watt compared to other grow lights and produce considerably more heat. New smaller CFL grow lights like our Green Thumb system and indoor LED lights produce as much light as a 200 watt incandescent bulb with less than 1/4 of the electrical usage, and more of the light is used by the plant. This type of bulb will pay for itself in energy savings the first 60 days of use.


Light Output Comparison Chart
ACF Plant Light Comparison Chart
Each scenario above represents approximately 50,000 lumens.
Grow Light Comparison Chart
Grow Light
Watts
Growing Area
Heat Output
Recommended Light
Height Above Plants
Bulb Life
(hours)
Primary
Secondary
LED bulb
23
1.5' x 1.5'
2.5' x 2.5'
Very Low
3" to 1.5'
25,000
CFL bulb
40
1' x 1'
2' x 2'
Very Low
3" to 1.5'
10,000
CFL bulb
125
2' x 2'
3' x 3'
Low
6" to 2'
10,000
2' T5 (single) FL
24
1' x 2'
1.5' x 2.5'
Very Low
3" to 2'
20,000
2' T5 (single) LED
21
1' x 2'
1.5' x 2.5'
Very Low
3" to 2'
50,000
2' T5 (2 bulbs) FL
48
1.5' x 2.5'
2' x 3'
Very Low
3" to 2'
20,000
2' T5 (2 bulbs) LED
42
1.5' x 2.5'
2' x 3'
Very Low
3" to 2'
50,000
2' T5 (4 bulbs) FL
96
2' x 3'
3' x 4'
Low
6" to 2'
20,000
2' T5 (4 bulbs) LED
84
2' x 3'
3' x 4'
Low
6" to 2'
50,000
4' T5 (single) FL
54
1' x 4'
1.5' x 5'
Very Low
3" to 2'
20,000
4' T5 (single) LED
41
1' x 4'
1.5' x 5'
Very Low
3" to 2'
50,000
4' T5 (4 bulbs) FL
216
2.5' x 5'
4' x 6'
Low
6" to 3'
20,000
4' T5 (4 bulbs) LED
184
2.5' x 5'
4' x 6'
Low
6" to 3'
50,000
4' T5 (8 bulbs) FL
432
4' x 6'
6' x 7'
Low
1' to 3'
20,000
4' T5 (8 bulbs) LED
328
4' x 6'
6' x 7'
Low
1' to 3'
50,000
HPS
250
3' x 3'
5' x 5'
Medium
2' to 3'
24,000
HPS
400
5' x 5'
8' x 8'
High
3' to 4'
24,000
HPS
600
6' x 6'
10' x 10'
High
3' to 4'
24,000
HPS
1000
8' x 8'
12' x 12'
Very High
4' to 6'
24,000
MH
250
3' x 3'
5' x 5'
Medium
2' to 3'
10,000
MH
400
5' x 5'
8' x 8'
High
3' to 4'
10,000
MH
1000
8' x 8'
12' x 12'
Very High
4' to 6'
10,000
Growing Area
The growing areas listed above assume the light bulbs are being used in a fixture
with a reflector similar in quality to the ones offered on this web site.
Primary - Use the area in this column if the grow light will be the main or only source of light for the plants. This includes areas where minimal light comes Property of ACFgreenhouses.comfrom windows or standard house/office lights.
Secondary - Use the area in this column if the grow light will be used in a greenhouse or other area that receives direct sunlight for part of the day to supplement the light from the sun.
Heat Output
The chart above uses a combination of the light bulb temperature and the dimensions of the bulb(s).
Bulb
Average Bulb Temperature
.
Bulb
Average Bulb Temperature
T5 (LED & FL)
100 to 120° F
Incandescent
220 to 260° F
CFL
130 to 180° F
MH/HPS
450 to 550° F
ACF Greenhouses Grow Light GuideHow Long Should Grow Lights Run?
This depends on the type of plant. Foliage plants need about 14-16 hours of light per day. Flowering plants need 12-16 hours of light per day. You should give most plants at least 8 hours of total darkness daily. Try to have the lights on at the same time every day. You can get an automatic timer for your lights to make it easier.
ACF Greenhouses Grow Light GuideThe Electrical Cost to Run a Grow Light System
To get the operating cost per hour for a light, take the lights combined wattage, and divide it by 1000 to get the kilowatts used. Then multiply that number by the amount your electric company charges per kilowatt hour. HID lights will use the number of watts it emits per hour, ie; 600w system will use 600 watts per hour (regardless of spectrum).
(light wattage output / 1000) x electricity cost per kilowatt hour = Operating cost per hour
operating cost per hour x hours used per month = Operating cost per month