HID grow light systems don’t have to be complicated. Follow our simple guide to choosing the best setup for your hydroponic garden.
H.I.D. stands for High-Intensity Discharge. And intense, it is! These special lights have been used for decades in large commercial greenhouses. But now they are readily available for home use. HID lighting systems have revolutionized indoor gardening… What a vast improvement for the modern home hydroponics enthusiast (that’s you)…
HID grow light systems are pretty much the standard now for an indoor vegetable or medical herb garden. They are fairly expensive and hot, but they supply the proper spectrum needed for flowering and fruiting crops. Actually, they are quite close to what the sun provides.
Table of Contents
HID= MH & HPS
There are 2 types of HID bulbs available:
- MH (metal halide)
- HPS (high-pressure sodium)
The MH is a good all-around light, and perfectly adequate for most vegetables. If you can only afford one light, get a metal halide (MH). You can get a good 400 watt MH lamp with bulb for under $100 (most of the time).
The HPS bulb is preferable for the flowering/fruiting stage of your vegetables. Preferable, but not absolutely necessary…
Hmmm… MH is best for the vegetative growth stage, and HPS is preferred for the flowering/fruiting stage… Decisions… decisions… Hold on now… there’s an easy solution!
Get a lamp that will accept “conversion” bulbs! Use your MH bulb during the vegetative growth stage, and switch to the HPS bulb after the flowers appear. Voila! The best of both worlds… and simple, don’t you think?
HID lighting systems have gotten much more compact and come way down in price in recent years.
Although HID bulbs are pretty expensive, they last for years.
- MH bulbs will last for two years, but we suggest you change them at 12-14 months (of daily use; don’t forget to deduct the time you were using the other bulb).
- HPS bulbs will last up to five years, but you should change them every two. Why? HID bulbs will keep on lighting, but they gradually lose their spectrum (and effectiveness). And you can’t tell just by looking at them. But your plants will know…
4 Parts To The HID Grow Light Systems
We recommend that you buy the hood, ballast, and bulb together, so they are all compatible. You must match the ballast to the lamp and bulb wattage: you can’t use any old ballast you might find lying around in the garage. And you can’t switch to a different bulb wattage later, either. The lamps & ballast are made to be used for only one wattage of the bulb.
Modern HID lighting systems have 4 components:
- Reflector Hood – The least efficient is the parabolic or cone-shaped. Best coverage with the Wing or 4-sided rectangular hood. These also work better for light movers.
- Remote Ballast – (The power box) Get it up off the floor, so it won’t get wet. You must match the ballast to the bulb wattage. Do not buy a grow light with the ballast inside the lamp assembly. Too hot and too heavy! If using a tent or grow closet, put the ballast outside if possible… It’s a HOT little beast.
- Bulb – 400-600 watt are the most popular. Conversion lamps allow you to use both bulb types (HPS & MH) for all types of plants.
- Timer – Heavy duty grounded (3-prong-plug). Get the manual (pin) type with 2 plug-ins. This way you can time 2 lamps at once. Don’t get an electronic timer, you won’t need it and it breaks down easily.
- Light Mover (optional) – Serious about your hydroponics setup? A light mover system will kick it up a notch.
Do you need an air-cooled lamp?
Okay, so by now you probably know that you want a conversion lamp with both an MH bulb and an HPS bulb. And you know you will need a good reflector, a heavy-duty ballast unit, and a grounded timer.
If you are setting up your garden in a small or closed off room, you should give serious thought to getting a lamp with exhaust ducts and an inline fan, so you can route the heat out of the grow-room. This will definitely cost more, but you will not be fighting the heat! A cheap oscillating fan will not get rid of 94-degree heat in a tiny little grow room.
Unfortunately, this is a decision you need to make NOW before you buy your HID lamp. Why? If you opt for a ducted lighting system, you need to order a lamp with cutouts on the ends which allow exhaust duct hookup.
They look like this:
And this is what they look like with the ducting in place:
You will also need a small round exhaust fan inline in the ducting to push the heat created by the lamp out of the grow-room. Just so you know… something to think about. These are called “air-cooled” lamp systems, and may well double your lighting costs.
We have not had to resort to inline exhaust ducting, but our gardens have always been set up in fairly large rooms with plenty of A/C, or on a cool patio. But if I was going to set up in a small enclosed area, I think I would get an exhaust duct/fan system.
What about wattage?
Okay now, what wattage do you need?
- 25 watts per square foot of garden as a minimum
- 30-50 watts per square foot is preferable
- You can’t have too much light, but you sure can have too much heat!
- 16-18 hours per day vegetative growth
- 12-14 hours per day flowering & fruiting stage
- Total dark when lights off!
Maybe this nifty chart will help:
- 400 & 600 watts are the most popular hydroponic grow lights
- 400w HPS is the most efficient & versatile HID lighting system made
- 1,000 w bulbs are very hot and can’t be placed very close to the plants. Get two smaller ones instead or install an inexpensive light mover to make the most of all those watts.
Is my garden getting cooked?
Here’s how to check for excess heat:
- Place your hand palm down right at the top of your plants.
- If the top of your hand is hot, you need to raise the lamp higher.
- But if your hand is pleasantly warm, that’s just right. You want the light as close as possible without burning the plants.
How much will the HID light raise my electric bill?
Answer: From $7- $20 per month, depending on what you pay per KWH. If you run a 400-watt lamp 18 hrs per day, you will use 7.2 KWH per day. Check the cost per KWH on your electric bill and multiply X 7.2 X 30 to get the approximate operating cost per month.
Help! No matter what I try, the HID light tilts down at the cord!
Solution: Put a brick (or other heavy non-combustible weight) on top of the lamp, and slide it over ’til the lamp is level… Voila!