Quote Originally Posted by Roughrider
Although I'm still kind of a new poster, I keep seeing a lot of the same comments--many of which are answered an Dr. Khronik's excellent El Cheapo Guide to Lighting. But there are a few things I'd like to add in regard to watts, lumens, cfl, hps, and efficiency and how much light you need. Maybe this should be stickied?

Watts have nothing to do with light or growth. Watts measure how much power a light fixture uses to produce light. You can tell how efficient a light bulb is by looking at watts. A 23 watt CFL produces as much light as a 100 watt incandescent...even though the incandescent has more watts, it's useless. See what I mean?

What you care about is light...more specifically, light energy. That's what plants use during photosynthesis/growth. Light is measured in lumens. In my experience and reading, lumen amounts per sq. ft./sq. m. look like this

2000 lumens sq. ft./21500 lumens sq. m. = Absolute minimum for growth. You won't get much from this, especially after the plant has grown a bit. Not really enough to flower well.

3000 lumens sq. ft./32250 lumens sq. m. = Pretty Good growth. Enough light for the entire light cycle, although your yields may be lower.
4000 lumens sq. ft./43000 lumens sq. m. = Very good growth. Once you pass around 3500, growth rate and ability goes up fast.

Over 5000 lumens sq. ft./53750 lumens sq. m. = Optimal growth. Dense growth in all stages.

Keep in mind that using reflectors, using mylar or having flat white walls, and keeping your lights close to your plants keep you from wasting lumens. It's not just about having light, it's about getting the light to your plants. IMO, people ofter overbuy lights. This creates more light, but the light isn't always hitting the plants. And that creates more heat and ventilation issues, which causes stress problems.

That's why it's still impossible to tell anything about growth or yield based on just lumens. A guy that has an HPS that is too far away from plants that have no walls near them and no ventilation may get poorer results than a grower with CFLs that uses reflectors and has a couple of lights under the canopy in a well-ventilated spot.

HPS lights are often said to generate more heat than CFLs. That's not really true...it's just that they are more efficient at producing light, and there's a smaller surface area on the bulb itself for the resulting heat to dissipate. That means more ventilation. But the higher amount of lumens per watt means you use less power and get greater light penetration through your canopy. Still, I'm a believer that well used CFL's can give you great grows with less ventilation and heat issues. If you're in a small to very small area (less than 4 sq. ft./.25 sq. m.), I'd consider the advantages of CFLs in that way.

But HPS is more efficient. A typical 250 watt HPS bulb/unit will produce about 27,000 lumens. I've seen people use a 250w in a 3' x 3' room and get good results. That's 9 sq. ft. which = 3000 lumens a sq. ft. (Really, a 250w HPS is better in a smaller area.) to give you an idea of the difference in efficiency of CFL vs. HPS, think of this.

23w CFL = 1600 lumens = 69.6 lumens/watt
30w CFL = 2000 lumens = 66.7 lumens/watt
40w CFL = 2600 lumens = 66.3 lumens/watt

compared to

150w HPS = 14000 lumens = 93.3 lumens/watt
250w HPS = 28000 lumens = 112 lumens/watt
400w HPS = 50000 lumens = 125 lumens/watt
600w HPS = 90000 lumens = 150 lumens/watt

So you can see that HPS is more efficient than CFL...and as you get into bigger HPS bulbs, it becomes a lot more efficient. There's also fewer hassles with multiple cords and saved money on your energy bill. If you've got a big area and/or you can deal with the heat and ventilation, HPS is the way to go in flowering. Still, I'm a believer in small HPS lights and combo HPS/CFL grows...if you've got a 2' x 2' room, you can use a 150w HPS and 4 23w CFLs from Wal-Mart and get a terrific grow with very few heat issues.

Hope this helps some people. And, yes, I wrote it all.
This is my very first post on a forum, anywhere! And your having written it all has motivated me to do so. Please forgive me if I don't follow all of the protocols but I am a quick study.

The reason I set up with this board is because one of our customers just emailed this thread to me and I thought I'd throw in with my observations as it relates to an important facet of our overall thermal management designs on the drivers which power our induction grow lamp products.

The post you've made is well written and compares two conventional grow lamp types. However I believe there are some inaccuracies in that the values posted were for initial HPS lumens rather than mean lumens which would be a better value to use as it better reflects the output over the lamp life. I've attached a link to the chart values we like to use. In respect to the efficiency getting better as the lamp gets larger, this is true up to 600 Watts, but then the efficiency decreases as you go to 750 watts and 1000 watts. Both Metal Halide and Induction lamps continue to get more efficient as they bet bigger and do not show this backward bending affect on efficiency values as HPS does.

Inda-GRO

My 30 year background is that of an Electrical Engineer with experience in nuclear and product development design engineering. Over the last year I've been working on the Inda-Gro design team and find this exciting, because so much of it stems from work that was brought to the industry by one of the most inspirational inventors of all time and that is Tesla himself.

Of course I'd like to make more people aware of the advantages of utilizing induction grow light technology I'm not here to promote Inda-Gro products as the sole solution for your particular needs since there are, from what I'm learning, many reasons that would influence the lamp choice that a grower may decide to use.

While not being a botanist by training or trade I was excited to get involved with the electrodeless induction light technology for the grower since it relies on relatively simple but delivers a high lumen/ low wattage solution for those species that demand not only proper spectrums but 1,500-1,800 micromoles saturation at the receptors to best simulate the natures energy and wavelengths.

Please feel free to call me or call me at the office should you wish to discuss anything that warrants our followup.

Thank you for your time, Jeff