E-mail -- LED vs HPS

Hello Dr. E.R. Myers,

I would like to thank you for taking the time in providing everyone with all the knowledgeable information that is posted on HTGSupplysaskthedoc. I read your posts more then the daily newspaper. I am new when it comes to ordering from HTG Supply but I am quickly becoming a loyal customer.
My question is...
Which would you (personally) use between a 90 Watt UFO LED or a 400 Watt HPS for flowering? I am torn between the two. I know there are pro's and cons to both but am I just going to be disappointed if I try to flower with a 90 Watt UFO LED? The area (enclosed) where either light will be used is 4' x 4' x 7' feet tall. Also, what is the minimum and maximum square foot coverage you would use for both?
Hope to have a reply from you soon and thanks for all the input you provide

Hello,
Thank you so much for the kind words. I really hope I am helping people be better growers. I know I am enjoying hearing and learning from people like you. The best compliment is telling a friend. (I read that at my dentists office)

I personally would go with the HPS for flowering. I should say I am just getting into using LED's and have used HPS's forever. I will be writing about LED's in the next few posts. ( Link to first part of LED test) I know you can grow plants with the triband from HTGSupply.com but an HPS would be better if you can handle the heat. LED tend to have a more focused light, meaning it comes straight down. the HPS if it has a good reflector will bounce MORE light around a LARGER area.

If you have issues with heat, or electricity usage (400w vs. 90w) then you should go with the LED (or maybe two in that area which still has less heat and electricity usage). Otherwise I think you will be very happy with a 400W HPS in a 4x4 space. You do have some sort of ventilation to get rid of the heat right? If not, you may want to think about a 250 W HPS. I think even this would be a bit better than one 90 W LED for flowering.  Even leaving the door to the closet/grow room open with a fan when the light is on should be enough to keep the temperature below 100F (which is when most plants are very stressed). With the 7 feet of height you can keep an HPS a few feet above the plants. You could grow short plants and keep the HPS further away (use mylar etc.) and this may keep the temperature by your plants down. If the HPS is too close you will see the closest part of the plant turn brown, due to heat stress. If you can, buy a thermometer with a Min. Max feature and make sure the temperature by the plant tops (closest to the light) does not go over 100F. The 90's are a bit high but ok. Ideally you want the day (lights on temperature) to be in the 80's and night in the 60's for most plants.  I hope this helps.

Please read my latest post about LED vs. HPS

Good Growing,
Dr. E.R.Myers

p.s. In general you want at least 1000-1500 lumens per square foot, and you can go up to 3000 lumens per square foot.