Add a 450W LED to two 300W LEDS or a 250W HPS?


I have a 3’ x 3’ tent with two 300W LEDs. I believe that is not enough to get through flowering. Not sure if I should add a 250W HPS or a 450W LED. Would appreciate your thoughts.


time for the cob led upgrade


IMO go led.

I have a 300 hps and a 600w led in a 32"-32"-53" tent and the led is kicking butt. Hands down I’m going all led and taking out the hps. I can get the led light closer to the plant and that’s a plus for me. And temps will be way easier to control.


It really comes down to how well you’re able to manage canopy temps with hps. People have been growing top shelf weed with it for a long long time. Initial cost is low, and you could see some added value with the blending of light spectrum. If temps won’t be an issue, one could put up a good argument for going hps route.

If there’s any chance at all you will have trouble managing temps, then go with led. Assuming you have mars, galaxy, viparspectra, or any of those type of 300w lights from amazon, people seem to like around 3 of them in that size area. Bumping one up to the next size or 2 shouldn’t create any issues.


@Wishingilivedina420state @dbrn32 Thanks for your input!

It would seem I need to do an experiment with my lights. My tent is in the basement, I live in cold climate, and I don’t plan to grow during the summer. Temperatures in the basement at night in the winter can get into the 50s. So, I am not sure I won’t have the opposite problem that most do with temp control. Right now, with temps in the basement getting down to about 65 degrees the tent temp at grow level is about 68 degrees. During the day and evening, it stays pretty steady at about 75/76 degrees. This is all with one 300w LED. So, pretty good I think. However, it is not winter. I likely need to wait just a bit for it to get a little colder and see what happens when I turn the second light on (using just one since they are still seedlings).

While I may change my mind if I feel I need heat, I am actually now leaning towards two 300w Viparspectra LEDS. this would give me around 60w (tru) per sq. ft. and it would evenly distribute the light as I have a square tent. Also, it would make managing the temp in the spring when I will be flowering easier. However, @dbrn32 HPS is tried and true.

On a side note, regarding rated watts and true watts. It seems to me that the plant is converting energy. True watts is actual energy. LEDs would have to be SO much more efficient at converting energy to light to make up the difference between true watts and rated watts. While I believe they are more efficient (that is obvious since they don’t emit as much heat, which is energy), I am skeptical that they make-up the difference. So, while four 300w LEDS equals 1,200w the actual energy is something around 135w x 4 = 540w. That would give me 60w per square foot. I think that is a great number as I feel it is approaching overkill unless you go hydro and can supply all the nutrients and CO2. With three it would be at 45w sq. ft., which is a little short according to the standard 50w sq. ft.


@Medforme this is where the confusion starts to set in with led’s.

The rating of the light is based on the max output of the bulb times how many bulbs : not it’s actual output. They are never driven at max because they are most efficient at around 30% of their rated output. So one should always go by the plug value rather than the stated output.

IMO experience with led’s you can get very close to them and can grow some dank ass stuff. I got 1.25 pounds from 2 plants that were exactly 4 months old. In soil.

35 to 50 watts per is the metric. 35 being the value for led’s and 50 watts per square foot for MH and HPS.

As for heat, you can always add heat. I think you are in a good place. In the winter my grow box receives supplemental heat with a 300 watt aquarium heater immersed in a 5 gallon bucket of water. Works fantastic.


You got it, more or less.

Like @Myfriendis410 says, some manufacturers choose to advertise their light like this…“1000w one hundred 10 watt diodes” usually the 100 ten watt diodes is a true statement. But not the 1000w. To be 1000 watts, all 100 if the diodes would have to be driven at max current. For a 10 watt diode it’s usually 3-3.5v at 3amps. As myfriendis also said, you probably won’t ever see that. Nor would you really want to. With all leds, as the drive current goes up the efficiency will go down. Some are more efficient than others, by a bunch. But that’s usually where you see prices start to go way up.

Another thing to keep in mind is driver efficiency. If you’re running 600 actual watts, you could start to see some gains in the driver category as well. The best are usually in the neighborhood of 93-95% efficient. But a lot of them used in budget lights are as low as 80% efficient. If you’re talking 15% in efficiency loss over 600 watts, that’s like 100 watts coming from your wall that isn’t producing light.

Getting off topic a bit there, sorry. To be honest, if you don’t plan on growing during warmer months hid may be your answer. I’m led guy personally, but hid could help in your situation. If you decide to go that route, I would suggest checking out lec (light emitting ceramic). It will get you a little better efficiency than hps, has some spectrum benefits, and is typically found to between led and hps in canopy temps. The 315 models would essentially be a perfect fit for your tent too. Perhaps @Donaldj could weigh in, as he uses them.


@dbrn32 @Wishingilivedina420state Found some very highly rated 150w HPS lights, so I could use two and get the better light coverage I want. However, they cost almost as much as 300w LEDs (CELs were much more expensive) and will not last nearly as long, although you only have to replace the bulb ($15.00) instead of the whole light as with LEDs. So, cost is probably similar enough not to be an issue. Looks like it comes down to temp control.

@Myfriendis410 I love the aquarium heater idea! I am assuming that I will have humidity issues (too dry) in the winter, as I suspect you do. It would seem your solution would help with this as well. On the other hand, you could be pumping 300w into a light giving off heat, but then you may still have a dryness issue. Is dryness an issue for you?


Low humidity can be an issue during veg in the winter but not for flower so much. Remember that the heater is only running to maintain temp in 5 gallons of water which is a considerable thermal mass. Once it’s at temp maintaining it is cheap. It’s not like the heater is on nonstop lol.

@dbrn32 is a fantastic resource on lighting. I always listen closely to him. In general though, more light the better. You’ll never achieve sunlight equivalent realistically.


Led for suer


lol, yes this may be true, but it doesn’t keep me from trying.


@bryan me too. I need sunglasses in my grow box haha.


You can come pretty close to replicating the par levels and color spectrum from uvb to ir of the sun. You won’t be able to do it without a lot of cash though, and then you’ll most likely be short of the naturally occurring aspects of a grow.

For all intensive purposes, we’ll say that it’s just not economically feasible to do so. You can do pretty darn well indoors by following standard grow strategies for much cheaper.


Decided to go with at least one additional 300w LED (Viparspectra). I will decide on any additional light later as I do not need it for now.