LED advice needed


A question from a fellow grower:

I have 3 sour diesel 3 bubble gum 3 AK 47 and 3 ak47 autoflower from you and a mystery plant .
I have 1 300 watt led not and 15 23 watt cfl. I need to get more leds should I get a 600 watt led or 2 more 300 watt led?
I wanted to use the leds for veg and flowering.
I picked leds due to heat and elec bill.


As to how much light you need, it depends on the size of the plants or the total area. You might have enough for your size area. Also when discussing LEDs, I need to know the actual watts the LED uses and not what it is called. A lot of LEDs only use actually half or maybe even less wattage than what they are called. If the 300 watt LED is using 60 x 5 watt LEDs, or maybe 100 x 3 watt LEDs, the manufacturer might call it a 300 watt, but each LED is only safely driven to about half the max power it is rated for and so that LED might be only really using 150 watts or less.


What do you think my harvest will be with for NL autos, 400watt led in 27" by 27"× 63"? Also how close should light be to plants?


Most LEDs have a sweet spot at about 12 to 18 inches away from the leaves, but I’d check the manufactures recommendation.

What kind of 400 watt LED? How many actual watts does it use?


so a 300 watt led that’s has 100 3 watt leds is or could be only 150 watt?


Yes, you are correct, the 3 watts is the max they could possibly be driven at, but most manufactures of LEDs do not recommend driving them to much more than about 50% capacity. Maybe 75% max, and so you could use a watt meter or check with the manufacturer so you can compare actual watts to actual watts when shopping prices or comparing to HID lights that do use actually as much watts or maybe a little more with the ballast, than the labeled name watts.

So yes, a 300 watt LED may only be using 150 actual watts, or maybe slightly more, and a 400 watt HID might be actually using a bit more than 400 watts, say maybe 425 or 450 watts with the ballast.


well sir it costs 35$ to run 4 300s per month just got my new electric bill


and?.. What does that mean? LEDs are known to save electricity, but your bill is not an indicator of actual watts used. Unless you want to show all the math, price per kilowatt hour and what your kilowatt usage was before using your lights and after, and the log of how many hours you ran them per day.

It seems it would be easier to figure out how much they are using by contacting the manufacturer or plugging it into a kilowatt meter plug, you can usually find them around $20 on amazon:


that was for running 12 on 12off for 30 days’ I have checked and they are running at 165 watts each


Sounds about right, just a little more than 50%, a little of the extra watts might be coming from the fans that cool them.


yes sir they have 2 fans on each light


So about 660 watts at 12 hours per day only cost you about $35 more on your electric bill. I’m sure this is information that can be helpful to many. :smile:


Can 2 kind k5 - 1000w led grow light be Compared with electrical usage (inside a house) for one month use…?



According to the stats on your light as found by @LeStat in your other inquiry,

So you have maybe just 10 watts less per light than the total light described above. So if 660 watts cost them about $35 more a month on their electric bill, and if your utility charges about the same rate, then your cost might be double that, right?

650 watts x 2 lights=1300 watts

calley had:
660 watts equaling about $35 a month on the 12 hours on per day schedule.

$35x2=$70, so all thing being equal, your bill would probably be about $70 more a month running your light 12 hours per day. Make sense?



ok thanks, but do you know which light is best for “gorrila grow tent 2x2,5x5” 11 "I just want to grow mother plants in the tent …?


Hey mate, a followed 1 of your links that had the top 5 led lights for under $200, or cheapest 5 led lights or something long those lines, and I have searched and searched and cannot find it! I put a power consumption thing on the 300w led I bought to find it only consumes 84w! It is currently in a 2x2 tent, and 1 week into flowering. However I have purchased a 4x4 tent which will arrive in n the next few days so from what I’ve read, I’ll be wanting atleast 500 true watts, which is actual watt consumption isn’t it? Any help be much appreciated :slightly_smiling:thanks


I’m not sure what you are talking about. I do not endorse any specific name brand LED and am unaware of such a list, I don’t believe I myself have ever posted any links like that.

Most LEDs will at least use about half the wattage, so most LEDs that say they are a 300 watt LED is because they are made of 100 x 3 watt LED diodes, or maybe 300 x 1 watt LED diodes, but that is the max the diodes can be run at until they burn out, and so most LEDs are only run at about 50% or maybe only slightly higher than 50% of their max capacity.

And so a LED that says it is a 300 watt but only really uses approximately 84 watts seems like it is probably a very poorly made LED.

Happy growing,



Sorry I thought it was 1 of them your posts, u are definitely the LED specialist and there was a topic that had links to some LED lights on Amazon. Most the cheap LED’s seem to consume 25-30% of what the light is listed as! I see you have a custom rig, would it be easy to put better LED’s in my light? Would you trust the coverage area listed on the cheaper lights, or would you go off 35 true watts per square foot?
Thanks again


Well, I don’t know the specifics of what your light is made of, but the total watts is actually regulated by the driver. The driver can kind of be thought of as the ballast in a HID or maybe even a fluorescent light. It’s a transformer that usually transforms the standard AC current to most often DC current, but some LEDs run on AC current, but either way, the total voltage and amperage is converted and regulated to drive the LEDs at an appropriate level.

You might be able to drive the LEDs at a higher power by replacing the driver, or drivers, or you might be able to use the drivers in the unit to drive more efficient LED units. It could depend on many different factors.

Here is an interesting you-tube video where “growmau5” (pronounced Grow Mouse) does use a somewhat cheaper LED system, a MARSII Hydro LED and upgrades the LEDs in it, and this tutaorial, and his other tutorials might get you what you are looking for: