Led = leggy plants.

[Bud goode]

Hi folks. I was thinking of moving to led, yet when I see plants grown under them they look very stretchy, especially seedlings. My hps dual spec produces seedlings that rarely stretch longer than an inch or so before true leaves show. The original idea was to save on electricity without compromising my yield. But I've since read that studies have been carried out that claim the saving isnt as much as people think. Is this just an attempt by hps light dealers to discredit led or truth ? What are your views on this ?

[Easy-T]

I've found Definitely cheaper to run, you've just got to find their sweet spot to stop them over stretching

From behind the bushes

[Max - LEDTonic]

Generally, plants will stretch excessively from higher temperatures, low light intensities, and red-dominant light (low kelvin) or far-red wavelengths (shade-avoidance response).
Although, a high-intense, low-kelvin light can produce more compact plants than a low-intenste, high-kelvin, as light intensity can trump spectral composition.
HPS lamps emit a lot of red and far-red light, but also often produce very high light intensities. They emit very little blue light (3%?), and blue light works in the opposite direction, making plants grow more compact. Generalizing a fair bit, LED lamps typically emit between 10-20% blue light.

If the light intensity is the same in both experiments, an LED lamp should produce more compact plants than an HPS, as it has more blue light and no far-red light.

Bruce Bugbee has done a lot of experiments and studies on different wavelengths and how they affect plants.
Here's a good video if you want to dive deeper:


LED lamps are oftentimes more efficient than HPS lamps and fewer watts will be needed to reach the same light intensity.
It isn't black and white as both HPS lamps and LED lamps varies in efficacy.
A high-end 1000w DE HPS lamp produce upwards two times as much light per watt [1.7-2.0 µmol/J) as a small 250w SE HPS bulb does (0.8-0.9 µmol/J).

Generalized, the most efficient LED lamp (3.0 µmol/J) is three times as efficient as the lowest quality LED lamp (1.0 µmol/J).

Here's a good video from AlboPepper that explains efficacy with different lamps as examples. Not all sellers are honest and it's easy to manipulate numbers.
To avoid buying a pig in a poke, one must understand the tech and know what to look for.

[Farmer Geddon]

There's a grower here that raised his Mars led because they weren't stretching enough.

[LEDTonic - Daniel]

Adding to Max's points, your electricity savings will be the result of the less watts consumed.
If you're running a 600W HPS and replace it with a 300W LED, then you'll halve your electricity usage. It'll come down to your electricity cost ($/kWh) how much you'll end up saving in real monies.

I believe the average kWh cost is around $0.13 in the US. If this is what you pay then apply the following calculation to calculate electricity savings:

kWh cost * kWh usage * photoperiod (number of hours you run your lights) * duration (days)


If you want to calculate your savings per month (30 days) and assuming you replace a 600W with a 300W lamp and assuming you run your lights 12 hrs you get the following numbers:

Cost to run the 600W for 30 days
0.13*0.6*12*30 = $28.08

Cost to run a 300W for 30 days:
0.13*0.3*12*30 = $14.04


The question you should ask yourself is how many fewer watts you can get by with. If you're considering switching purely to lower your electricity cost then you should consider the upfront investment of a new lamp and for how many months/years/grows you intend to run it, then you can see how much cash you save.
You'll also need to consider what LED lamp adequately fills your grow area with enough light. I assume you don't want less light than you're getting today from your current lamp.

[gardro]

Premise of OPs point needs further explanation really.

Is it spectrum?
Is it watts?
Is it stretch in first few days?
Is it stretch in general?
Is environment like for like?

In general, LED is renouned for tightly noded stocky plants so Id say those comments are from either someone highly invested in glass bulbs or someone that has no real experience of led.

A nervous, new to led grower could experience issues with dimming too much but a stopped clock is also right twice per day.

Id look at genetics before light personally

[scoot]

I switched from 600w HPS to 2x240w QB's 3500k running at 220w each so 440w compared to the 660w that the HPS was using I'll take that 220w saving in leccy!
As for stretchy it will depend on the kelvins of the light,the output of the light,and how far from the canopy it is,I haven't found plants to be stretchy or leggy under the QB's.

[Bud goode]

There's a grower here that raised his Mars led because they weren't stretching enough.

So this dude likes stretchy plants. Personally I like my close inter nodal spacing.

[Bud goode]

Adding to Max's points, your electricity savings will be the result of the less watts consumed.
If you're running a 600W HPS and replace it with a 300W LED, then you'll halve your electricity usage. It'll come down to your electricity cost ($/kWh) how much you'll end up saving in real monies.

I believe the average kWh cost is around $0.13 in the US. If this is what you pay then apply the following calculation to calculate electricity savings:

kWh cost * kWh usage * photoperiod (number of hours you run your lights) * duration (days)


If you want to calculate your savings per month (30 days) and assuming you replace a 600W with a 300W lamp and assuming you run your lights 12 hrs you get the following numbers:

Cost to run the 600W for 30 days
0.13*0.6*12*30 = $28.08

Cost to run a 300W for 30 days:
0.13*0.3*12*30 = $14.04


The question you should ask yourself is how many fewer watts you can get by with. If you're considering switching purely to lower your electricity cost then you should consider the upfront investment of a new lamp and for how many months/years/grows you intend to run it, then you can see how much cash you save.
You'll also need to consider what LED lamp adequately fills your grow area with enough light. I assume you don't want less light than you're getting today from your current lamp.

I've been told 300 watts is not enough for 1.2 x 1.2 grow grow tent. I can't remember what wattage was recommended. When him and me worked it out before I'm sure it was above 1000 required. Thanks for your input friend.

[Bud goode]

I switched from 600w HPS to 2x240w QB's 3500k running at 220w each so 440w compared to the 660w that the HPS was using I'll take that 220w saving in leccy!
As for stretchy it will depend on the kelvins of the light,the output of the light,and how far from the canopy it is,I haven't found plants to be stretchy or leggy under the QB's.

Yours look great my friend.. Definitely not leggy. Thanks for your input Scoot.