I'm pretty sure a 150w hid still outputs the same heat as a 150w led or 150w halogen or incandescent.. it is the efficiency of the light that allows you to run less wattage which means less heat. In addition the direction the heat is emitted is different with LEDs
I was surprised when I learned this too, be nice though that is a bit rude the way you are talking IMO, especially when you are wrong. You need to do a little homework on this I think. Btu`s per watt of electricity is constant , the efficiency of the light produced is what changes look it up
Just to set the record straight with my rudimentary understanding of physics, all energy is eventually converted to heat.
150W is 150W and that energy will be released in three forms: convective heat, conductive heat, and radiated heat. Radiated heat takes the form of any electromagnetic wave – including visible light and infrared. Infrared is different to visible light, as it has a frequency that interacts with water molecules that transfers its energy very quickly, but they are still both electromagnetic waves.
That means we feel "hotter" under infrared light because the radiation interacts with our water molecules (similar to a microwave oven) that leads to a fast build-up of energy (heat). Visible light also interacts with our molecules, but most of it is reflected, which means a lot less energy is transferred in the same amount of time. But eventually visible light will be absorbed by each surface it hits and raise its temperature incrementally until all the light is absorbed. Infrared is just absorbed quicker in water.
LEDs emit more radiation in the visible (and PAR) range compared to HIDs. HIDs emit more radiation in the infrared range. LEDs also emit conductive and convective heat, which is released into the atmosphere via anything that touches it, including a heatsink (conductive) and then the air that blows over it (convective). HIDs also emit conductive and convective heat (from the bulb).
Plants absorb light and that energy drives photosynthesis and is stored in the plant. But eventually all that energy is released when the plant dies and the wood composts or burns (exothermic reaction).
What all this means is, 150W of LED will eventually be converted into the same amount of heat as 150W of HID. But HIDs will transfer more heat through infrared radiation that warms the plant's water molecules, whilst LEDs will transfer more photosynthetic energy in the form of PAR that is used for photosynthesis. So a LED will drive more photosynthesis for the same amount of wattage as a HID, and a HID will increase leaf temperatures more than an LED.
The final piece of the puzzle is that any visible light that is not absorbed by the plant will also increase leaf temperatures – that energy is not captured and stored by the plant via photosynthesis, so it starts to vibrate the water molecules in the plant which "heats up". Heat is just a measure of the active state of a molecule, which can be passed on to other molecules. What we fell as "heat" is just a transfer of energy.
A complete and balanced photosynthetic spectrum will drive more photosynthesis with less leaf temperature increase than a narrow spectrum that bombards the plant with high amounts of certain light (blue for example) that cannot be fully absorbed. So even amongst LEDs, a full spectrum will transfer less initial "heat" than a narrow spectrum. That is the simplest explanation I can think of.
