What about efficiency?
LEDs are much more efficient than HPS. LEDs (reportedly) are 80% efficient (meaning 80% of the power they consume is converted to light), while HPS lights are only 30% efficient. LEDs thus require much less power to deliver an equivalent amount of light than HPS lights. This means your comparison based on the same amount of power usage is misleading. It would be better to compare the power required to produce an equivalent amount of light. A 600W LED light can produce light equivalent to a 1,000W HPS. Similarly, the greater efficiency of LEDs means far less energy is converted to heat by LEDs (20%) than HPS (70%). LEDs, therefore, feel cooler because they are cooler. They are cooler because they are more efficient. They convert less energy to waste heat.
Sorry Mate, I've got to respectfully disagree. From the web with 99.98% accuracy:
In terms of total heat energy, a true 600W LED and a 600W HPS will both ultimately produce roughly the same amount of heat in the room if you run them long enough in a closed system with no ventilation.
Here’s why:
1. Energy In = Energy Out (First Law of Thermodynamics)
A 600W light, no matter the technology, draws 600 watts of electrical power.
That energy can be converted into light, heat, or other forms, but in an enclosed space, all of it eventually ends up as heat.
Even the light energy that initially leaves the bulb or LED hits walls, plants, or surfaces, where it gets absorbed and re-radiated as heat.
So yes — 600 in = 600 out, in total energy terms.
2. Why LEDs feel cooler
HPS: Only about 30–40% of energy becomes light; the rest is heat right at the fixture (radiant + convective).
LEDs: Maybe 40–60% becomes light initially, but the rest still ends up as heat after the photons are absorbed.
Because LEDs convert more energy to light first, their fixture surfaces stay cooler and the heat is spread over time and space rather than blasting from a hot arc tube.
This is why an HPS lamp feels like a space heater above your head, while LEDs feel milder even though the total heat in the room evens out.
3. Practical impact on grow rooms
HPS tends to spike room temps faster because of intense radiant heat and hotter bulb temps (can reach 1000–2000°F).
LED heat is more diffuse,
coming mainly from driver/electronics and absorbed light rather than a scorching bulb, so cooling systems work more efficiently.
So:
Short term: LEDs seem cooler, easier to manage.
Long term, closed system: 600W in still means 600W worth of heat load eventually.
Me:
I think the og question was; "can led heat be contained and exhausted to outside of a room or tent", I say yes, but with the same caveat as hps. Hot components would have to be placed in a sealed, (preferably) insulated system that pulls air from a source other than the tent or room, then runs it over the hot components, and exhausts it outside of the tent or room. The component(s) would stay hot, but the radiant and convective heat generated would be reduced to the intake source heat.
In my last big grow, I was pulling cool air from a crawl space under the house (thru a plenum with hvac filters), thru sealed lights (hps/grow wings) and exhausted into the attic. The light hoods then stayed just a couple degrees warmer than the crawl space air temp.
Nobody can tell me that properly used (sealed) tubes and hoods don't remove a significant amount of heat from a grow space while allowing the plants to grow right to the lights without (physical heat) burning them; however they can still be bleached in some circumstances by high intensity light
