How much HVAC do I need to cool LED Lights? We hear this question all the time, especially in the summer. Or when planning a grow room.Our rule of thumb – it takes one watt of air conditioning to cool three watts of lighting.When you turn on a light some of the energy is turned into photons and some of the energy is turned into heat. In the case of LEDs, about 40% of the energy is turned into light and 60% is turned into heat.Unfortunately…. you need to cool all of the energy, even the energy emitted as light. This is because the emitted photons will end up heating up the surfaces they hit. The heat/light ratio does impact your HVAC design but a good estimate is that you need to cool every watt of lighting.