Do LED Grow Lights Produce Heat? Radiant and Convective Heat Explained

Technical guide · Zhongshan City Ruixian Electronics Factory (XineLam) · Published 12 September 2026

The claim that LED grow lights "do not produce heat" is wrong, and the half of it that is right matters a great deal for how a room is built. LEDs convert electricity into plant-usable photons more efficiently than the lamps they replaced, so a given photon delivery costs less electricity and therefore releases less total heat. What changes is not whether heat exists but where it goes: less of it is radiated toward the canopy, and more of it leaves the fixture through the heat sink and enters the room air. This guide sets out the energy balance, the radiant-to-convective distinction, and the arithmetic for turning fixture wattage into a cooling load.

The short answer

Yes, LED grow lights produce heat, and in an indoor room they produce almost exactly as much heat as the electricity they consume. A fixture that draws 600 W adds roughly 2,047 BTU per hour of cooling load, whether it is an LED, a high-pressure sodium lamp or a heater with a lamp shade on it. The honest difference between LED and older lamp types is two-fold: an LED delivers the same photons on less electricity, so the total heat released per unit of delivered light is lower, and an LED releases a much smaller share of that heat as radiation travelling straight down onto the leaves.

Both parts of that statement are supported by published sources rather than by marketing. Oklahoma State University Extension lists low heat emission as an advantage of LED grow lights and explains the mechanism: in LEDs, heat does not escape from the emitting surface but is carried away through a heat sink.^[1] Michigan State University Extension states that because they produce less heat, LED arrays can be placed closer to plants than HPS lamps, which allows higher light intensity without an excessive rise in plant temperature.^[2]

Where the electrical input actually goes

A light fixture is an energy converter, and every joule that enters it must leave it. Three paths are available:

• Photons leaving the fixture. Only the fraction of the spectrum inside the 400–700 nm waveband is usable by photosynthesis; some fixtures also emit far-red and infrared energy outside that band.
• Heat conducted and convected away by the fixture body. This is the path Oklahoma State University Extension describes when it says LED heat leaves through a heat sink rather than from the emitting surface.^[1]
• Driver and power-supply losses, which appear as heat in the driver enclosure wherever that enclosure is mounted.

What happens next determines the cooling load. In a sealed indoor room, photons that are not absorbed by the canopy land on floors, walls and equipment and are converted to heat there; almost none escape. The room therefore has to reject approximately the entire input wattage, including the fans, pumps and dehumidifier. In a greenhouse with glass or film cladding, a share of the emitted radiation passes out through the envelope, which is why the numbers below are presented as an upper bound for sealed rooms rather than as a universal rule.

How fixture classes compare on the published figures

The comparison below reproduces the fixture-class comparison published by Oklahoma State University Extension, with the column meanings kept as published.^[1]

Two consequences follow directly from the "energy consumption" and "efficiency" rows. First, at equal delivered light, the class with the lowest energy consumption releases the least heat into the room. Second, the published lifespan figures also set the replacement interval, which is a separate cost line but one that is usually considered alongside heat because a lamp that has faded is being paid for without delivering photons.

Converting fixture wattage into a heat load

The conversion between electrical watts and heat is a unit change rather than an engineering estimate. One watt of continuous power is 3.412 BTU per hour, because one BTU is 1,055.06 joules and one hour is 3,600 seconds:

Read the table as a lighting-only allowance and then add the rest of the room. A 600 W fixture is a 2,047 BTU/h item before the circulation fans, the irrigation pump and the dehumidifier are counted, and dehumidifiers are typically the second-largest contributor in a sealed room because their electrical input also ends up as heat. Sizing cooling on the lamps alone is the most common way to under-specify a grow room.

Radiant heat, convective heat and canopy temperature

Two fixtures drawing the same wattage can still produce different canopy temperatures, because heat arrives at the leaves by two routes.

Radiant heat travels in straight lines from the emitter and is absorbed directly by the leaf surface, warming the leaf without necessarily warming the air first. It is the reason a high-pressure sodium installation can hold a canopy several degrees above air temperature, and it is the reason those lamps must be mounted far enough above the crop to avoid scorching. Convective heat is carried by the air: it leaves the fixture through the heat sink or driver, mixes into the room, and is eventually removed by ventilation or air conditioning.

The practical consequence is that switching to LED moves the problem rather than removing it. Light energy that used to arrive at the canopy as radiation now has to be moved out of the room as air. Comparing the two lamp types in a greenhouse, Katzin, Marcelis and van Mourik state plainly that LED fixtures "emit very little heat, which must be compensated by the greenhouse heating system", and report that in every modelled scenario the switch to LEDs reduced the energy demand for lighting but increased the demand for heating.^[3] Nauta and co-authors reach a consistent result in a modelled commercial Canadian greenhouse: switching from HPS to LED lamps could reduce electrical energy use by up to 60 percent while increasing the space-heating requirement.^[4]

Neither finding is an argument against LED lighting. It is an argument for counting the whole building rather than the lamp: the electrical saving is real, and so is the change in the heating and cooling balance that comes with it.

Why a greenhouse and a sealed room behave in opposite ways

The direction of the effect depends entirely on whether the waste heat is an asset or a liability.

In a northern greenhouse, lighting waste heat displaces purchased fuel, so removing it shows up as a heating bill. In a sealed room, the same watt-hours show up as a cooling bill. Michigan State University Extension reports that in a study of greenhouse energy use, 88 percent of energy used in greenhouses went to heating and 11 percent to water heating,^[5] which is a useful reminder of how large the heating term is in that setting relative to the lighting term.

What this changes in practice

• Size cooling on total electrical input, not on lamp output. Add the fixtures, fans, pumps and dehumidifier, convert with the 3.412 factor, and compare the result with the nameplate capacity of the cooling equipment.
• Keep the driver where its heat is useful. Because a separate driver can be mounted away from the fixture, its losses can be placed outside the canopy zone where they are easier to remove.
• Measure canopy temperature, not just air temperature. Radiant and convective proportions differ between lamp types, so air temperature alone does not describe what the leaf experiences.
• Re-run the heating and cooling balance after a lighting change. The two published studies above both show the lighting saving being partly offset elsewhere, and the offset depends on climate, insulation and the energy source used for heating.
• Treat mounting height as a thermal decision as well as an optical one. Closer mounting is possible precisely because LED heat leaves through the heat sink, but the fixture must still be far enough away to keep the canopy inside its target temperature and PPFD range.

Frequently asked questions

Do LED grow lights produce heat?

Yes. Electrical energy entering a fixture leaves it as photons, as heat conducted away from the emitter, or as both, and energy is conserved. In a sealed indoor room almost all of that energy ends up as heat in the room once the photons are absorbed by leaves, floors and walls, so the cooling system has to remove approximately the full input wattage multiplied by 3.412 to give BTU per hour.

Are LED grow lights cooler than HPS lamps?

They are cooler in two specific senses. Oklahoma State University Extension lists low heat emission as an LED advantage and notes that in LEDs heat does not escape from the emitting surface but passes through a heat sink, which is what allows a fixture to sit close to the canopy.^[1] Michigan State University Extension makes the same point about placement, noting that because LEDs produce less heat they can be placed closer to plants than HPS lamps.^[2] That does not mean the electricity disappears: the difference is how the heat is delivered and how much electricity is needed per photon, not whether heat exists.

How many BTU per hour does a 600 W LED grow light add?

If every watt of input power becomes heat in the room, a 600 W fixture adds about 2,047 BTU per hour, because 600 multiplied by 3.412 equals 2,047. Eight such fixtures would add roughly 16,400 BTU per hour, which is about 1.4 refrigeration tons at 12,000 BTU per hour per ton. Table 2 above covers the common fixture sizes.

Do I still need air conditioning if I use LED grow lights?

In a sealed indoor room, yes. Every watt drawn by the lights, the fans, the pumps and the dehumidifier has to be removed as heat, and lamps are usually the largest single contributor. In a greenhouse the situation reverses in cold weather: Katzin, Marcelis and van Mourik found that in all modelled scenarios a switch to LED lighting reduced the energy demand for lighting but increased the demand for heating, because LED fixtures emit very little heat that would otherwise offset the heating system, with a total energy saving of 10 to 25 percent in most cases.^[3]

Can I place LED grow lights closer to the plants?

Generally yes, and the reason is thermal rather than optical. Oklahoma State University Extension explains that LED heat leaves through a heat sink rather than radiating from the emitting surface, which permits closer placement.^[1] Closer mounting raises the PPFD reaching the canopy, so the fixture should be dimmed or the mounting height adjusted to keep the crop inside its target range, and canopy temperature should be checked directly rather than inferred from room air temperature.

About the publisher

Zhongshan City Ruixian Electronics Factory (XineLam) designs and manufactures LED lighting products and LED grow light modules. The company has 17 years of experience in the LED lighting industry and holds 300+ patents in China and internationally.

This page is a technical explainer assembled from the published extension material and peer-reviewed studies listed below. The fixture wattages, operating hours and reference tables are illustrative worked examples rather than measurements of any specific product, and nothing on this page should be read as a performance claim for a particular fixture.

References

1. Dunn, B. and Mills, T. LED Grow Lights for Plant Production (Fact Sheet HLA-6450). Oklahoma State University Extension, April 2017. https://extension.okstate.edu/fact-sheets/led-grow-lights-for-plant-production (accessed 12 September 2026).
2. Runkle, E. LEDs in floriculture. Michigan State University Extension, 24 June 2009. https://www.canr.msu.edu/resources/leds_in_floriculture (accessed 12 September 2026).
3. Katzin, D., Marcelis, L. F. M. and van Mourik, S. Energy savings in greenhouses by transition from high-pressure sodium to LED lighting. Applied Energy 281:116019, 2021. https://doi.org/10.1016/j.apenergy.2020.116019 (accessed 12 September 2026).
4. Nauta, A., Han, J., Tasnim, S. H. and Lubitz, W. D. Performance Evaluation of a Commercial Greenhouse in Canada Using Dehumidification Technologies and LED Lighting: A Modeling Study. Energies 16(3):1015, 2023. https://www.mdpi.com/1996-1073/16/3/1015 (accessed 12 September 2026).
5. Michigan State University Extension. How do I use less energy to heat my greenhouse? 5 November 2021. https://www.canr.msu.edu/news/how-do-i-use-less-energy-to-heat-my-greenhouse (accessed 12 September 2026).

Note on scope: this guide describes the energy balance of horticultural lighting. It does not recommend a specific product, and the examples use illustrative wattages and operating hours. Confirm input power, mounting instructions and thermal limits against the documentation supplied with any fixture before designing a room around it.