Do LEDs really produce heat?

Susan Fernandez January 01 2022

Can LED light be hot?

They don't produce heat like an incandescent bulb, but that doesn't mean they're not producing heat. Let's look at what LED lights are and how they work to see if LEDs can produce heat.

LED stands for light-emitting diodes. It is a semiconductor device used for visual signaling and illumination. They were first used for this purpose in 1959, after experiments with radio tubes led by Nick Holonyak Jr., who was later known as the "father" of the light-emitting diode (LED). There are many different kinds of LEDs. Red ones emit light at about 600-700 nanometers (nm), yellow/green ones at around 590 nm, and blue/violet ones at 400-450 nm.

The human eye cannot distinguish between different colors of light that are close together on the visible spectrum, so to our eyes all LEDs that are not red look the same. This is why white LEDs are created by combining several different colored LEDs in very specific ratios. The light from each color LED is mixed before it enters your eyeball.

What happens when electricity runs through a diode?

When you hook up a battery or power source to a diode, electrons flow across the junction connecting two semiconductors. When there is only one semiconductor, this process is called forward bias. When there are two doped semi-conductors connected to an external power source, this process is called reverse bias. There's no current without a forward or reverse bias.

However, backward isn't what happens when you hook up a battery to an LED. Electrons are trying to flow across the junction in one direction, but they're being blocked by other electrons in semiconductors on the other side of the junction. As more and more electrons stack up at the junction, their kinetic energy increases.

They don't have anything to bounce off of, so this makes them speed up even more. This stacking-up effect is called impact ionization. When enough electrons pile up at the junction, there's finally enough energy for some electrons to jump right over that missing piece of semiconductor (called a recombination event). It takes about 1 volt for this electron avalanche to happen, which is why LEDs are usually hooked up to batteries with at least 1.5 volts.

So, what about all that wasted energy?

When an electron drops from a higher level to a lower one it releases the difference in energy as light. This is called fluorescence. Most of the time this light is not visible to humans because its wavelength is outside of our range of sensitivity (between 390-700 nm).

However, you can see this process happening if you use blue LEDS and color filters. The filters block out other colors while letting only blue through, so bluish-white LEDs appear when they're hooked up to power sources -- but they aren't actually white. You can also hook them up backward so that they emit ultraviolet light, which triggers fluorescence in certain materials. When blue LEDS are hooked up backward, they emit bluish-white light and are used to cure epoxy resins.

How do LEDs heat up?

LEDs heat up while they're on because electrons are still impacting the semiconductor junction even after the electron avalanche has occurred. This is why turning lights off when you're not using them will save energy.

However, this heating effect only applies to high power consumption LEDs, particularly ones that require more than 1 watt of power (most households LED light bulbs to consume about 10 watts). High power LEDs become hot because of their large voltage drop -- if you hook a 100 W incandescent bulb to a 120 V socket it will also get very hot. High-power LEDs are built with special heat-sinks to dissipate the excess heat so that they don't fail early.

LED heat and incandescent heat

These 2 types of heat are different because incandescent heat is caused by the air around a hot filament becoming "white-hot" and LED heat is from photons bouncing around inside a semiconductor junction. So, while you can feel the heat coming off an incandescent light bulb you cannot feel the heat coming off an LED.

That is why it is better to use LED bulbs instead of regular ones because LEDs do not heat up as much as regular lights and they are energy efficient. At the same time, incandescent bulbs are used for decorative purposes.

So, while LEDs are used in flashlights and normal lights, incandescent bulbs are used where the light is required only for decorative purposes.

What light type produces the most and the least range of heat?

All types of bulbs have their own pros and cons. Although LED bulbs produce less range of heat, they are much more energy-efficient than other bulb types like CFL and incandescent lights. But LED lights also take a lot longer to warm up because the heating process for LEDs comes from within.

Thus, the least heat is usually produced by LEDs (about 20-50%), then go fluorescent bulbs (40%), then you will meet halogen bulbs with 80% and finally, the most heat is produced by incandescent bulbs (85%). Though, fluorescent tubes produce about 20% of heat and may be considered as the best option if you are looking for one with the least heat production.

But in such a case, why don`t people prefer fluorescent bulbs? That is all because of their poor quality, low light production, and long warm-up times.

Though, LED bulbs produce less heat they do not last as long as the incandescent ones because of the healing process which is within the LED. Thus, they have a limited lifetime in comparison with incandescent lights that produce most heat but also last a very long time.

But at the same time, LEDs are energy efficient and save more power than other types of lights. So if you have an option to replace your old bulb with LEDs we would highly recommend you do so!

A common myth about lighting is that fluorescent lamps generate more heat than 'normal' lamps when switched on due to being less efficient. In fact, fluorescent lamps do generate more heat when initially turned on because a high voltage needs to be applied across the lamp in order to 'ignite' it.

Using less energy means that any lights using LEDs will also produce the least amount of heat over time. As seen from the post's tags, all types of lighting systems have their own pros and cons.

While incandescent lamps are very good at generating light, they produce a large amount of waste heat requiring bulky cooling systems which makes them one of the most inefficient forms of electricity conversion available. Incandescent lamps also have a very short lifespan being subject to failure after only a few hours of use due to filament evaporation. This reduces their overall cost-effectiveness as well as environmental benefits.

LEDs are highly efficient but have a much higher initial cost due to their complex design. The LED has two terminals, one that emits electrons (negative) and another that accepts them (positive). Current flows into the negative end until it reaches a 'band gap' voltage where electron movement is restricted by the lack of sufficient energy to overcome the bandgap.

This triggers an electron avalanche within the semiconductor material producing an abundance of free electrons which flow through the junction until they reach the positive terminal where they are passed on to other active LEDs in series creating a chain reaction that spreads rapidly across multiple LEDs once initiated. These electrons produce photons as they pass through the 'active area' of the LED at speeds approaching 1/10th the speed of light.

Incandescent lamps are still widely used where the light is required only for decorative purposes as they are inexpensive to purchase, simple to install, and provide a relatively accurate color rendering index which makes them ideal for some areas of lighting such as household or low-end office lighting.

However, their energy efficiency leaves much to be desired as one of the least energy-efficient forms of electrical conversion available with an efficacy between 5-13 lumens per watt compared to around 50+ lumens per watt for standard fluorescent lamps. They also have a very short life span being subject to failure after just a few hours of use due to filament evaporation. This reduces their overall cost-effectiveness as well as environmental benefits.

How long do LEDs last?

LEDs have a relatively long life span, some as high as 50,000 hours (~20 years). However, this is reduced by the fact that they fall asleep and lose brightness over time. LEDs come with a driving current that must be supplied at all times to maintain brightness levels and prevent failure.

If this current drops too low then the LED will go to sleep and its brightness will start to fade along with any color shift on some models. It`s worth noting that older drivers don't usually fail on their own but do become more inefficient over time thus slightly increasing operating costs so it may be wise not to leave them running for extended periods of time unattended.

Fluorescent lamps have an average lifespan between 6-18 months although there is a lot of variation depending on the actual lamp and manufacturer. Also, fluorescent lamps operate at very high temperatures which limits their average lifespan to around 6000 hours before filament evaporation causes failure.

Their short life span can be attributed to the nature of Fluorescent lighting as the cracking and subsequent vaporization of Tungsten electrodes is necessary for it to work due to gas atoms inside the tube being excited by heat which releases UV light when they return to their normal state. This process, while effective in producing light also has a negative effect on lamp life compared with incandescent lamps where the filament emits visible light only after breaking down into Tungsten + Oxygen during operation due to inert gases preventing oxidation.

Fluorescent lamps are commonly used in a wide array of applications from industrial equipment with long life requirements to household lighting due to their high efficiency and low power consumption. Although they have a longer life span than most incandescent lamps, the cost of replacing them regularly is still significant in the long term, especially when compared with LED lamps which require no replacement parts or gases.

What is the difference in light output for different bulbs?

The color temperature of a light source is a measure of its hue, or shade of white and can be defined as the temperature of an ideal black body emitting the same spectrum as the light being observed. It`s worth noting that fluorescent lamps have been developed to produce more colors than just white which makes them more versatile for certain applications such as commercial lighting where different color temperatures may be required.

However, most household users tend to favor whiter shades with stated color temperatures between 4000K-8000K on average which provides a wide range of applications from decoration to reading lights with high CRI ratings since it is one of the best representations of natural light.

LED lamps can emit a wide variety of colors depending on their internal components but the most common type used for household applications is the cool white LED which provides higher light output levels than warmer color temperatures with stated color temperatures between 5000K-6500K.


LEDs are actually more likely to produce heat through the conversion of electricity into light instead of being dissipated as heat. This makes them more efficient than most other types of lamps since they convert most of their input energy into output light which also reduces power supply requirements.

However, it is important to note that LEDs only produce visible light and no UV or Infrared radiation which means they can't be used for applications involving these ranges of the spectrum such as tanning beds, black lights, parabolic mirrors, etc.

Also LED life spans to vary depending on manufacturer, color temperature, and application but LEDs will always provide lower maintenance costs due to requiring no replacement parts over time compared with incandescent or fluorescent lighting options.