Founder | BPI® Energy Auditor Certified Professional

When choosing what type of light bulbs to get for your home, you should consider several different factors. One of the most critical parameters is the heat produced by a bulb at any time. The heat is significant because it indicates how much energy is being used and may affect the room’s temperature.

So let’s see how different bulbs compare for the same wattage to help you decide which is best for your home. In the rest of the article, we will also answer some additional questions you might have regarding the heat produced by different kinds of light bulbs.

Table of Contents

Which Light Bulbs Produce the Most Heat?

Incandescent bulbs produce the most heat, using only 2-5% of the energy they receive for lighting. Halogen and CFL bulbs also generate quite a lot of heat – 90 and 80 percent of their power, respectively. LED is the most efficient bulb type nowadays, losing only 60% of its energy in heat.

Now that you’ve gotten an overview let’s look at the specifics of heat output.

The Heat Output of Popular Bulbs

The purpose of light bulbs is to convert electrical energy into light, and they can do so at different levels of efficiency. But, as the second law of thermodynamics dictates, some energy will “go to waste” or turn into heat during the transfer, regardless of the bulb type.

Some types of light bulbs are so inefficient that only a tiny percentage of the electric energy that goes into them turns into light. So, naturally, these are the bulbs that cost you more in energy bills. Other bulbs are better at transforming electricity, which allows them to convert a significant part into light, emitting less heat.

Let’s see the four main types of bulbs and how much heat they can produce:

Type	Percentage of energy lost as heat
Incandescent bulbs	95%
Halogen bulbs	90%
CFL bulbs	80%
LED bulbs	50-60%

Incandescent Bulbs

Incandescent light bulbs produce the most heat and are consequently the least efficient. Their design is more than a century old—it requires electricity to pass through a metal filament that gets incredibly hot and emits light.

A glowing A19 light bulb hanging from a fixture trasnsposed against a dark background

As a result, around 95% of the electricity that goes into an incandescent light bulb turns into heat. This ratio is a pretty good indicator of the efficiency of these light bulbs.

While they are relatively cheap, they can cost you quite a lot in energy bills. Filament bulbs are incredibly hot; they can reach up to 4,600 degrees Farenheit (2,538 ºC), so you shouldn’t attempt to touch them when they’re on.

Halogen Bulbs

Halogen bulbs are similar to incandescent lights but are slightly more advanced. Just like filament bulbs, they require electricity to pass through a tungsten filament, which heats up. The upgrade from its predecessors comes in the form of a capsule around the filament, filled with halogen gas made of iodine and bromine.

a closeup of a halogen bulb with a blue background

Since the principle is more or less the same as incandescent bulbs, halogen bulbs also waste a lot of energy in the form of heat. A typical halogen bulb can be expected only to use 10% of the energy it receives for lighting. The other 90% turns into heat.

As you can imagine, these light bulbs are very hot to the touch and can affect the temperature of the environment around them.

CFL Bulbs

The compact fluorescent lamp (CFL) bulb represents a significant advancement in light bulb technology. Unlike the two previous types, CFL bulbs no longer have a metal filament inside.

Instead, they have a spiral tube filled with mercury and argon. When electricity passes through it, the gas molecules start moving, producing light.

a bunch of CFL light bulbs on a table with a black background

However, although the technology is much more different, heat loss is still considerable. A CFL bulb loses 80% of the electric energy into heat. Although it’s a significant improvement from the predecessors, it’s still relatively inefficient. As a result, CFL bulbs get very hot, reaching 179.2 degrees Fahrenheit (82 ºC).

LED Bulbs

If CFL bulbs represented a turn in light bulb technology, LED lights could be considered a revolution. LED bulbs contain no filaments or gas-filled tubes. Instead, they use light-emitting diodes (LED), semiconductors that light up when an electric current passes through them.

LED bulbs are now the most efficient, converting around 40% of their energy into light, while the rest is lost as heat. While this 60% heat loss may seem inefficient, it’s still a significant improvement from the previous iterations.

LED lights are not hot to the touch, so you may safely handle them while they are on. Nowadays, LED lighting is the best option for efficient and eco-friendly homes.

Do Energy-Saving Bulbs Get Hot?

Most energy-saving bulbs nowadays are LED, but you can also find CFL options. They are considered efficient because they use a lot of energy for lighting and produce less heat. LED lights don’t get hot since they are more efficient; CFL bulbs may reach higher temperatures.

Even though LED bulbs don’t get hot, it doesn’t mean they produce no heat. As you read above, only 40% of the electricity going into these bulbs is used for lighting. However, the heat produced is low enough to make them significantly less hot than alternatives.

Various types of LED light bulbs transposed above a white background — LED bulbs come in various shapes and sizes.

Factors Affecting the Amount of Heat

Besides the technology used for a light bulb, are there any variables that can truncate the heat emitted by a bulb?

Plenty of parameters can affect how hot a light bulb can get. Of course, the voltage and size can make a significant difference, but the external environment can have a significant effect too.

Let’s consider these variables in detail.

Bulb Wattage

The wattage indicates the amount of power your light bulb can handle. The more energy it can handle, the hotter it can get since, as you saw, most electricity going into all bulb varieties turns into heat.

Wattage is very important. You should note it because using bulbs with the wrong wattage can cause problems. If you use bulbs with a higher wattage than your fixture can handle, the bulb will become hotter than the fixture can handle, damaging it permanently.

Bulb Age

As bulbs age, they become more defective and less efficient because parts of them deteriorate. As a result, they release more heat and use less energy for lighting, attenuating their efficiency. This explains why older bulbs can get very hot very fast.

It should be emphasized that age issues affect older types of bulbs more than LED bulbs. LED lights are designed to last for more than a decade with no problem; even older LED bulbs won’t give off as much heat as new incandescent bulbs.

Bulb Size

The size of the bulb makes a significant difference. Larger bulbs inherently have a higher wattage, which, as you just read, will contribute to the bulb emitting more heat.

LED lights in a row of increasingly smaller sizes

The larger surface area of more substantial bulbs allows them to release more heat quickly, which is why you may notice that bigger bulbs get hot faster. Once again, this reasoning applies more to filament and fluorescent CFL lights than LED lights.

Does Color Make a Difference?

You may wonder if bulbs that emit white light may be slightly less hot than those that emit yellow light. As the latter is a warmer color, one may think it might require more energy, translating into more heat produced. The warmer color may give the impression that the room is hotter.

However, the color of the light does not make a difference in the heat produced by a light bulb. Whatever color you choose, you should keep in mind that there are other factors affecting the amount of heat, which I have mentioned above.

However, the color of the light can trick the brain into believing that there are slight temperature changes, so choose whichever color makes you feel better.

Final Thoughts

As you can see, different types of light bulbs produce varying levels of heat, but it’s safe to say that the newer the technology of the bulb is, the less heat it releases. So understandably, more recent models like LED bulbs are also more efficient.

Besides the bulb technology, the wattage, age, and size also influences the heat produced.

It’s Hot in Here: Which Light Bulbs Produce the Most Heat