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Does a Light Bulb Make a Room Hotter?

Yes, a light bulb makes a room hotter, even though marginally. This is because it converts electric energy into light or heat (thermal) energy. How the light bulb operates determines how much light and heat it produces. For example, the filament in an incandescent light bulb produces a high amount of heat, making it hot. 

But what is the relationship between light bulbs and room temperature? When they produce light, bulbs lose a small amount of heat to the atmosphere. This heat can lead to marginal changes in a room’s temperature. However, the increase in room temperature could be minimal, considering the room size. 

When the American government announced the incandescent lightbulb ban in 2022, some people suggested that this was because such light bulbs had a high heat output and therefore wasted energy. This opened up the debate around light bulbs and the production of heat. Could the high heat output of incandescent bulbs be to blame for the ban?  

In this post, I explain which light bulbs, if any, produce heat, how much heat they emit, and what a heat bulb is. I offer some advice on picking the best light bulbs. 

Can a Light Bulb Cause Heat?

Light bulbs can cause heat. All light bulbs convert electrical energy into light and heat (thermal) energy. However, various bulbs produce variable heat and light depending on their wattages. 

Although a light bulb’s primary function is to emit light, some bulbs also produce heat due to inefficient energy conversion. But you can choose a heat bulb if you want more heat than light.

Light bulbs come in three main varieties:

Fluorescent Light Bulbs

The bulb comprises a glass tube coated with white powder (phosphor) on the inside. A ballast produces a high current that flows through the light bulb. When the current combines with the gas inside, it creates ultraviolet energy, which heats the phosphor converting it into light. The fluorescent light bulb generates very little heat energy since no resistance exists.

 A fluorescent light’s surface can get as hot as 100 °F (37.78 °C). However, fluorescent lights give off significantly less heat than standard incandescent bulbs. 

Incandescent Light Bulbs

The incandescent light bulb comprises a glass shell surrounding a metal wire filament made from tungsten. An electric current heats the filament until it produces light. The filament wire of a 75-watt incandescent bulb reaches a temperature of roughly 4500°F (2482°C)! The electrical contacts in incandescent light bulbs typically pass through a stem or glass mount attached to the bulb’s base. 

The glass enclosure contains either inert gas or a vacuum, which preserves and protects the filament from evaporating.  Sadly, much energy gets lost during the production of light. As a result, incandescent light bulbs emit both light and heat energy. The temperature increases as the light bulb’s wattage increases. 

To provide the same quantity of light, a standard incandescent light bulb requires around four times the energy of a fluorescent bulb.

High-Intensity Discharge light bulbs

High-Intensity Discharge (HID) light bulbs create an electric arc between two electrodes after passing through ionized gas. The two materials that produce the electric arc are quartz and sintered alumina. An outer glass protects the HID light bulb’s core part, which keeps more heat inside. The HID light bulbs produce a lot of heat, but most of it falls within the IR and UV radiation spectra

The arc emits visible light naturally without the requirement for coating, unlike fluorescent light bulbs that include phosphor that lights when UV light reaches it.

However, the two have one thing in common—they require a ballast. The ballast in HID light bulbs regulates the current flow so that the bulb can maintain an arc between its two electrodes. 

HID light bulbs are the best choice when high intensity, high efficiency, or extensive area lighting is necessary. Outdoor applications, such as stadium lighting, gymnasium, warehouse, or large public places, often require HID light bulbs.

How Much Heat Does a Light Bulb Give Off?

Light bulbs come in various shapes, sizes, wattages, and voltages. Bulbs with higher wattages emit more heat. This is why you should avoid touching high-wattage (incandescent light bulbs) to avoid getting burnt.  

The table below from the LED lighting supplier Ledsmaster shows the temperatures that light bulbs heat up to (comparing incandescent and LED).

WattageIncandescentLED
1550°F12.5°F
2570°F17.5°F
40115°F29°F
60200°F50°F
150250°F63°F

What Is the Difference Between a Light Bulb and a Heat Bulb?

A heat bulb is simply an incandescent bulb that primarily generates heat by emitting more infrared radiation. Therefore, the heat bulb is more effective as a source of warmth than a standard light bulb due to the increased radiant heat. 

Heat bulbs differ from light bulbs in several ways: 

  • While ordinary incandescent bulbs cannot operate at more than 100w, heat bulbs can operate at 2kW. 
  • Heat bulbs get preference for their warming capabilities over their illumination capabilities. Filters or reflectors assist the heat bulbs in condensing heat radiation. 
  • Heat bulbs are incandescent bulbs that operate with stronger currents, increasing temperatures. 
  • Compared to heat bulbs, incandescent light bulbs comprise less durable components. Because of the large currents, the heat bulb’s stronger components prevent blowout. 

Heat bulbs are the best choice for applications where heat generation is crucial. These applications include bathrooms, when drying chemicals and paint, animal enclosures, and kitchens. However, because they function at temperatures far greater than regular light bulbs, you should only use them when there is no fire risk. 

Do LED Lights Get Hot? 

Light Emitting Diode (LED) light bulbs get hot, but not as hot as fluorescent, incandescent, and High-Intensity Discharge light bulbs. Heat escapes from the light source via the LED bulb’s base, which also serves as a heat sink. However, if the heat bulb lacks adequate ventilation, it generates additional heat. LED lights, however, don’t generate enough heat to start a fire unless the wiring circuit is faulty. 

A diode is an electrical component with two electrodes—the cathode and the anode. Starting at the anode and finishing at the cathode, electrical current travels through the diode in a single direction. Semiconductors, such as silicon or selenium, create diodes. Semiconductors are notoriously bad at transferring heat.    

Compared to incandescent bulbs, LED lights are 75% more energy efficient and significantly cooler. A circuit board that connects to several LED chips lights them up. Temperatures of the LED lights range from 140-212 degrees Fahrenheit. Thankfully, LED lights use more energy for light and less for heat. 

At the bottom of the bulb, the heat sink absorbs and distributes excessive energy.                                   Therefore, LED light bulbs require cool environments. Vents are necessary for LED bulbs to allow ventilation and heat distribution. 

How to Choose the Best Light Bulbs

There has been a significant change in the lighting industry over the last few years. The incandescent light bulb, which consumes much energy, is now making way for more efficient compact fluorescent light bulbs and LEDs. But how do you choose the best light bulb among all these varieties?

Here are a few insights that can help you choose the best light bulbs: 

Energy Use

While slightly more expensive than incandescent light bulbs, LEDs have a 25 times longer lifespan. Additionally, LED lamps use 75% less energy, which makes them more cost-effective. 

Therefore, use models that have the Energy Star label. The label includes information about the color, brightness (in lumens), estimated annual cost, energy usage, and lifespan (which facilitates bulb comparison). 

Bulb Shape And Size

Check your existing bulb’s shape and base size before buying. The base is 26mm wide, and the bulb has an Edison screw if you notice an E26 base. If the shape is A21, the letter A indicates the bulb shape is arbitrary, which is the standard shape for incandescent bulbs.

The replacement lighting supplier, Bulbs.com, has created a useful shapes and sizes chart.  

Wattage

Most people think a bulb’s wattage tells you how bright it is. Wrong! Instead, the bulb’s wattage shows how much energy it uses. If you need help calculating the right LED wattage, divide your typical incandescent wattage by five. Consider switching to a 12-watt LED light, for instance, if you typically use a 60-watt incandescent bulb.

Your home’s fixtures are rated for the maximum energy they can handle safely.  Lumens, however, are a more accurate way to quantify light production. Choose the one with the highest lumen if you want a brighter light bulb. Therefore, choose the 800-lumen bulb if you often purchase 60-watt bulbs. 

Light Colors

Did you know that the light color of your bulb can influence the mood in the room? Using soft white or warm white light color bulbs creates a cozy, pleasant atmosphere. Choose cool and brilliant white light color bulbs for a lively but not harsh ambiance. Because daylight color bulbs show off everything clearly, it is said to be the color of productivity. 

 The Kelvin temperature scale measures light color or appearance. 

The table below from the American retail company specializing in home improvement, Lowes, presents various light colors, ranges, and recommended uses.

ColorRange( Kelvin)Ideal usage
Soft whiteYellow range ( 2700-3000)The best color for lighting bedrooms, living rooms, and dens and the standard color of incandescent bulbs.
Warm whiteBetween yellow and white ranges (3000-4000)Perfect for bathrooms, workspaces, and kitchens.
Bright whiteBetween white and blue ranges (4000-5000)Ideal for kitchens and bathrooms with white or chrome fixtures.
DaylightBlue range (5000-6500)The best for reading because they are bright but are non-strenuous on the eyes.

Smart technology

Now that “smart bulbs” are readily accessible, you can select a light bulb based on your requirements. For instance, you can dim the lights using your phone’s settings, Alexa, Siri, or Google Assistant, if your children have trouble falling asleep with the lights off. 

Therefore, check the label to ensure your chosen light bulb can dim. 

Conclusion

The wattage of a light bulb influences how much energy becomes heat or light in a space. Only 10% of an incandescent light bulb’s energy converts to light. The remaining 90% goes to waste as heat. As a result of the heat escaping into the surroundings, the room becomes marginally warmer. 

LEDs and HIDS convert their energy more efficiently. For instance, compared to incandescent and fluorescent light bulbs, LEDs consume 75% less energy. You can use a heat bulb if there is a greater need for heat. 

When selecting the best one, consider the bulb’s size, shape, wattage, energy star label, and color.

FAQs

Does a light bulb generate heat in a room?

Yes, a light bulb generates heat in a room. However, the amount of heat it generates depends on the bulb type and the room size. Various light bulbs emit different levels of heat. Fluorescent light bulbs emit about 25% of the heat that an incandescent light bulb emits.

Most people use incandescent light bulbs to keep their rooms warm. However, this will only work if the room is small.

Can a light bulb contribute to the overall temperature increase in a room?

Yes, some light bulbs raise the overall temperature of a room. Small spaces with inadequate ventilation will experience an increase in temperature from the light bulb more than large spaces. Light bulbs generate heat which transfers to the surroundings. 

Incandescent lights with a higher wattage generate more heat. Consequently, a room with high-wattage light bulbs will experience a higher temperature rise. 

Author

  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

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