10 Minute Read

Ever wonder how incandescent lights and light emitting diodes (LEDs) compare? Well here’s a head-to-head comparison of the two followed by an in-depth discussion of each technology in turn.

Incandescent Lights

Incandescent Lighting Bulb

What is an Incandescent Light?

The incandescent light is your classic light bulb. It produces light by heating a wire filament to a temperature that results in the generation of light. The metal wire is surrounded by a translucent glass bulb that is either filled with an inert gas or evacuated (a vacuum).

What’s the Upside to Incandescent Lights?

They’re really cheap to manufacture and accordingly, they’re really cheap to purchase (typically a dollar or two). Incandescent bulbs are widely available and adaptable to a large range of voltages, light outputs, and current (working well with both AC and DC power). They are the cheapest light on the market.  

Additionally, incandescent lights have a notoriously g

ood ability to render color. The color rendering index (CRI) for an incandescent bulb with a color temperature of 2700K is 100 (a perfect score). As color temperature rises the CRI ratings drop off only slightly but typically remain above 95 (considered an excellent rating).

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What are the Major Deficiencies in Incandescent Lights?

Among the deficiencies in incandescent lighting are the following:

  1. Incandescent lights have the worst energy efficiency on the market. incandescent lamps have efficiency ratings around 10 lumens/watt. Unfortunately most of the energy they consume (~90%) goes into generating heat.
  2. Incandescent lights have the worst lifespan on the market. The average bulb lasts around 1,200 operating hours. This means that even though incandescent bulbs are cheap to purchase, you have to purchase a whole lot of them (50-100) to equal the lifespan of a single LED. Overall that means high maintenance costs.

Tell Us More About Your ProjectWhat are the Minor Deficiencies in Incandescent Lights?

Among the minor deficiencies in incandescent lighting are the following:

  1. Incandescent lights are omnidirectional. Omnidirectional lights produce light in 360 degrees. This is a large system inefficiency because at least half of the light needs to be reflected and redirected to the desired area being illuminated. The need for reflection and redirection of light means that the output is much less efficient for omnidirectional lights due to losses than it would be for the same light if it were directional by its nature.

Where are Incandescent Lights Commonly Used?

Common applications for incandescent lighting includes residential and interior lighting. It is typically not used in outdoor environments or for large organizations because of its short lifespan and poor energy efficiency.


What is a Light Emitting Diode (LED)?

LED stands for light emitting diode. A diode is an electrical device or component with two electrodes (an anode and a cathode) through which electricity flows - characteristically in only one direction (in through the anode and out through the cathode). Diodes are generally made from semi-conductive materials such as silicon or selenium - solid state substances that conduct electricity in some circumstances and not in others (e.g. at certain voltages, current levels, or light intensities). When current passes through the semiconductor material the device emits visible light. It is very much the opposite of a photovoltaic cell (a device that converts visible light into electrical current).

If you’re interested in the technical details of how an LED works you can read more about it here.

What’s the Major Upside to LED Lights?

There are four major advantages to LED lighting:

  1. LEDs have an extremely long lifespan relative to every other lighting technology (including LPS and fluorescent lights but especially compared to incandescent lights). New LEDs can last 50,000 to 100,000 hours or more. The typical lifespan for an incandescent bulb, by comparison, is 1-5% as long at best (roughly 1,200 hours).
  2. LEDs are extremely energy efficient relative to every other commercially available lighting technology. There are several reasons for this including the fact that they waste very little energy in the form of infrared radiation (heat), and they emit light directionally (over 180 degrees versus 360 degrees which means there are far fewer losses from the need to redirect or reflect light).
  3. Very high light quality
  4. Very low maintenance costs and hassle

What are Minor Upside to LED Lights?

In addition to the major advantages, LED lights also offer several smaller perks. These include the following:

  1. Accessories: LEDs require far fewer accessory lamp parts.
  2. Color: LEDs can be designed to generate the entire spectrum of visible light colors without having to use the traditional color filters required by traditional lighting solutions.
  3. Directional: LEDs are naturally directional (they emit light for 180 degrees by default).
  4. Size: LEDs can be much smaller than other lights (even incandescent).
  5. Warm-Up: LEDs have faster switching (no warm-up or cool-down period).

What’s the Downside to LED Lights?

Considering the upside you might think that LED lights are a no-brainer. While this is increasingly becoming the case, there are still a few tradeoffs that need to be made when you choose LED:  

In particular, LED lights are relatively expensive. The up-front costs of an LED lighting project are typically greater than most of the alternatives. This is by far the biggest downside that needs to be considered. That said, the price of LEDs are rapidly decreasing and as they continue to be adopted en masse the price will continue to drop.

If you've received a proposal for LED lights that's too expensive (or need a proposal) our value engineering service can help.

Where is LED Commonly Used?

The first practical use of LEDs was in circuit boards for computers. Since then they have gradually expanded their applications to include traffic lights, lighted signs, and more recently, indoor and outdoor lighting. LED lights are a wonderful solution for gymnasiums, warehouses, schools and commercial buildings. They are also adaptable for large public areas (which require powerful, efficient lights over a large area), road lighting (which offer significant color advantages over low and high pressure sodium lights), and parking lots. For an interesting take on the history of street lighting in the United States read here.

Further Qualitative Comparison

What’s the Difference Between Sodium Vapor and LED Lights?

The two different technologies are entirely different methods of producing light. Sodium vapor bulbs contain metals that are evaporated into inert gas within the glass casing while LEDs are a solid state technology. Both technologies are very efficient. The difference is that sodium vapor lights were the most efficient technology of the 1970s while LEDs are the modern day equivalent. Although sodium vapor lighting beats virtually every other technology in terms of energy efficiency (which is why it was chosen to illuminate the streets of so many cities), it loses out to LEDs. Both LEDs and sodium vapor lights emit electromagnetic radiation across a small portion of the visible light spectrum, however, LEDs waste much less energy producing waste heat and they also provide an incredibly better variety of high Color Rendering Index options to the user (thus eliminating the monochromatic black appearance of objects illuminated by LPS and HPS bulbs).

Why would LEDs put incandescent bulbs out of business?

Incandescent bulbs are very inefficient energy consumers. They convert less than 1/20th of the energy they consume into visible light. The vast majority (approximately 90%) is lost as heat.

This all translates to cost. Although the sticker price is low, incandescent bulbs will cost you money over time based on the inefficient way in which they operate and the frequency with which they must be replaced. In a large-scale building (like schoolshospitals, or commercial buildings), this inefficiency will really add up.

Read all lighting comparison posts!

Incandescent Lighting vs Light Emitting Diode (LED) Comparison

Correlated Color Temperature (read more here)

LEDs are available in a wide range of color temperatures that generally span from 2200K-6000K (ranging from “warm” yellow to light or “cool” blue).

Incandescent bulbs are also available in a range of color temperatures. The three primary options for consumers include Soft White (roughly 2700K – 3000K), Cool White (3500K – 4100K), and Daylight (5000K – 6500K).


CRI (read more here)

CRI for LED is highly dependent on the particular light in question. That said, a very broad spectrum of CRI values is available ranging generally from 65-95.

Incandescent bulbs generally have outstanding CRI ratings. A “warm” incandescent light (one with a color temperature of around 2700K) has a perfect CRI of 100. Values trend down a little as color temperature goes up but they tend to stay above 95 (still outstanding).

WINNER:  Incandescent

Cycling (Turning On/Off)

LEDs are an ideal light for purposely turning on and off because they respond rather instantaneously (there is no warm up or cool down period). They produce steady light without flicker.

Incandescent lights (similar to LED) do not generally flicker and/or cycle on and off as the bulb reaches the end of its useful life. Rather, incandescent light (again, like LEDs) tends to emit less light prior to total failure at the end of its useful life.

Incandescent lights also turn on rather instantaneously and produce steady light generally without flicker.



LEDs are very easy to dim and options are available to use anywhere from 100% of the light to 0.5%. LED dimming functions by either lowering the forward current or modulating the pulse duration. LED lights are not compatible with traditional incandescent dimmers (which lower the voltage sent to the light) so you need to purchase LED dimmer switches as well if you want to dim.

Incandescent lights are also very easy to dim. Incandescent light is extremely sensitive to voltage inputs and dimming works by exponentially emitting less light as the voltage is reduced. For better or worse (and different than LEDs) incandescent dimming has a larger effect on other characteristics of the light such as power consumption, lifetime, and color temperature.



LEDs emit light for 180 degrees. This is typically an advantage because light is usually desired over a target area (rather than all 360 degrees around the bulb). You can read more about the impact of directional lighting by learning about a measurement called “useful lumens” or “system efficiency.”

All Incandescent lights emit light omnidirectionally. This means they emit light 360 degrees, requiring fixture housings or reflectors to direct a large portion of the emissions to the desired target area or otherwise wasting the energy required to produce the light.



LEDs are very efficient relative to every lighting type on the market and extremely efficient relative to incandescent bulbs. Typical source efficiency ranges 37 and 120 lumens/watt. Where LEDs really shine, however, is in their system efficiency (the amount of light that actually reaches the target area after all losses are accounted for). Most values for LED system efficiency fall above 50 lumens/watt.

Incandescent lights are the worst of all the modern lights in terms of efficiency because so much of the energy (90%) goes towards generating heat instead of light. Their source efficiency (the amount of light emitted from the bulb in general) is around 10 lumens/watt and their system efficiency (the amount of light that actually reaches the target area after all losses are accounted for) is even lower.


Efficiency Droop

LED efficiency drops as current increases. Heat output also increases with additional current which decreases the lifetime of the device. The overall performance drop is relatively low over time with around 80% output being normal near the end of life. Recent advances by researchers who have identified the reasons for droop in LEDs look to reduce losses even further.

Although incandescent lifespan is extremely short (around 1,200 hours), the bulbs maintain their luminescence really well throughout.


Emissions (In the Visible Spectrum)

LEDs produce a very narrow spectrum of visible light without the losses to irrelevant radiation types (IR, UV) or heat associated with conventional lighting, meaning that most of the energy consumed by the light source is converted directly to visible light.

Incandescent lights emit a very small percentage of their emissions as visible light. A much larger portion is emitted as infrared (essentially heat). Unless you are trying to heat a room with your lightbulbs this is a generally negative feature of incandescent light.


Heat Emissions

LEDs emit very little forward heat. The only real potential downside to this is when LEDs are used for outdoor lighting in wintery conditions. Snow falling on traditional lights like HID will melt when it comes into contact with the light. This is usually overcome with LEDs by covering the light with a visor or facing the light downward towards the ground.

Incandescent lights emit roughly 90% of their emissions as heat. In some circumstances heat emissions could be beneficial, however, it is a generally a bad thing to emit heat as it represents an energy inefficiency. The ultimate purpose of the device is to emit light, not heat.


Failure Characteristics

LEDs fail by dimming gradually over time. Because LED lights typically operate with multiple light emitters in a single luminaire the loss of one or two diodes does not mean failure of the entire luminaire.

Incandescent lights generally hard fail meaning they stop working completely and all at once. Incandescent lights burn well throughout their lifetime but the extremely limited time of life (approximately 1,200 hours versus 100,000+ with LEDs) makes them a real bear with maintenance and replacement costs.


Foot Candles (Read More Here)

Foot candle is a measure that describes the amount of light reaching a specified surface area as opposed to the total amount of light coming from a source (luminous flux).

LEDs are very efficient relative to every lighting type on the market. Typical source efficiency ranges 37 and 120 lumens/watt. Where LEDs really shine, however, is in their system efficiency (the amount of light that actually reaches the target area after all losses are accounted for). Most values for LED system efficiency fall above 50 lumens/watt.

Incandescent light is generally very inefficient for two principal reasons: first, most of the electricity goes to generating heat. Second, the bulb is omnidirectional meaning a large portion of the emissions are lost to non-relevant areas other than the intended target.



LEDs last longer than any light source commercially available on the market. Lifespans are variable but typical values range from 25,000 hours to 200,000 hours or more before a lamp or fixture requires replacement.

Incandescent lights have the worst lifespan of any bulb on the market (roughly 1,200 hours). Typical lifespan values for an HID bulbs like HPS or CFL are around 10,000-24,000 hours (10-20 times as long). LEDs last 2-10 times as long as HID bulbs which means they last roughly 50-100 times as long as incandescent.


Lifetime Costs

LED lighting has relatively high initial costs and low lifetime costs. The technology pays the investor back over time (the payback period). The major payback comes primarily from reduced maintenance costs over time (dependent on labor costs) and secondarily from energy efficiency improvements (dependent on electricity costs).

Incandescent lights are by far the cheapest light to purchase on the market but they are a bear to maintain over time because their lifespan is so short. Incandescent lights will likely need to be purchased 20-50 times and the associated labor costs will need to be paid in order to attain the equivalent lifespan of a single LED light. Additionally, incandescent lights have the highest energy costs on the market.


Maintenance Costs

As a result of the operational lifetimes of LEDs and the frequency with which bulbs have to be changed out, LEDs are by far the best on the market in regards to lifetime costs.

Incandescent lights will likely need to be purchased 20-50 times and the associated labor costs will need to be paid in order to attain the equivalent lifespan of a single LED light.


Upfront Costs

LED light costs are high but variable depending on the specifications. The typical 100W-equivalent LED light costs somewhere between $10 and $20.

Incandescent lights costs vary depending on the specific type of light. They are cheap compared to LEDs ($1-$7 for a 100W bulb).

WINNER:  Incandescent

Shock Resistance

LEDs are solid state lights (SSLs) that are difficult to damage with physical shocks.

Incandescent bulbs are fragile relative to LEDs as they operate by using a filament encased by a glass bulb.



LEDs can be extremely small (less than 2mm in some cases) and they can be scaled to a much larger size. All in all this makes the applications in which LEDs can be used extremely diverse.

Incandescent lights come in all shapes and sizes but are typically used for indoor and residential applications where size isn’t a major factor. They can be small but not as small as an LED and they do not compare to the small size and robust build of a solid state light like LED.


Cold Tolerance

LEDs: Minus 40 Degrees Celsius (and they will turn on instantaneously).

Incandescent: Small delays at very low temperatures can exist as the bulb takes a little longer to warm up to a temperature where light is emitted.


Heat Tolerance

LEDs: 100 Degrees Celsius. LEDs are fine for all normal operating temperatures both indoors and outdoors. They do, however, show degraded performance at significantly high temperatures and they require significant heat sinking, especially when in proximity to other sensitive components.

Incandescent: We couldn’t find any objective data on incandescent bulb performance in high temperature situations. If you have any information please contact us.


Warm-Up Time

LEDs have virtually no warm-up time. They reach maximum brightness near instantaneously.

Incandescent lights don’t generally require a warm-up time but there can be a short delay as the filament heats up when operating at extremely cold temperatures.



LEDs: Often 5 to 10 years.

Incandescent: Typically N/A due to the short lifespan and low purchase price of incandescent lighting


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