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There are many details and concepts to keep track of when you have to compare LED bulbs and find just the right one. Concepts such as: RA, Lumen, Kelvin, Watt and so on. We understand if it all seems a bit confusing. So to help you through this jungle of LED concepts, we have created a list which should make it easier for you to find the LED bulb that fits your exact needs.


On this page you can find information about:

What is LED?

Which wattage shoul I choose?

The LED bulb's luminosity (lumens) compared with the incandescent bulbs’ power consumption ( Watts).

Energy Efficiency

Color rendering

Color Temperature: Kelvin (K)

Color rendering index: RA / CRI

Life expectancy


Beam angle

Socket / Base

How do I get light similar to incandescent bulbs?

Choose the right LED bulb - follow the advice of The Danish Energy Saving Trust

Learn more about LED bulbs


What is LED?

LED stands for Light Emitting Diode. There are many reasons to use LEDs for lighting purposes. They include incredible energy efficiency, long life, durability and of course they are very environmentally friendly. Until recently, there have been some limitations of using LEDs for general lightning purpose, particularly because the LEDs have not been sufficiently energy efficient, and color reproduction was not good enough. However all that have changed over the last few years. Today, LEDs are 5 times as energy efficient as incandescent bulbs, and color reproduction is about the same as fluorescent lighting. The LED bulbs available today can fully replace incandescent and halogen bulbs up to 40 W.


Which wattage should I choose?

An LED bulb gives about 8 times as much light per Watt as an incandescent bulb. To find out how many watts an LED bulb should have, compared to an incandescent bulb, you can use the ratio 1 to 8.This means that if you have a lamp that requires a 35 watt incandescent bulb, you can use a 4 watt LED bulb as replacement (35W / 8 = approx. 4W).

Incandescent Bulb                 LED Bulb

      20-30 W                                3-4 W

      30-40 W                                5-6 W

      40-50 W                                6-8 W


The LED bulb's luminosity (lumens) compared with the incandescent bulb’s power consumption (Watts)

How much light a bulb emits is measured in lumens (Im). Most LED bulbs emit very little light compared with eg incandescent light bulbs. The strongest single diodes can emit about 50-100 lumens which is about 1/7 of an incandescent bulb and only approx. 1 / 30 of the light output from a fluorescent tube. LED manufacturers have therefore begun to pack more diodes together, and can thus, produce light bulbs that can emit up to 1000 lumens.

The EU has made the following guidelines, so you can easily see how many lumens an LED bulb must have in order to replace an old incandescent bulb, measured in watts.

Incandescent Bulb (Watt)      LED (Lumen)

                100                              1300-1400

                 75                                  920-970

                 60                                  700-750

                 40                                  410-430

                 25                                  220-230

                 15                                    120


Energy Efficiency

When you compare the efficiency of different bulbs, you often use two main parameters: How much light the bulb emits (lumens) and the energy it uses (Watts). Efficiency expressed in lumens/Watt (Im / W) shows how efficiently the bulb converts the energy used into visible light. The most efficient white LEDs in the market have an efficiency exceeding 100 Im / W. LEDs are therefore 5 times as efficient as incandescent bulbs, 3 times as efficient as halogen lamps and about the same as compact fluorescent lamps, which typically has an efficiency of 50-60 Im / W.


Color rendering

One of the most important parameters that should always be considered when selecting bulbs is the color quality. In this respect the best LEDs are almost as good as halogen or incandescent bulbs, and in most cases at least as good as fluorescent and compact fluorescent lamps.

LED bulbs are available in a variety of colors: red, green, yellow, amber, orange, blue, cyan and several variations of these colors. By mixing the red, green and blue lights the LEDs can achieve virtually any imaginable color incl. white (RGB method). Another way to obtain the white light is by using a UV or blue LED with phosphor coating inside the LED. Both types are on the market in many different designs.

But when you talk about LEDs, white light is not just white light. There are different shades of white: cool white, neutral white and warm white. Color quality of these different types of white lights is defined by two parameters: The color temperature (color of light), measured in Kelvin (K) and the color rendering index (RA/CRI-index)


Color temperature: Kelvin (K)

As mentioned, there are three different categories of white light LED bulbs: warm, neutral and cool.


  • The warm white has a color temperature ranging from 2.700 - 3000 K
  • The neutral whites ranges from 3500 - 4500 K
  • The cool white ranges from 4500 - 10000 K



The warm white contains a little yellow, the cool white a little blue, and the neutral has no color added. Incandescent bulbs also emit a little yellow light. Warm white bulbs will therefore most resemble the light from ordinary light bulbs.


For everyday use in your home, we recommend a warm white bulb with 2700 – 3000 K.


Color rendering index: RA / CRI

The color rendering index has an RA value between 0 and 100 and says something about, how well the bulb reproduces the 8 reference colors. Daylight has the best color reproduction of 100, incandescent and halogen bulbs have a color rendering of 99 and compact fluorescent lamps and normal fluorescent lamps have a color rendering of a little over 80 RA. Fluorescent light is produced with Ra-values between 50-98 RA and is therefore available in versions with especially good color rendering that is almost as good as incandescent bulbs. By comparison, the best white LEDs have a RA-value of up to 95, which is close to halogen bulbs and the best fluorescent lamps.


For general lighting purposes, it is a good idea to buy bulbs that have an RA value of at least 80.


Life expectancy

The lifespan of an LED bulb is often between 25,000 and 50,000 hours, but depends largely on how you treat the LED. High temperatures and heavy current loads can strongly reduce the lifespan of an LED. There can also be really big differences between LEDs lifespan and quality from one manufacturer to another. Therefore it is important that you are aware of the conditions that you need to fulfill, for you to achieve long life for your LED bulbs.



LEDs illuminate instantly and provide full brightness from the start. Would you like a dimmable LED bulb, you should be aware that it must be specially designed for it. Most LED bulbs on the market do not contain the necessary electronics. Always look on the packaging, which will tell you if the bulb can be dimmed or not.


Beam angle

LEDs are best at creating directional light. LEDs send all the light forward, with dispersion angles from 5-140°, while most conventional bulbs emit light in all directions 360°. Therefore LED bulbs are best suited for lamps, which send the light in one direction. E.g. Spotlights and lamps, that only lights downward. To replace conventional round bulbs, producer therefore have to place the diodes so they radiate in different directions, or use some wide-angled diodes, though they are somewhat what more expensive than ordinary diodes.



What determines the socket/ base is of course the type of lamp you have. Different types of socket could be: spotlights, fluorescent tubes, pin bulbs, or regular ball shaped bulbs, (E14 LED = Small base, E27 LED = large base).


How do I get light similar to incandescent bulbs?

•  To mimic an incandescent bulb best the color should be warm-white (2700-3000K color temperature).
    In the office space you could go little higher up in temperature.

•  The Ra value should be 80 or higher.


Choose the right LED bulb

- Follow the advice of The Danish Energy Saving Trust

1. The LED bulb must have both the right socket and the right dimensions to fit a particular lamp.

     Not all LED bulbs can be dimmed or be incorporated into 12V systems.

2. The light must suit both the lamp and the light function.

     LED bulbs are often really good as spotlights because they can emit light in narrow light beams.

3. The light must be strong enough for the purpose.

     A 60 W incandescent bulb can, as of yet, not be replaced by LEDs, since they do not provide a sufficient amount of light.

4. Choose LEDs with good color rendering. The light from white LEDs can be both warm and cool.

     You get the best color rendering if the so-called color rendering index (the Ra/CRI index) is at least 80.


To learn more about LED bulbs

Visit these websites:

LED Light Bulbs Direct

The European Commission’s guide to choosing the right energy-saving light bulb