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How to Choose LED Light Bulbs

How do I decide which LED bulb fits my needs?

In fact on closer inspection, the answer is not trivial, because in recent times several new models produced by different manufacturers have appeared on the market. Then we try to shed light on the situation, examining the main parameters on which we must focus before you buy the LED bulb.

In particular, we refer to:

  • Light intensity;
  • Energy Efficiency Class;
  • Color temperature;
  • Color Rendering Index;
  • Bulb non-directional/directional;
  • Lamp life;
  • Number of on/off cycles …

As we see, there are many magnitudes and surely increase in performance, will also increase the cost of the light bulb. Then we will have to find the right compromise between performance and cost.

It should be said that, with the entry into force of  EU Regulation 1194/2012, as of September this year, LED bulbs have to meet specific functional requirements which we will explain in the following article. Many models put on the market satisfy them from the outset.

How to Choose LED Light Bulbs

LIGHT INTENSITY 

Surely the light intensity is the first parameter to be considered, as it indicates the level of illumination we want to achieve in our environment. Then we try to figure out how to choose the light intensity.

Most of us are still accustomed to thinking in W, remembering that, when they were marketed almost solely incandescent bulbs, you made need not be taken as a reference light intensity.

Now, the LED bulbs, it has a much higher light intensity, or, said in an equivalent manner, with the same produced luminous intensity, consume far fewer W.

To facilitate the purchase, manufacturers typically bring in packages of light bulbs the comparison between their power consumption in W and the consumption at the old incandescent bulbs.

ENERGY EFFICIENCY CLASS

The indicators on the energy efficiency class is not too complicated, at least if we just interpret the meaning of the letters without going deep into how both calculated the energy efficiency index, also known as Energy Efficiency Index or EEI, which yields the class itself.

In general, it is good to know that today, for light bulbs on the market, the energy efficiency rating of A ++ to get to C. In fact bulbs with lower efficiency may no longer be marketed. Despite this, the graphics of the label still shows the classes below the C.

To be more precise, since September 2013 there are two types of energy labels, following the entry into force of the provisions of EU Regulation 874/2012, which provided for the introduction of new energy label for revenue bulbs on the market after this date. This means that we are faced with the coexistence between an old energy label for light bulbs put on the market before September 2013, and a new label. Let us see what are the main differences.

As we can see, the old energy label consisted of a first panel showing the scale of energy efficiency classes, with letters from A to G , although nowadays cannot be commercialized class bulbs less than the D (from 2016 onwards, for effect of the introduction of more stringent requirements for halogen lamps, provided for by Regulation 244/2009 , even the light bulbs in class C and D may no longer be marketed in fact). The new label has introduced the classes A ++ and A +, to account for the improvement in the efficiency of lighting technologies that occurred in recent years. In the new label, also in the upper part, marked with the symbols I and II in the image on the right, are shown the model and manufacturer. In the lower part we find a different mode of indication of fuel consumption and bulb performance. On the left, they are indicated in both the intensity of light output (expressed in lumens), both the consumed power, both the rated life of the lamp. In the new label is only reported annual consumption estimated for 1000h of use. On second thought this is entirely equivalent to the in W wattage in the old label, since dividing 1 kWh per thousand hours, you just get a W. This means that the new label displays less information (light intensity, useful life) than the old one, so we’ll go there to read the other features in the product box.

As regards the technologies available on the market, we can recognize that:

– The halogen bulbs (also called “improved incandescent”), are in Class D or C;

– CFLs (Compact Fluorescent Lamp or CFL), are class B or A;

– LED bulbs are in class A, A + or A ++;

So we already know that, when we go to buy an LED bulb, you’ll actually choose among the best available technologies in terms of luminous efficiency!

COLOR TEMPERATURE

In the case of LED, we will find in the box, alternatively the words “warm white”, “neutral white light” or “cold white light”. The UNI 12464 classifies three categories according to these values:

– Warm white -> color temperature <3300 K (Kelvin);

– Neutral white light -> color temperature between 3300 and 5300 K;

– Cool white -> color temperature> 5300 K;

Personally, for housing I would prefer a warm white light, more suited to environments where they prefer creating atmosphere rather than create more “sharp lighting conditions”, not to say dazzling, suitable for offices and contexts where it requires more attention and precision in the works.

In this regard, it should be noted that until recently, the luminous efficiency of warm white light LED was lower than the corresponding cold-light (just to have a yardstick, about 60 lumens / W at 73 lumens/W, see for example here). This is because the technique used to produce the white, both cold and hot, was based on the conversion of light emission of blue / UV LED (which then also emit uv, while the models currently on the market tend not emit) converted into white through a mixture of phosphors.

Now, however, they have spread to white light LED that exploit the combination of the basic colors from the individual LEDs, such as RGB colors.

OF COLOR RENDERING INDEX

The color rendering index, or Color Rendering Index (CRI), expresses the ability of a light source to return the colors “natural” the illuminated objects. For natural we want to indicate how the colors appear when illuminated by a reference light source, which, in simplified terms, and make the idea, we say it is represented by the diffuse light provided by the sun in a clear sky day.

In this regard, the lights in warm white LEDs typically have a CRI> 80, considered it more than suitable for home environments to render colors well (even though it will never reach the values ​​of an incandescent bulb, which has a spectrum of much more “dense light emission” and reaches the CRI values ​​close to 100). In the cold white LED lights tend to have lower CRI values.

Moreover, the new EU Regulation 1194/2012 , provided that, for the new LED bulbs put on the market and not intended for outdoor use, it will be obligatory a CRI> 80.

BULB NOT DIRECTIONAL/DIRECTIONAL

Obviously, when we buy our LED bulb for our living room or to illuminate the dining table, we have to make sure that it is a non-directional light bulb.  A directional lamp is a lamp that has at least 80% light output within a angle of 120°, vice versa for a non-directional.

This means that the non-directional bulbs allow a more diffuse illumination of the surrounding environment.

LIFE OF THE LAMP

Here we want to specify that, as stated in  EU Regulation 1194/2012 , for lamp life means:

“Lamp life”, the operating period after which the fraction of the total number of lamps which continue to operate corresponds to the lamp survival factor, under certain conditions and with a certain frequency of ignition; For LED lamps, the lamp life is the operation time between the beginning of its use and the time at which survives only 50% of the total number of lamps or the maintenance of the luminous flux the mean of the sample passes below the threshold of 70%, whichever condition occurs first.

So, it is said, among other things, that under the threshold of 70% of the luminous flux of the lamp, this is considered to have ceased their function. In fact, if for us a lower flow is acceptable, or if we can adapt the moving bulb in another domestic environment where it will be appropriate, this may still work for a long time.

According to the above, the LEDs on the market report typically between 25,000 hours and 50,000 hours life times, or about 25 times and 50 times higher than incandescent bulbs.

NUMBER OF CYCLES ON/OFF

As regards the number of on/off cycles, said more simply ignition cycles, always the EU Regulation 1194/2012 establishes that the new LED bulbs on the market must have a number of cycles ≥ 15,000 if the rated life of the lamp is ≥ 30,000 hours, otherwise, must be ≥ to half the rated lamp life expressed in hours.

All of the LED bulbs containers of different brands contain the given luminous intensity, expressed in lumens, or on the front or the back, or from both sides.

At the same time, the bulbs still report the data concerning the correspondence between the wattage consumed by the LED lamp and the power consumed by the corresponding incandescent bulb, so if you are more comfortable with this, you can take it as good reference.

As for the color temperature, on the packaging of the bulb, you will find both the words “white light warm/cool/neutral”, both the value expressed in degrees Kelvin, the latter sometimes only on the back and not the front.

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