The Ultimate Guide to Key Lighting Parameters


LEDs have gained popularity in the 21st century due to their ability to produce the right amount of light while consuming less energy. When purchasing fixtures or lighting design, most people will refer to the wattage to see how much power an LED fixture needs to be as bright as it needs to be.

Wattage refers to the amount of energy required by a fixture to produce a certain amount of light. Generally speaking, the higher the wattage, the brighter the light. However, there are a lot of lamps especially solar lamps, some sellers claim that the power reaches 100W or even 1000W or more, but the real constant power is far from that, which is a deliberate act to mislead consumers.

Therefore, we believe that an understanding of these lighting parameters will help to enhance the knowledge of lighting designers and general consumers about LED lights.

What is Watt?

Named in honor of James Watt, a British scientist who contributed significantly to the development of the steam engine, the watt was first adopted by the 2nd meeting of the British Association for the Advancement of Science in 1889, and then officially adopted by the 11th meeting of the International Conference on Weights and Measures in 1960 as the unit of power in the International System of Units (SI unit).

In the electrical system of units, the watt can also be expressed as the volt times the ampere (1V-A, or 1 volt-ampere), which is used to measure the energy consumed by a lighting device.

In the days when incandescent bulbs were commonly used, it was common for people to buy 100-watt bulb to light up a room. Gradually, the brightness of 100-watt bulb was used as a reference standard for brightness.

The End of 20th Century

Because the photoelectric conversion efficiency of incandescent bulbs is too low, at the end of the last century, tri-phosphor powder compact energy-saving lamps(CFL) began to gradually replace incandescent bulbs. The conventional luminous efficacy of CFL can reach more than 80 LM/W, while incandescent lamps are generally below 15 LM/W.

The Early of 21st Century

In the early 21st century, the advantages of LED lights began to arrive, as it has a higher luminous efficiency and longer service life. Conventional LED panel light efficacy can reach more than 150LM/W, and the average service life can reach as long as 10 years. Therefore, CFL has been gradually replaced by LED light.

Although the lamps are constantly evolving, the wattage as one of the most important parameters has been continued until now. People are accustomed to using the brightness of a 100W traditional incandescent bulb as a reference value to assess how many watts of a new lighting species need to be purchased.

wattage introduction

However, wattage doesn’t tell you how much light is really being produced, which is where another unit of measurement comes in – lumens. A lumen is a unit of measurement for the amount of luminous flux emitted by an LED light, and it allows you to compare the brightness of different fixtures (under the same operating conditions).

What is lumen?

Lumen is a physical unit that describes luminous flux, which represents the total amount of visible light emitted by a light source per unit of time. The greater the lumen value of a light source (e.g., LEDD bulb, LED panel light, etc.), the brighter the light it emits.

Lumens are related to the unit of luminous intensity, the candle. The total emitted luminous flux produced by a candle of light at a three-dimensional angle (the angle represented by the cone corresponding to the crown of a sphere of 1 square meter on a unit sphere with a radius of 1 meter, which corresponds to the central angle of the middle section of the circle of about 65 °) is a lumen.

It is important to note that lumens only represent the total amount of light emitted by a light source without regard to the directionality of the light. For a directional light source (such as a flashlight or spotlight), the lumen value is the same, but the brightness will be more concentrated in a smaller area due to the focusing effect of the light. Therefore, the angle of luminosity is also one of the important parameters to be considered when lighting design.

Luminous Flux

Luminous flux is the most direct embodiment of the brightness of LED light, when purchasing LED lighting source can take the luminous flux as the most primary consideration, rather than the nominal power. Determine the required luminous flux, and then go to choose a lower wattage products. The lower the wattage, the better the energy savings.

Wattage and lumens are two widely used indicators of light output. The lighting effect produced by a fixture after installation is measured in Lux. We can use lighting simulations or illuminance meters to determine the illuminance effect of a lighting environment.

What is Lux

Lux is the unit of illuminance, when the luminous flux received by an object uniformly illuminated by light, on an area of 1 square meter is 1 lumen, its illuminance is 1 lux. It is used to describe the intensity of the luminous flux received per unit area.

What is Maintenance Factor

The maintenance factor is a parameter used in lighting design that takes into account the luminous flux degradation of a fixture over the course of its use, which is mainly due to the accumulation of dust, aging of the light source, etc. The maintenance factor is the ratio of the actual luminous flux of a fixture to its initial luminous flux.

Therefore, the maintenance factor can be regarded as the ratio of the actual luminous flux of a fixture to its initial luminous flux after a period of use. Generally speaking, the maintenance factor of indoor fixture is between 0.7 and 0.8.

Relationship of Lux to Lumens (lm) and Candela (cd)

Lux is the unit derived from lumen, while lumen is the unit derived from candela.

  • The candela is the unit of luminous intensity and indicates the luminous flux emitted by a light source in a given direction per unit steradian angle.
  • Lumen is the unit of luminous flux, indicating the light energy emitted by a light source in a unit of time.

  • Lux, on the other hand, is the unit of illuminance and indicates the intensity of luminous flux received per unit area.

Relationship between Lux, LM and Maintenance Factor

In the field of lighting engineering, illuminance is an important design index, which can be illustrated by a simplified formula for general consumers:

LED lighting parameters relationship

Luminous Flux = (Illuminance Value x Number of Lights) / Maintenance Factor

For example, in hospital lighting design, the average illuminance of the treatment room needs to be more than 300Lux. If the room area is 20 square meter, the maintenance factor of the lamps is 0.8, then the required luminous flux = (300lux * 20)/0.8 = 7500 lm. This will probably require 2 pieces of 26W LED panel lights (150lm/ w).

As can be seen from the formula, in order to obtain higher illuminance levels (e.g. a laboratory needs at least 500 lux or more), the power or number of lights need to be increased in order to achieve the required lux level.

For more details on hospital lighting design, please visit:

What is Luminous Efficiency

In lighting, luminous efficiency is the ratio of luminous flux emitted by a light source to the electrical power consumed, in lumens/watt.

Luminous Efficiency = Luminous Flux / Wattage

It reflects the ability of a fixture to convert electrical energy into light energy. The higher the luminous efficacy, the more energy efficient the fixture is in providing the same brightness; the higher the luminous efficacy, the greater the brightness under the same power.

For example, if the luminous flux of a 10W solar tube light is 900LM, then its luminous efficacy = 900/10 = 90lm/w; It should be emphasized that this wattage is the wattage of the whole lamp, not the wattage of the LED beads.

Special attention should be paid to the fact that poor quality driver will consume a lot of power, which will lead to the light efficiency of the whole lamp is very low. Therefore some sellers only label the light efficiency of the LED beads and deliberately hide the light efficiency of the whole lamp, claiming that their lamps are featured by high light efficiency, which is a misdirection.

Relationship between Luminous Efficiency and Lux

Illuminance is a measure of the amount of light received on a surface. To calculate the illuminance of a light source on a surface, you need to know the luminous flux of the light source, the distance from the light source to the surface, and the angle at which the light source shines.

Luminous efficiency measures the ability of a light source to convert electrical energy into light energy. It is the value obtained by dividing the luminous flux emitted by the light source by the electrical power consumed.

They are two different physical quantities, so there is no direct conversion relationship between them.

Important Parameters of Lamp Components

LED Beads


The BIN of a LED bead can also be referred to as bin code, i.e. classification code. It refers to the different classification or range of characteristic parameters such as brightness or color of LED beads. In the LED manufacturing process, due to the material, process and other factors, the brightness, color and other characteristics of each LED bead will be different.

In order to standardize and classify these differences, the concept of BIN is introduced. When selecting and using LED light beads, you need to choose the right BIN value according to your actual needs and budget.

For example, the following charts show the BINS of a CREE LEDs (Model CLA1B):

cree LED bins 1
cree LED bins 2
Cree LED Bin 3

Color Temperature

Color temperature, used to describe the color of light emitted by a light source and the blackbody at a certain temperature when the color of the light radiated by the same temperature, in Kelvin (K).

Color temperature can be divided into the following categories:

1. Warm Tones:

usually below 3300K, the light source is yellowish, belongs to the warm color, gives a person a feeling of warmth, comfort, create a warm, comfortable atmosphere, applicable to the bedroom, living room and other places.

2. Middle Tone:

usually between 3300K and 5300K, the light source is softer, the light is similar to the natural light, make people feel clear, natural, suitable for reading, learning and other places that need clear vision.

3. Cold Tone:

usually above 5300K, the light source is white, belongs to the cold tone, gives a person a feeling of more cold, refreshing, invigorating, applicable to the need to work efficiently or need to stay focused on the place, such as offices, conference rooms and so on.

In the field of lighting, the following chart shows the common interval band of color temperature.

Color Temperature 01

Color Rendering Index

The color rendering index is a measure of the ability of a light source to reproduce the color of an object. Its value ranges from 0 to 100, the higher the value, the better the ability of the light source to restore the color of the object, the more realistic the color.

In the regulations of the International Commission on Illumination (CIE), Planck radiant is regarded as the ideal reference light source, and its color rendering index is set at 100. Besides, sunlight or incandescent lamps are also regarded as the ideal reference light source, and their color rendering index is also defined as 100.

In certain situations where accurate color reproduction of objects is required (e.g., fabric stores, museum lighting, etc.), a high color rendering index of 95 or higher should be considered.

Color Rendering Index

Relationship between CRI and Luminous Efficacy

There is a certain mutual restriction between color rendering index and luminous efficacy. The color rendering index is mainly related to the phosphor material and ratio of the package. Higher color rendering indices usually require a wider spectrum, which results in a loss of light energy and thus lower luminous efficacy.

On the contrary, light sources with higher luminous efficacy focus more on improving the utilization of light energy and make some compromises on spectral richness, resulting in a relatively low color rendering index.

However, by optimizing the materials and ratios of LED wafers and phosphors, it is possible to achieve a high color rendering index while ensuring high luminous efficacy. But it will become costly.

It should be noted that the relationship between color rendering index and luminous efficacy should be balanced according to the specific application requirements during lighting design. In some lighting applications that require high energy efficiency (e.g., street lighting, warehouse lighting, etc.), more attention is paid to the luminous efficacy.

Heat Dissipation

The main role of heat dissipation is to absorb and distribute the heat generated by the LED chip. It mainly relies on heat conduction and heat convection to quickly conduct and distribute this heat into the air to ensure that the LED chip works at a suitable temperature.

For more information about the principle, structure, material and optimization of heat dissipation, please visit:

LED Driver

LED drive includes AC drive and DC drive. AC drive is a kind of electronic equipment that converts AC power into DC power suitable for LED light beads. It usually includes rectifier circuit, filter circuit, constant current circuit and other parts. And DC driver usually has constant current or low voltage constant voltage characteristics, such as solar lights or USB lights.

The driving for LED lights needs to consider factors such as driver efficiency, power factor, and electromagnetic compatibility.

Driver Efficiency

Driver efficiency refers to the power supply will be converted to the input power output power capacity, the formula is usually: driver efficiency = (LED lamp output power / input to the drive power supply electric power) × 100%.

For example, 30W standard wall washer light, using 2 different driver test the actual output power were 27W and 24W, then their driver efficiency is 90% and 80%. The higher the value, the more efficient the driver power supply will be the input electrical energy into the light energy, thereby reducing the loss and waste of energy. This has a significant energy saving effect on public lighting such as LED street lights and LED architectural lighting for high volume applications.

Power Factor

Power factor reflects the efficiency with which the power supply utilizes electrical energy. A high power factor reduces reactive power losses and improves the utilization of electrical energy. In addition, it can reduce harmonic interference to the grid, which is conducive to the stable operation of the grid.


Electromagnetic compatibility refers to the impact of electromagnetic interference generated by the power supply in the working process on other equipment.

In lighting design, if there are high-precision instruments in the environment where the lamps are used, such as hospitals with a large number of sensitive medical equipment and precision instruments, the EMC of the lamps is a very important consideration. This is because LED lamps generate too much electromagnetic interference, which may affect the normal operation of medical equipment.

In the EU market, EMC testing requirements are as follows:

1.Conducted Disturbance:

This is a measure of the electrical equipment in the normal operation of the process of the electromagnetic interference generated by the environment where it is located whether it exceeds a certain limit value of the standard. Test standards include EN 61000-3-2 and EN 61000-3-3.

2.Disturbance Power:

This is also a measure of electromagnetic interference.

3.Radiated Disturbance:

This is a measure of whether the electromagnetic disturbance emitted by electrical equipment in the form of electromagnetic radiation exceeds a certain limit. Test standards include EN 55032 and EN 55035.

4.Harmonic Current Emissions:

This is a measure of the harmonic component of the current generated by electrical equipment. Test standards include EN 61000-3-11 and others.

In addition, for electromagnetic immunity (EMS), the EU EMC Directive also has the corresponding test standards, mainly considering products such as electrostatic discharge, radiation immunity, electrical fast pulse group, surge, conduction interference tolerance.

For more articles on LED light drivers, please visit:


LED lamp lens is mainly made of PMMA (commonly known as acrylic) and PC (polycarbonate). Its main role is to enhance the luminous efficiency of LED lights, change the lighting distribution.

PMMA lenses have higher light transmission performance than PC lenses, but their high temperature resistance is relatively weak. PMMA material are usually used in high-end lighting, such as the light guide board of edge-lit LED panel lights. PC material are usually used in high-power lamp beads, such as wall washer lighting. The material cost of PC  is usually lower than PMMA , so it is more widely used.

Energy Efficiency Label

An energy efficiency label is an informative label attached to an energy-consuming product or its smallest package. Its main role is to help and guide consumers to purchase energy-efficient products. It is a necessary reference for purchasing decision.

Energy Efficiency Lable of EU Market

In the EU, energy efficiency labeling is a mandatory requirement for all types of lighting products, including AC LED lights. Such labels will indicate the energy efficiency level of the product as well as other performance indicators, such as energy consumption and light efficiency.

According to this regulation, lighting products entering the EU market must have an energy efficiency rating label attached to the product and be registered in the European Energy Labeling Products Database (EPREL). Below is a demonstration of the label in color and black & white.

ErP Label

The mandatory information is:
I The name or trademark of the supplier
II Model of the product
III Energy efficiency class A to G
IV Energy consumption of the light source, expressed in kilowatt-hours per 1000 hours of power consumption
V QR code
VI Energy efficiency in accordance with the class
VII Regulatory number 2019/2015

New energy regulations have increased the requirements for light efficiency. As a professional manufacturer of LED lighting, we have been developing new products to meet the requirement of high light efficiency. Currently, some of our models of wall wash lights and LED panel lighting have already achieved a luminous efficacy of 170LM/W.


This article describes the common parameters of LED lighting such as wattage, lumens, illuminance and luminous efficacy, as well as the relationship between them.

In addition, the functions and important parameters of each component of LED lamp are specified. Finally, the latest rules for energy efficiency labeling are explained in detail. These are the basic concepts that need to be mastered when designing lighting or purchasing them. For more details, please contact us.

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