Lumens vs watts: lumens to watts conversion chart

Understanding Lumens vs. Watts in Lighting

Lumen and watt are two completely different concepts, belonging to the fields of optics and electricity, respectively. Here is a detailed introduction to these two concepts:

What is Lumen?

• Definition: Lumen (symbol: lm) is the derived unit of luminous flux in the International System of Units (SI). It is used to express the total amount of visible light emitted by a light source in a unit of time. Lumen takes into account the human eye’s varying sensitivity to different wavelengths of light, so its magnitude is influenced by the weighting of the photopic response function.
• Calculation Method: In 2018, the 26th General Conference on Weights and Measures (CGPM) redefined the candela, which came into effect on May 20, 2019. Its definition is as follows: for a monochromatic radiation source with a frequency of 540 × 10^12 hertz, the luminous efficacy K_cd is defined as 683 lumens per watt. This means that 1 lumen of visible light corresponds to at least 1/683 watts of power, with the specific value varying based on the frequency of the light source.
• Applications: In daily life, the luminous capability of electric light sources is typically indicated in lumens. For example, a 23-watt compact fluorescent bulb can provide between 1,400 and 1,600 lumens. In many regions, regulations require labeling lumens instead of watts to help consumers better understand the actual brightness of light sources.

What is Watt?

• Definition: Watt (symbol: W) is the unit of power in the International System of Units, used to express the rate of work done or the rate of energy transfer over time. In electricity, watts are commonly used to measure the energy consumption of appliances.
• Calculation Method: The formula for calculating watts is Power § = Voltage (V) × Current (I). For instance, a 120-volt power supply providing energy to a 1-amp appliance has a power output of 120 watts.
• Applications: Watts are widely used in various appliances and energy devices to indicate power ratings. For example, a 100-watt incandescent bulb consumes 100 watt-hours (0.1 kilowatt-hours) of electrical energy in one hour.

Lumen Vs Watt in Practical Applications

• Lighting Devices: When selecting lighting devices, lumens are an important reference index. For example, a light source with 1000 lumens illuminating an area of 1 square meter has an illuminance of 1000 lux; if the same 1000 lumens are spread over an area of 10 square meters, the illuminance would only be 100 lux.
• Energy Efficiency: Light sources with high lumen efficiency are more energy-efficient. For example, LED bulbs possess a much higher lumen efficiency than traditional incandescent bulbs, meaning that under the same brightness requirement, LED bulbs consume less electrical energy and have a longer lifespan.

From the above introduction, it can be seen that although lumens and watts both involve energy transfer, lumens focus on the energy of light while watts focus on electrical energy. The two concepts are closely related in practical applications, especially when selecting lighting devices and evaluating energy efficiency.

Lumens and Watts: Making the Connection

To understand how many lumens are required for a particular wattage of solar LED street light, we must consider Luminous Efficacy (lumens per watt). This metric indicates how effectively a light source converts energy into light:

Luminous Efficacy (lm/W) = Lumens (lm) / Watts (W)

Comparing Luminous Efficacy of Different Lamps

According to a 2013 report from energy.gov, various light sources achieve different luminous efficacies:

Luminous Efficacy: The unit is lumens/Watt (lm/W), which indicates how many lumens of light the light source can produce per 1 watt of electricity consumption. Different light sources have different light efficiency values, for example:

• Incandescent lamp: about 10-17 lm/W
• Halogen lamp: about 20-25 lm/W
• Fluorescent lamp: about 50-70 lm/W
• LED light: about 80-150 lm/W

This means that for the same wattage, LED bulbs can be 10-14 times brighter than incandescent bulbs and about 10 times brighter than halogen bulbs.

Lumens to Watts Conversion Chart

How to Determine Necessary Lumens

Lumen Calculator

To find the amount of lumens required for your needs, consider using a lumen calculator.

lumens to watts Conversion Formulas

Lumens to Watts

You can convert using the following formula:

Watts = Lumens / Light Efficiency (lm/W)

For example, if an LED light has a light efficiency of 100 lm/W and needs to produce 800 lumens of light, the required wattage would be:

Watts = 800 lumens / 100 lm/W = 8 Watts

Watts to Lumens

You can convert using the following formula:

Lumens = Watts × Light Efficiency (lm/W)

For example, if an LED light consumes 8 watts of power and has a light efficiency of 100 lm/W, the number of lumens produced would be:

Lumens = 8 Watts × 100 lm/W = 800 lumens

Application Example

Home Lighting: Suppose you need to choose a lighting fixture for the living room, which requires 1600 lumens of light. If you choose an LED light with a light efficiency of 100 lm/W, you will need a 16-watt LED light. If you choose a fluorescent light with a light efficiency of 65 lm/W, you will need an approximately 25-watt fluorescent light.

LED Light:

Watts = 1600 lumens / 100 lm/W = 16 Watts

Fluorescent Light:

Watts = 1600 lumens / 65 lm/W ≈ 25 Watts

How many lumens should outdoor solar lights have?

The lumen requirement forsolar lights varies based on factors like pole height, road width, and ambient light. Generally:

• Solar landscape light: 3000-5000 lumens, illumination requirements 10-100 lux
• Solar path light: 30-60 lumens, illumination requirements 5-10 lux
• Solar floodlight: 1000-3000 lumens, illumination requirement 10-100 lux
• Solar garden light: 50-100 lumens, illumination requirement 5-15 lux
• Solar trail light: 30-50 lumens, illumination requirements 5-10 lux
• Solar decorative lights: 10-30 lumens, illumination requirements 1-5 lux

What is Lux in Lighting? Solar Lighting Lux Level standard

How many lumens for Solar street lights?

Expressways

• Due to the high efficacy of LED streetlights, higher wattage LED lamps are generally needed to meet the illuminance requirements. For example, using 200-watt LED lamps can provide approximately 20,000 to 30,000 lumens of luminous flux.

Main Roads

• Suitable for using 100-150 watt LED lamps, providing approximately 10,000 to 22,500 lumens of luminous flux.

Secondary Roads

• Suitable for using 50-70 watt LED lamps, providing approximately 5,000 to 10,500 lumens of luminous flux.

Branch Roads

• Suitable for using 30-50 watt LED lamps, providing approximately 3,000 to 7,500 lumens of luminous flux.

Sidewalks, Commercial Pedestrian Streets, Residential Communities

• Since these areas have higher requirements for color rendering and visibility of individuals, the advantages of LED lamps are more pronounced.
• Suitable for using 30-50 watt LED lamps, providing approximately 3,000 to 7,500 lumens of luminous flux.

Recommended solar street light Lumens by Pole Height

For further guidance, refer to this article on how to calculate the height and distance of solar street light poles.

Lumens Needed for Indoor Spaces

Here are general lumen recommendations for various indoor environments:

• Garage/Workspace: 8,000 to 10,000 lumens
• Kitchen: 7,000 to 8,000 lumens (work area)
• Bathroom: 7,000 to 8,000 lumens
• Home Office: 6,000 to 8,000 lumens
• Dining Room: 3,000 to 4,000 lumens
• Living Room: 1,000 to 2,000 lumens
• Bedroom: 1,000 to 2,000 lumens
• Hallway: 500 to 1,000 lumens

Keep in mind that rooms with darker walls or high ceilings may require extra lumens.

Verifying Luminous Efficacy

To confirm the reliability of luminous efficacy claims, always refer to the manufacturer’s Luminous Efficacy Test Report.

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Reliable Sources for Further Reading

• https://luxmanlight.com/understanding-the-difference-between-watts-and-lumens-a-comprehensive-guide-to-choosing-the-right-brightness-for-your-lighting-fixtures/