In today’s world, lighting plays a vital role. Whether at home, in the workplace, or in public spaces, proper lighting not only enhances the beauty of the environment but also significantly impacts people’s health, performance, and comfort. But how can you accurately perform a lighting calculation for any space? In this comprehensive guide from EDC, we teach you the lighting calculation formula in simple, practical language. By understanding the basic concepts and relevant formulas, you can easily provide the required light per square meter and prevent wasting your capital and energy.
What Is Power Consumption?
Power consumption, measured in watts (W), indicates the rate at which an electrical device converts electrical energy into other forms of energy such as light, heat, or motion. Understanding power consumption is essential for any accurate lighting calculation.
To better understand the concept of power consumption, consider the following example:
Suppose you have a 100-watt incandescent bulb. This bulb converts 100 joules of electrical energy into light and heat every second. Now consider a 10-watt LED bulb. This bulb converts 10 joules of electrical energy into light every second.
As you can see, although both bulbs produce 100 units of light (lumens), the LED bulb requires less electricity due to its higher luminous efficacy. This is a key factor in any lighting calculation.
Why Power Consumption Matters
- By choosing low-consumption bulbs and optimizing electricity usage, you can significantly reduce your costs.
- More importantly, electricity generation resources are limited, and using low-consumption bulbs helps preserve natural resources and reduce environmental pollution.
- Accurate power consumption data improves the accuracy of your lighting calculation.
Candela and Lumen: Key Units in Lighting
In the world of lighting, there are two common measurement units for light: lumen and candela. Each of these units has its own specific application, and understanding their differences is essential for correctly selecting light sources and performing a lighting calculation for any space.
What Is Lumen?
Lumen is the unit for measuring luminous flux, or in other words, the total amount of light emitted by a light source per second. For example, a 100-watt incandescent bulb produces about 1,500 lumens of light. The higher the lumen value of a light source, the brighter that light source will be.
What Is Candela?
Candela is the unit for measuring light intensity in a specific direction. For example, a 10-watt LED bulb can produce light with an intensity of 1,000 candelas in its direct beam angle. The higher the candela value of a light source, the more concentrated its light will be.
Lumen vs Candela: What’s the Difference?
| Feature | Lumen | Candela |
|---|---|---|
| Measurement | Luminous flux (total amount of light) | Light intensity in a specific direction |
| Application | Measuring the overall brightness of a space | Measuring the concentrated light of a light source |
Lumen vs Power Consumption
Simply put, power consumption indicates how much electricity a device uses per second. Note that lumen and candela are independent units and have no direct relationship with energy consumption (watts). However, both are essential inputs in a complete lighting calculation.
Comparison of Lumen, Candela, and Power Consumption
| Bulb Type | Power Consumption (W) | Luminous Flux (Lumen) | Light Intensity (Candela) |
|---|---|---|---|
| LED 10W | 10 | 1,000 | 1,000 (in direct angle) |
| Incandescent 100W | 100 | 1,500 | 225 (in direct angle) |
| CFL 15W | 15 | 800 | 133 (in direct angle) |
Note: Luminous efficacy (lumens per watt) indicates how efficiently a light source converts electrical energy into light. The higher the luminous efficacy of a light source, the less electricity it requires. This directly affects the result of your lighting calculation.
Light Output per Watt: Efficiency Explained
The table below shows the approximate luminous efficacy of different types of bulbs:
| Bulb Type | Luminous Efficacy (Lumens per Watt) | Advantages | Disadvantages |
|---|---|---|---|
| LED | 80 to 150 | Very low consumption, long lifespan, wide range of light colors | Relatively high price |
| CFL | 50 to 80 | Low consumption, medium lifespan, moderate range of light colors | Contains mercury (toxic) |
| Incandescent | 10 to 15 | High consumption, short lifespan, limited range of light colors | High heat generation, short lifespan |
Suppose you need 2,000 lumens of light to illuminate a room.
- If you use an LED bulb with a luminous efficacy of 100 lumens per watt, you will need 20 watts of bulb (2,000 lumens ÷ 100 lumens per watt = 20 watts).
- If you use an incandescent bulb with a luminous efficacy of 13 lumens per watt, you will need 154 watts of bulb (2,000 lumens ÷ 13 lumens per watt = 154 watts).
As you can see, using a high-efficacy LED bulb reduces electricity consumption by up to 87%. This is why luminous efficacy is a critical factor in every lighting calculation.
Standard Light Levels (Lux) for Common Spaces
The table below shows the standard light levels for some spaces:
| Space | Approximate Area (m²) | Standard Light Level (Lux) |
|---|---|---|
| Living Room | 20 | 100 to 200 |
| Bedroom | 15 | 50 to 100 |
| Kitchen | 10 | 200 to 300 |
| Bathroom | 8 | 100 to 200 |
| Study Room | 12 | 300 to 500 |
| Office | 15 | 400 to 500 |
| Retail Store | 30 | 300 to 500 |
| School | 40 | 300 to 500 |
| Hospital | 30 | 200 to 400 |
Notes:
- Surface colors: Light surfaces reflect more light and require less light, while dark surfaces absorb light and require more light.
- Ceiling height: Spaces with high ceilings require more light than spaces with low ceilings.
- Window presence: If a space has natural light, you can reduce the amount of artificial light required to some extent.
These factors directly influence your lighting calculation.
How to Calculate Required Light for Any Space
Performing a lighting calculation for any space plays an essential role in creating a beautiful and safe environment. By considering the needs of the intended space, the type of activity, and the dimensions of the environment, appropriate light can be provided for any space.
Step 1: Determine the Space Type
- Specify the type of space (residential, office, commercial, industrial, educational, etc.).
- Consider the exact use of the space (bedroom, study room, kitchen, store, workshop, etc.).
Notes:
- The required light level for each space varies according to the type of activity and its use.
- For example, studying or performing precise tasks requires more light than a bedroom.
Step 2: Calculate the Area
- Calculate the area of the space in square meters.
- For non-rectangular spaces, calculate the area using the relevant formulas (triangle, circle, etc.).
Notes:
- Accuracy in calculating the area plays an essential role in determining the required light level.
- If there are unusable surfaces in the space, subtract their area from the final calculation.
Step 3: Determine Standard Lux
- Use standard light level (lux) tables for different spaces.
- For example, the standard light level for a living room is 100 to 200 lux.
Step 4: Calculate the Light Loss Factor
The light loss factor indicates how much of the light produced by the bulbs reaches the intended surfaces.
- This factor depends on the type of space, the type of bulb, and their arrangement.
- The following values are considered for the light loss factor:
- 0.8 to 1: For residential spaces with standard ceilings
- 0.6 to 0.8: For office and commercial spaces
- 0.5 to 0.7: For industrial spaces with high ceilings
Notes:
- Choosing the appropriate light loss factor prevents light waste and wasted costs.
- If you do not know the exact light loss factor for a space, you can use the approximate values provided above.
Step 5: Use the Lighting Calculation Formula
Use the following formula to calculate the total required light:
Total Light (Lumens) = Area (m²) × Standard Light Level (Lux) × Light Loss Factor
Example: Suppose we want to calculate the required light for a 20 m² living room with a standard ceiling. According to the table, the standard light level for a living room is 150 lux. We also consider the light loss factor to be 0.8.
Total Light (Lumens) = 20 (m²) × 150 (Lux) × 0.8 = 2,400 Lumens
Step 6: Choose the Right Bulb
Based on the calculations performed in the previous step, you can also determine the number of bulbs required.
To do this, divide the total required light by the luminous efficacy of the selected bulb.
Example: In the previous example, we needed 2,400 lumens of light and were using LED bulbs with a luminous efficacy of 100 lumens per watt.
Number of Bulbs = 2,400 Lumens ÷ 100 Lumens per Watt = 24 Watts
Conclusion
In this guide, the general method for performing a lighting calculation for any space and the formula for calculating the lighting of a space have been presented. For more precise calculations and professional lighting design, you can seek help from lighting specialists. EDC offers design and calculation services free of charge to its customers. EDC specialists help you choose and purchase the best lighting products according to your desired space and taste.