The Coefficient of Utilization (CU) Calculator measures the efficiency of a lighting system in delivering usable light to a specified area. It is widely used in architectural, engineering, and lighting design to ensure effective illumination. The CU value indicates how much of the generated light actually reaches the target area, factoring in the light's reflection, absorption, and losses.
This calculator is an essential tool for optimizing energy use and ensuring compliance with lighting standards, especially in large commercial and industrial spaces.
Formula of Coefficient of Utilization Calculator
The coefficient of utilization is calculated using the following formula:
Where:
- CU = Coefficient of Utilization
- UF = Utilization Factor (accounts for the proportion of light reaching the target area)
- LLF = Light Loss Factor (accounts for losses due to factors like dirt accumulation, lamp lumen depreciation, etc.)
Steps to Calculate:
- Determine the Utilization Factor (UF):
This is typically provided in lighting design tables or calculated based on the room's geometry, surface reflectance, and luminaire placement. - Determine the Light Loss Factor (LLF):
LLF includes various loss factors like dirt on the luminaire, lamp lumen depreciation, and fixture degradation over time. It is expressed as a decimal. - Multiply UF and LLF:
The result gives the Coefficient of Utilization (CU), which is expressed as a decimal or percentage.
Table for Common Lighting Scenarios
| Utilization Factor (UF) | Light Loss Factor (LLF) | Coefficient of Utilization (CU) |
|---|---|---|
| 0.7 | 0.9 | 0.63 |
| 0.8 | 0.85 | 0.68 |
| 0.75 | 0.8 | 0.60 |
| 0.6 | 0.95 | 0.57 |
| 0.9 | 0.9 | 0.81 |
This table provides typical CU values for various lighting conditions, helping designers quickly estimate efficiency without performing detailed calculations.
Example of Coefficient of Utilization Calculator
Let’s calculate the coefficient of utilization for a lighting system:
- Utilization Factor (UF) = 0.75
- Light Loss Factor (LLF) = 0.8
Using the formula:
CU = 0.75 × 0.8
CU = 0.60
In this example, the Coefficient of Utilization is 0.60, meaning 60% of the generated light is effectively delivered to the target area.
Most Common FAQs
The Coefficient of Utilization determines how efficiently a lighting system delivers usable light to a specified area. It helps in optimizing energy use and ensuring the desired level of illumination.
The Utilization Factor depends on factors such as room geometry, surface reflectance, and luminaire placement. It is typically find in photometric reports or calculated using lighting design software.
Yes, by identifying inefficiencies in the lighting system, the calculator helps designers choose better fixtures and layouts, reducing energy consumption while maintaining adequate illumination.