1. What is Luminous Efficacy (Lumens Per Watt)?

Definition: Luminous efficacy measures how efficiently a light source produces visible light, calculated as lumens per watt (lm/W).

Purpose: It helps compare energy efficiency of different lighting technologies and select the most efficient lighting solutions.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• Efficacy — Light output efficiency (lumens per watt)
• Lumens — Total visible light emitted (lm)
• Watts — Power consumed (W)

Explanation: Higher values indicate more efficient lighting, producing more light with less energy.

3. Importance of Luminous Efficacy

Details: Understanding lm/W helps in energy conservation, reducing electricity costs, and meeting environmental standards.

4. Using the Calculator

Tips: Enter the total lumens and power consumption in watts. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a good lumens per watt ratio?
A: Incandescent: 10-17 lm/W, CFL: 30-70 lm/W, LED: 50-150+ lm/W. Higher values are better.

Q2: Why measure efficiency in lumens per watt?
A: It standardizes comparison between different lighting technologies regardless of size or shape.

Q3: Can efficacy exceed 683 lm/W?
A: 683 lm/W is the theoretical maximum for pure green light. White light typically maxes around 300 lm/W.

Q4: Does this account for driver/power supply losses?
A: No, this calculates system efficacy if using total system watts. For chip-only efficacy, use LED wattage.

Q5: How does efficacy relate to energy savings?
A: Higher efficacy means more light per watt, directly reducing energy consumption for the same brightness.