1. What is a Lumens to Watts Calculator?

Definition: This calculator converts luminous flux (in lumens) to electrical power (in watts) based on the luminous efficacy of the light source.

Purpose: It helps compare different lighting technologies and estimate energy consumption based on light output.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( W \) — Electrical power (watts)
• \( \Phi \) — Luminous flux (lumens)
• \( E \) — Luminous efficacy (lumens per watt)

Explanation: The luminous flux is divided by the luminous efficacy to determine the electrical power needed to produce that amount of light.

3. Importance of Lumens to Watts Conversion

Details: This conversion helps in energy efficiency calculations, comparing different light sources, and estimating electricity costs for lighting.

4. Using the Calculator

Tips: Enter the luminous flux in lumens and the luminous efficacy (default 80 lm/W for typical LED). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is luminous efficacy?
A: It measures how efficiently a light source produces visible light (lumens per watt of electrical power).

Q2: What are typical efficacy values?
A: Incandescent: 10-17 lm/W, CFL: 50-70 lm/W, LED: 80-120 lm/W, High-efficiency LED: up to 200 lm/W.

Q3: How do I find the luminous flux of a bulb?
A: Check the product packaging or specifications - it's often listed alongside wattage.

Q4: Why convert lumens to watts?
A: To compare energy efficiency between different lighting technologies or to estimate energy costs.

Q5: Does this account for all energy consumption?
A: This calculates the theoretical power based on light output. Actual power may be slightly higher due to driver/ballast losses.