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Personal: Residential

Residential Lighting –
Lumens and Watts

When buying light bulbs, most people think of "watts" as a measure of brightness. We know, for example, that a 100-watt incandescent bulb can light up a room, while a small 7-watt bulb can serve only as a night light or a decorative light for the festive season.

In reality, the watt is a measure of energy, not of light output. A 40-watt bulb uses 40 watts of electricity no matter what type of bulb it is. But the amount of light produced by the bulb can vary significantly depending on its type.

Light output is measured in "lumens." A standard 100-watt incandescent bulb produces about 1680 lumens, whereas a compact 25-watt fluorescent lamp produces about 1750 lumens. While the two bulbs produce virtually the same amount of light, the compact fluorescent lamp does so using only a quarter of the energy consumed by the standard incandescent.

This means that fluorescent lamps are more energy efficient than incandescent ones, so it is important to choose the amount of light or "lumens" needed for a specific application and to verify the amount of "lumens per watt" as a measure of energy efficiency.