420 Lumens to watts is typically 4.7 watts using LED, but is dependent on the efficiency of the light source.
The outdated metric of using wattage to judge brightness is over, as LED lights use less power to produce the same amount of lumens and can differ according to design. So a new comparison needs to be made.
To known what is 420 lumens in watts, use each light source’s watts to lumens efficacy, typically:
Not all LEDs require the same amount of power to create the same light output. Here are some example products and their corresponding wattages:
A 420 lumens B10 / B11 LED bulb will use 3.56 Watts @ 118 lm/W
420 lm LED Spot GU10 2700K PAR16 uses 4.47 Watts @ 94 lm/W
A 420 lumens A19 2700K LED bulb will use 4 Watts @ 104 lm/W
An 420 lumen recessed ceiling light requires 5.45 Watts @ 77 lm/W
A recessed downlight with an 420 lumen output requires 4.2W of circuit power @ 100 lm/W
A 4.8 W/m 70 LED 3000K strip will use 4.94 Watts to create 420 lm @ 85 lm/W
As lumens measure the amount of light and watts the amount of power used to create that light, now efficiency is considerably better with LED, the wattage has become an outdated benchmark for brightness as a small amount of power will now create a lot of lumens.
To convert 420 lumens to watts, we first need to know the efficacy of the light source.
Efficacy is a measure of how well a light source produces visible light. It is measured in lumens per watt (lm/W) or light output per watt.
A higher efficacy means more light for the same amount of power, with different light types and even different models within a light type varying quite a bit.
For reference, here are some average lm/W efficacies for various light types:
So now a more accurate lumens to watts calculation is required to find out how much power your LED light will consume.
The power in watts (W) is equal to the luminous flux in lumens (lm), divided by the luminous efficacy in lumens per watt (lm/W):
Watts = Lumens / Efficiency
For example, an LED with an efficiency of 80 lumens per watt would require 5.25 watts to produce 420 lumens.
420 lumens / 80 lumens per watt = 5.25 watts
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