Laser engraver power explained: optical output vs electrical power
Why diode laser engravers are sold as 20W, 40W or 80W when their optical output is a fraction of that, what optical power means for cutting, and how to compare machines fairly.
Diode laser engravers are sold as 20W, 40W, even 80W machines. Two machines with the same headline wattage can cut very differently, because brands do not all mean the same thing by "power".
Two numbers called power
A laser module has an electrical power, what it draws from the power supply, and an optical output, the laser light that actually reaches the material. A diode turns only part of the electricity into light; the rest becomes heat. Optical output is usually a quarter to a half of the electrical figure, so a module advertised as "40W" may emit 10W of laser light.
Some brands name their machines by optical output, others by electrical power, and some by the sum of several diodes. Manufacturers themselves have written about the confusion: the headline number on the box is not always the number that cuts.
Why it matters
Cutting depth and engraving speed depend on optical output (and on how tightly the beam is focused). As a rough guide, a 10W optical diode laser cuts 5 to 8 mm plywood with air assist in one or a few passes; a 20W optical laser cuts the same faster or goes deeper. Engraving needs far less: a 5W optical laser engraves wood, leather and coated metal well.
CO2 and fiber lasers
CO2 laser tubes and fiber lasers are rated by their optical output. A 40W CO2 laser is therefore much more powerful than a diode machine sold as "40W", and it also cuts clear acrylic, which blue diode light passes through.
How to compare machines fairly
- Look for the optical output in the specification, sometimes given in milliwatts (10,000 mW = 10W).
- Compare the brand's stated cutting results on the same material and thickness, such as 10 mm basswood or 5 mm acrylic.
- Check the wavelength: 450–455 nm blue diodes for wood and leather, 1064 nm infrared for metal, 10,600 nm CO2 for acrylic and glass.
In our laser engraver database each model shows its rated power and, where the brand states it, its optical output separately (62 ranges state an optical figure).
Questions
Is a 40W diode laser really 40 watts?
Often not. Many diode engravers are advertised by the electrical power the laser module draws; the light it emits, the optical output, is usually a quarter to a half of that. Check the specification for the optical output, sometimes given in milliwatts.
How much laser power do I need to cut wood?
As a rough guide, a 10W optical diode laser cuts 5 to 8 mm plywood in one or a few passes with air assist, and a 20W optical laser cuts thicker wood faster. CO2 lasers of 40W and more cut thicker wood and acrylic.
Is CO2 laser power stated the same way?
CO2 laser tubes are rated by their optical output, so a 40W CO2 laser and a '40W' diode laser are not comparable: the CO2 laser is far more powerful.