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Portable Generators and Power Loss at Altitude in Denver, Colorado

Using generators at altitude in Denver Colorado
Lighting Diagram by Tyler Kaschke, Denver Colorado Gaffer

We often rely on portable generators to power our sets. But did you know they’re significantly less efficient at higher altitude?

You can count on a 2 - 3.5% drop in output for every 1,000 ft of elevation gain. At sea level, your Honda 7000 generator is rated for 5500 running watts. Here in Denver, Colorado (altitude of about 5,200 ft) that same generator will only operate at 85% of its rated output (5.2 x .03 = 15.6% or 4,642 watts).

If you shoot in the mountains, that problem only gets worse! Leadville, CO sits at nearly 10,200 ft above sea level, which means generators will run at 70% of their rated capacity. Your Honda 7000 will no longer be able to power an Arri M40 at that altitude, since it will only pump out 3,850 watts.

Oxygen in our atmosphere drops at higher altitudes. And generators behave similarly to people when it’s harder to breathe. Oxygen also acts as a heat dissipator, so overheating is more prevalent at elevation. For every 10º F above 75º, the generator drops another 1-2%. What fun!

Most manufacturers offer high altitude kits to compensate for the loss in efficiency. The process is called “rejetting” and basically changes the fuel injection rate of the carburetor so the fuel to air ratio is sufficient for elevation. This doesn’t completely solve the problem of power loss, but will make for safer operation. The only real solution is to use a bigger generator.

This setup was pretty simple. One 1200D through red gel and a wall of haze inside the barn with a second one bouncing into the white grip van for some value on the outside wall and ground. When it’s really windy white vans make for a great bounce :)

Many thanks to our wonderful Denver production team and lighting crew who made this commercial possible!

Director @micahjdudash

Producer @meems_mk

2AC Mike Scheuer

Wardrobe @nikkirmalloy

Tyler Kaschke is a gaffer / chief lighting technician with 2 ton G&E grip truck and sprinter van rentals serving Denver, Boulder, Golden, Fort Collins, Colorado Springs, and the Rocky Mountain Region at large.

For more information about grip and lighting tips and shooting video production commercials in Colorado, follow me on Instagram @colorado_gaffer 


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