T07573 is Costco model number, T07571 is the retail model number. Though NG has less output than Propane or Gasoline; NG is much more convenient and unlimited. No need to run out to refill propane tanks or gasoline cans. No need to worry about gas gumming up the carb. NG is always available except for extreme mother nature's disasters ie earth quake.

A lot of people have trouble getting NG to start on their generators. Much has to do with understanding how the choke works with your generator when using natural gas. Some experimentation needed to get the feel. First time I used NG, I had a hard time getting the generator to run until I realized: use the choke to purge the air and then back off the choke to get the generator running. Unlike gasoline, do not need the choke for running.

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