Mine was factory installed in my '17 Cascadia. It is 1800W. Most of the shops will install them if you don't have one, usually a larger one than mine.
I've had my truck around 6 months, so it was a little before that. Some people have said that it is because of all the drivers that need CPAP machines, others have said it is because Swift wanted to give us the option to use electrical appliances instead of more dangerous fuel burning stoves that many used.