OK, hopefully there is still time before the OP actually orders a "Heated Hose"....
Here is my 2cents worth from 5 years of full time living in an RV.
DO NOT BY A PIRIT ...or any other heated hose based on thermostat in the mix.
Here is what we have used in our rig since the _old style_ Pirit brand hose nearly cost us having to install new pluming in our big rig (i.e. thermostat failed and lines nearly froze).
This is the best hose IMO and there is no thermostat. You know it is working because it is warm to the touch. Plug it in, it works.
Here is what I recommend:
Camco 22904 hose
PS... OK, so why do we have one here on the mild-weathered Oregon Coast? Because we've learned that all it takes in a typical RV park is for temps to hover around freezing for any amount of time and the feed line from park to rig is likely to freeze. Back in a stick and mortar home you could just leave a sink on drip mode. But in a rig you will chance freezing the water in your grey tank or the line to the park's sewer. I've seen both and these are expensive repairs...just ask my neighbors who still don't believe it _freezes_ on the Oregon Coast.
Last night temps were mid 20's as recorded at our rig's weather station.
They work amazingly well.