You can buy heated water hoses commercially but they are very expensive. I simply make my own. But I'm also either very cheap or very frugal, depending on your point of view.
How I make my own Insulated Heated Water Hose and Reflectix Pipe Stand Bag:
To start with, you need a shortish hose. You don't need excess hose laying out in the cold. I have found that a 12 ft long hose suits me pretty much all the time. The potable rated water hose I have is a garden hose (yes, some are listed as safe for drinking water) that was 75 ft long. I found mine at Sam's Club one spring but you can usually get them online year round from Amazon of Home Depot/Lowes type places. It was too long but that's what hose menders were made for. The thicker wall of a garden hose holds up to the heat tape much better than the crappy thin walled RV portable water hoses. I have melted several RV hoses.
I cut off a 12 ft long section of water hose and added a plastic hose mender end (secured with metal worm screw hose clamps) to the cut end. This also got a plastic water hose quick connect on both ends. I screw a quick connector onto any hose bib I need to hook up to and then hook the hose up to it. It's easier and faster to do it that way.
Stretch the hose out straight on a clean surface. Lay a Pipe Heat Cable next to the hose. I seem to use the Frost King Brand a lot. Easy Heat is another brand. You want 18" or more extra hanging out on both ends. Attach the Pipe Heat Cable to the hose, securing it to the hose every so often with electrical tape or a good exterior duct tape. Don't tape it tightly. This is just to hold the cable in place. Do not spiral wrap the Pipe Heat Cable. You want it in a straight-ish line.
Next you need long tubes of foam pipe insulation. Don't use the fiberglass insulation they sell for wrapping the pipes on water heaters. Once fiberglass get wet, it is worthless for insulation and it takes a very long time to dry out. The longest lasting, and most expensive, is neoprene foam. It's great, it's more flexible which is a plus if you will be rolling and unrolling the hose up. Once you over wrap with the Gorilla Tape, you lose a great deal of flexibility. I use the cheaper poly stuff because I tend to stay in one place long term. The inside diameter pipe insulation needs to be the next size up from the outside diameter of the water hose. The Pipe Heat Cable adds about 1/2" to the diameter. I use the kind with the slit down the side. Forget about the "self sealing" aspect. It won't last. I then wrap the whole thing with Gorilla brand duct tape. COMPLETELY! This really takes two people to do well. One to handle the hose and one to wrap the tape around it and make it as smooth as possible, with a good overlap on the tape. This keeps the spiders and other bugs from making a winter home in the nice warm hose. It also makes the insulation last much longer.
Which end do you put the plug on? That depends. I built my bus conversion and I placed an electric hook up inside the water bay for the purpose of plugging heat cables in. So I put the plug on that end. If I had to plug it into the power pole, I would have put the plug on the hose bibb end. BUT I also use threaded quick connections for the hose. I can just swap the ends to whichever end I need the plug on the hose to go.
Since the pipe heat tape is based on temperature, it only turns on when it's needed. I leave the thermo disk on the plug end of the heat tape exposed to the ambient air. It seems to work better for me.
I made a "bag" out of Reflectix (sealed up with Gorilla tape) that was large enough to fit over the pipe stand and reach down to the ground. I "tied it on" with a Velcro wrapper or bungie cord.
The excess 18" or so of heat tape on each end gets wrapped around the hose bibb and hose connection, then the Reflectix bag is placed over the pipe stand and wrapped at the bottom to hold it on. You don't want the wind to blow it off.
My insulated hoses usually last me 3 to 5 years before I have to rebuild with new insulation and Gorilla Tape. I keep the same hose and heat tape. The insulation also protects the hose from the weather. I also never have hot water from it baking in the summer heat.
My current hose was bought in the spring of 2011. I use it 24/7