I boarded at a farm in Hudson, OH that charged $350/month, which had one in the wash rack. It was wired and hung next to the lighting fixture. It was really nice to have in the Winter when I had to hold my horse for the farrier. You could wash your horse in the Spring for an early show and keep it warm while it was drying. Nice!
They had it on a timer system like you find in heated bathrooms.
My barn has heated lamps in the wash stall that are hung above the horses longways, nose to tail. I love it, but one of my horses HATES it. He is 17.2, so not sure if it is because his back is closer the to heat source, but every time it is on he squishes himself to the side of the stall to avoid it. He normally gets chilled easily, but just can't stand the heat lamp. He's generally my most stoic horse but the heat lamp drives him nuts until he is dancing in the cross ties, switching from side to side. I've checked many times by holding my hands above his back and it never seems too hot. Other horses seem to like it, but just a friendly heads up that heaters are not appreciated by all horses!
I like the timer for safety, but our timer will not turn off once it is on before the time is up. That means if someone turns it on and then I have to bring in the horse that doesn't like the heater, I either have to use the other wash stall or wait until the heater turns itself off. If you can, I recommend setting it up with a timer that also has an off switch.
We have one, but it's an old one that is really just a PAR lamp,of some sort. Gives off a bit of heat but not enough to skip the post bath blanket. I think the ones that are the linear radiant lamps work better since they heat the horse not the air.
We got ours at an auction. Came from a (human) spa that was going out of business. I think they used it above some kind of hydrotherapy table. At any rate, it works well and in conjunction with warm water makes bathing hairy horses in sub-50 degree weather bearable for all concerned. I didn't want propane in the barn so we had to look for a while to find one that was electric. Here are some similar: http://www.farmtek.com/farm/supplies...oductId=168307