Thanks to gedabrcaer for this Frugal Baby Tip!
I have my changing table right next to the bathroom sink, we just use cold water on a very thin washcloth then I squeeze it in my hand for a little while to warm it. My son never seemed to mind. Maybe he just has a tough little butt. So many people use the disposable wipes cold, I really don't think that most babies mind the cold water. But I have heard that some people use a wipe warmer with premade wipe solution with tea tree oil added, to control bacteria. But I would think that is just as wasteful as running the water since the electricity would be running all the time.