We have a Runtal Solea STRE 3420 that is 33.8" x 19.7" x 5.5" in our masterbath.

We've found it to be smaller than ideal for the three towels that have been hanging on it since we started renovating our son's bathroom and he's been sharing with us. Towel warmers only warm the area of the towel that is in direct or near-direct contact. They aren't effective in warming multiple layers of a folded towel. We don't use the warmer every day (partly because we haven't hooked up the timer yet) but, when it's going to be used, we rearrange the towels so that the person's towel is fully on the warmer as they shower.

We've decided to put the 3420 in our son's/guest bath and replace it with a STRE 5420 that is 53.3" tall. That should maximize contact area, especially when we are down to using it for just two towels at a time.

We have one that's a "stand alone" piece and actualy plugs in, rather than being hardwired. My wife and I bought it at a yard sale last summer, still new in a sealed box. It gets used as a towel bar now.