I have a free heating unit (plug-in for ordinary outlets, very clean) to give away for free. The original unit must have cost around $60 or a bit less. There are two dials, one with 3 stages and one sliding scale, both for temperature adjustment. The first dial is broken (it's stuck at one of the stages), but the other dial has been perfect for me to adjust the temperature throughout winters and summers every night at Stanford, so aside from that it's fully usable and has a wide range of heating temperatures. I'm moving off-campus soon, so that's the only reason for giving it away.