When you're plugged in. Temperature was 34* outside, 39* in the van. Hot plate on (medium) and on the floor, it raised the temps to 51*. And it boiled a kettle of water in only a few minutes, and you can keep cooking whatever since it's always on for heat. Very small and compact. All settings registered at 742 watts.
Mine was from HorrorFreight ($12 on sale), but looks just like this one:
https://www.amazon.com/Gracelove-Po...TF8&qid=1489679943&sr=1-10&keywords=HOT+PLATE
Mine was from HorrorFreight ($12 on sale), but looks just like this one:
https://www.amazon.com/Gracelove-Po...TF8&qid=1489679943&sr=1-10&keywords=HOT+PLATE