Review on 🔌 Zerostart 2600900 Portable Electric Car Heater - Interior Compact Plug-in Warmer, 3,000 BTU, 120V, 900W by Sean Powers

This heater puts out a pretty decent amount of heat. It's quite heavy and a little bulky, so you'll need to carefully consider where to mount it. There is little support for the mounting plate, so you'll need to reinforce the base of the device to keep it from rattling. The power cord that came with the unit is most likely too short for smaller vehicles (if you have a plug installed in the front of the vehicle). I don't have a long history with this device, but so far it works as advertised.