I've never plugged my Sienna in, but I usually keep the truck plugged in all the time since that darned old Texas 350 doesn't like to start when it's colder than 150 degrees. But I save electricity by having a temp cord on the line. The utility company sold those years ago for small change ... to cut down on electricity use. The temp cord has a temp sensor and will turn off the current when the water temp goes high enough (you ziptie it to the rad hose)