I plug it in about 8 hours before departure below 30 degrees. No need to leave it on any longer than that unless you really wish to send the electric company about $.25-.40 an hour. Over a weekend that could be more than $10-15.
Your APU is far more expensive than 120v power at the house. After you take into consideration the purchase, fuel, and maintenance costs. I have to use my APU also, anything beats a cold start. All in the cost of trucking.
3 things. One, after a few minutes if you know where the element is located you can hear the coolant "boiling". 2nd. When I plug it in, I will unplug it again, if it is working it will usually spark a little at the plug. 3rd. The extension cord near any connection usually is a little warmer than the surrounding air, or if it is in the snow, it gets warms and sometimes melts the surrounding snow. They pull 1500-1800 watts, which is a fair amount of power. One major thing to remember. NEVER start the truck when it is plugged in. You risk burning out the element because the moving coolant is not in full contact with the element and will burn it out quickly.
Can you explain how you calculated the cost? I think the math is wrong. NVM I see you used 1500-1800w I figured it is 600-1000w.
I can’t plug mine in where I park. If it’s gonna be cold cold night like sub temps, I run it on high idle. Now just for pure comfort, I run my bunk heater even when I’m not in it. Warm truck is very nice to get into when it’s cold.
