I just installed a fancy ammeter and can now monitor the electrical use of my inexpensive Chinese parking heater. The glow plug draws 7-10 amps on startup, just like my almost identical Espar unit. But it also comes on for about 20 seconds during shut down. The fuel is shut off, the glow plug turns on, and the fan blows fast, then slowly through the cool down cycle. I'm sure that the idea is to make sure that there is no carbon build up. I run the Espar on its own tank of Klean Heat because of problems I've read about. The parking heater uses from my diesel tank.
I got the Espar for $600 on a great sale. I got the Chinese parking heater for $130. The Espar has a simple thermostat with no numbers or indicator light. The Chinese heater has a nice little gauge that shows when the fan is running, when the fuel pump is running, when the glow plug is on, the temp in C or F, and it can be set to run for a certain time or come on and off at certain times. Plus a remote that allows me to control it from bed. What a difference a decade makes.