Mirage #2, The Even Fancier Metro, came with the OEM cartridge style block heater.
I'll have to confirm this, but I think it's a 400 watt unit. (EDIT: confirmed below by klroger - it's 400w.)
I was curious how fast it warmed things up, so plugged it in and checked the coolant temp every 10 minutes (via a ScanGauge).
Elapsed time
(minutes)Coolant temp (F / C) Temp change (F)
from previous0 40 / 4 (ambient, cold soak) 0 10 42 / 6 2 20 49 / 9 7 30 57 / 14 8 40 62 / 17 5 50 67 / 19 5 60 71 / 22 4 70 75 / 24 4 80 78 / 26 3 90 80 / 27 2 100 82 / 28 2 100.5* 100 / 38 18
* That last reading was after starting the engine and letting it idle for 30 seconds. I figured the water jacket / block wouldn't be heated uniformly by the block heater, so circulating the coolant past the temp sensor would be a good idea to get a final reading. (I don't think that 30 seconds of idling actually added 18 degrees F worth of heat to the coolant).
It looks like around the hour-and-a-half mark the amount of heat being added has slowed down a lot. And at some point it's going to reach equilibrium, losing heat as fast as it's added. Though we weren't quite there yet.
Edit... graph!