You need both an adequate power source and adequate wiring. Since voltages are in the teens, wire sizes need to be uprated from code ampacities. Following boat and RV 12V "best practices" is advised. I will be using 3 x 180W Powerhouse units on my 28x15/20 layout (dual-track main), with a vintage Lionel KW as a switched alternate for the few conventional locos I have. I don't have any MTH PS2 or PS3 locos, so no TIU considerations ... yet.