My original plan was to only use the car in the summer months so I didn't need to build any heat systems into my plan, however, its so much fun to drive that I changed my mind and am now adding heat after the fact. I plumbed in two 1500W Kats heaters in series. I also wired them in series and am running them off the main battery pack. Because the heater coils draw 3.5kW-4kW when running, I decided to wire them to a switch in the cabin so I can control when it is on and off. To make it look good on the dashboard, I purchased a used window-defrost button so that it can fit nicely into the Porsche console with all the other buttons. The switch also has an LED to let me know when its activated. Below are two pictures. One of the switch in the cabin, and the other is a view of the tank heaters under the car.