[Isaac Zachary]

I prefer the circulating tank heaters. The more powerful, the better, if you don't mind plugging it in an hour or two before you need to go.

If you have a 20A outlet, I'd go for a 2,000W heater. If you only have a 15A outlet then you can't go any higher than 1,500W. But if you plan on leaving it plugged in all night then you'd probably want to go with whatever a stock block heater would put out. For a Silverado, I'm guessing an all night block heater would be around 500 to 750W.

If you go with a high powered circulating tank heater, the Kat's brand (which is usually rebranded as the store brand in any parts store) don't have a one way valve, which could limit cabin heating as some coolant will bypass the heater core as you drive, but your mileage may vary. If you don't get temps well below zero Fahrenheit you're probably fine with a Kat's. However, i understand the Zerostart circulating tank heaters have a valve, but are more expensive.