For temporary use only, I have had no problem using the car's "power outlet" for running a CB radio since they draw relatively little power, even when transmitting. The power outlets in both of our cars are rated for "180 watts" or approximately 15 amps. With VHF/UHF ham rigs I have also had no problem with running up to 25 watts. However, I do not operate any higher power this way for all the reasons mentioned previously. The Kenwood TM-281A that I use in my wife's car for road trips draws only about 6-7 amps when operated at its 25 watt low power setting. This is still conservative enough to leave plenty of excess headroom on the car's 15 amp circuit. Always be sure to use a high quality, properly rated and fused plug. In my road trip experience over the years, I have found a 2M radio running 25 watts to a roof mounted 1/4 wave mag-mount will provide perfectly acceptable simplex and repeater range.
When installing a radio permanently which I have done with my car, I agree wholeheartedly with connecting it directly to the car's battery exactly as mentioned earlier.
When installing a radio permanently which I have done with my car, I agree wholeheartedly with connecting it directly to the car's battery exactly as mentioned earlier.