I also live in NC (Charlotte), and I can tell you that if the water situation in the triangle area is anything like it is here, you might as well buy the whole gallon. They are talking about us remaining on restrictions through the spring.
Here, at stage 1 (there are 4 total stages), they restrict residential car washing. So, even if they back down on the restrictions, residential car washing is going to be banned until the restrictions are totally lifted, which could be at least another 6 months.
Not to mention, you can mix the ONR to QD strength in a spray bottle, and use it for QDing and as a
clay lube, plus even after the restrictions are lifted, you may want to keep some on hand to use for winter washes in the future....you can wash your car in your garage with a heater going, and don't have to fool with a frozen hose in the middle of January!!!