in cars - its extremely easy - doesnt matter if you are in alaska or in sahara - you have the volumetric capacity printed on the car itself, assemble system, pressure test with nitrogen, verify all leak points, vacuum it out, fill the quantity/weight of gas mentioned on sticker. Let it roll.
Does the market assume that the factory has A/C techs filling new cars with cylinders and HVAC manifold gauges while chewing paan and scratching nads?