SAE, Marine, and NEC all have minimum size wire requirements and I have showed you the proof and you still deny it.
For a 20 Amp Circuit, both SAE and Marinerequire a minimum 14 AWG, and NEC require 12 AWG. Look it up again with my 3 links above. The reason SAE and Marine allow a smaller wire is because they use a 105 degree cable insulation. and NEC uses 60, 75, and 90 degree insulation. Marine goes one step further with a PERFORMANCE Spec of 10 and 3% voltage drop limits. NEC and SAE does not do that. Guess what? When you work with low voltage DC you had better be using a performance based spec because it exceeds minimum safety requirements. With low voltage you had better be limiting losses to 3% or less. Otherwise you are a foolbar HACK.
So to make life easy on DIY I posted a foolbar proof table from Marine standards that can used because it meets the objective 3% Voltage drop which aligns perfectly with low voltage solar applications. Takes all the worry out of cable insulation types. It aligns perfectly with my own Cheat Sheets and does not require anyone to go to some on-line calculator that requires you to enter a lot of variables they may not understand and get wrong. The table is foolbar proof and even you can use it if you pulled your heard out. A 20 amp circuit in your home can go to unlimited amount of receptacles, plug enough toys in and the breaker will trip. The breaker is there to protect the line that is connected to the breaker and nothing else downstream. They are not there to protect line cords, equipment, or to prevent electrocution.
I have proved you wrong with facts jack. You want to go off on a rant that your clock radio, wife's favorite toy, and your toaster oven is connected to a 20 amp circuit uses 16 or 18 gauge wire just proves you are ignorant and do not know the difference between a Supply Circuit and a Power Cord. In your mind they are both the same when in fact they are not.
If you have not noticed but folks like you that give unsafe advice get banned real fast. So keep it up and you will find yourself on the outside looking in. You are no pro or even in the trade. If you were you would know better.
Only you got right in this thread is the meter does not require a 20 amp circuit. It is just asking for trouble, but if you are going to use a 20 amp breaker then you must use either a 14 AWG with 105 degree insulation, otherwise 12 AWG. You stepped in a pile of poop. You did that and asked for what you got, not me. I suggest you shut up and let it go.