With a NEMA 14-50 plug supplied mobile charger will do 32A (240V) so 8kW - which appears to charge about 47km/h according to my 3. (47km is about 29mi/hr) This I actually have tested.
As a very rough rule of thumb, you can use this 1kW (Volts x amps) charges about 3.6mi per hour.
Also, a circuit designed for X Amps should only (by code) use 80% of rated current for continuous draw. A 50Amp circuit is meant to allow a peak of 50 but a continuous draw of 40Amps. (Which is what my Gen2 charger is set to on a 50A breaker). If you look on plugshare.com, for many of the Level2 chargers users will tell you about how many kW they provided for various types of cars - J1772 usually provides 7kW to 12kW depending on the installation.
So a 30A plug (240V) in an RV park should draw 24A continuous, 240x24 is slightly less than 6kW so maybe 21Mi/hr. A guess. 120V - half this.
Allegedly the normal North American wall plug 110V/15A will get you about 5km/3mi per hour. I've never tested this but I have read others who claim this.
Charging with 120V or 240V AC current (as opposed to 450V DC supercharger or ChaDEMO) a Model 3 can only charge at maximum 40A for LR and 32A for SR based on internal circuitry, from what I've read. Mobile chargers are limited to 32A.
I think the plug adapter for the mobile charger tells the mobile what amperage to allow so as not to pop the breaker. If you are trying this, be sure you know where the breaker panel is should you need to reset. Each wall plug type was usually designed for a specific circuit rating and the adapters are designed to limit to this spec. (I.e. your charger won't ever try to get 32A out of a regular wall socket - they are designed for 15A peak)
Note there's a bit of time while the battery will warm up, since charging (I have read) will not happen if the battery is too cold. So trying to charge in the outdoors in really cold weather with 110V may not even do anything since most of the power will go to heating.
FYI: I used the following from Amazon: General Electric WX09X10037 4-Feet 50-Amp 4 Wire Range Cord https://www.amazon.ca/gp/product/B00LQDFOMY
I used this so my Gen2 charger could use the same plug as I had been using for my mobile charger - which gives me options. It wasn't too difficult to wire the charger to the power cord to use a Nema 14-50 plug. Plus, I didn't have to call an electrician to attach my charger, and I keep the wall socket. Just be sure all connections are FIRMLY screwed down. (Neutral capped off in Gen 2 charger, not used)
Also, Gen2 charger with 40A setting, 240V charges about 57km/h or about 36mi/hr
So my calc says 240V/20A circuit will do 16A continuous. This should add about 14 or 15 miles each hour. This is not horrible if you charge whenever at home, unless you have a really long commute. After all, it will stop charging when done so no big deal. I always charge to 80% but some people charge to 90%.
(I schedule for 1AM because I rarely need more than 2 to 4 hours charging. Plus, I draw 40A on a 100A total panel feed for the house, so to avoid conflicting with dryer, cooking, etc. and possibly popping the main breaker (I know, unlikely) I charge overnight. For you, I doubt an extra 16A anytime will be a problem along with other household use unless you have a lot less than 100A main feed.)
It's a whole different driving mindset to start each day with a "full tank".