Or you can calculate that using what's available thru the instruments of the car.
What I did is write down the percentage and miles available before I start trickle charge overnight, which is 1,4 kWh as reported by the car on 120V 15A standard plug using the stock evse on 2018.
Assuming the battery is 40kWh at 100% you can figure out how much it went in at the end of your charging session. For me this is 10 hours(10pm - 8am) , which translates to roughly 30% gain in available charge/ range.
40kWh*0.3 =12 kWh(~45 miles) added in 10 hours and 10*1.4kWh = 14kWh. So used 14kWh to gain 12kWh in the battery, which translates to 85,71 % efficiency.
You might get lower efficiency if you charge on L2 (~7kWh) or QC due to more heat build up in the battery.
Will have to check this once I install L2 at home or record some of the L2 or QC public charging sessions to see what the efficiency would be.
The problem would be the QC since it's not a constant kWh rate and it fluctuates or rather tapers of to prevent overheating of the battery.
If you care about estimated cost of ownership you can download this app:
not perfect but I can track my speed/distance and travel times and see how much it would cost me between my virtual cars.
They're still in beta and not sure if available at your Region.