Our home has a 200 Amp (240 volt) main panel. We recently installed a new HVAC system, and as part of the research I calculated the potential loads for the HVAC system plus a possible Level 2 charger for my (on order) Tucson Plug-in Hybrid and a possible upgraded pool heater. Using the National Electrical Code (NEC) calculations, it appeared that we might exceed 200 Amps at times and, as a result, would have to upgrade our service from the street to 400 Amps. Depending on the (unknown) size of the buried service cables, this could cost many thousands of dollars. Even if the service cables were large enough, we were probably looking at hundreds of dollars for the panel upgrade.
I installed a Sense energy monitor system in the main panel ($300). So far the highest draw I have seen is 67 Amps. I can easily add a Level 2 charger (and upgraded pool heater) without having to worry about upgrading our service. The Sense energy monitor paid for itself in terms of cost avoidance and peace of mind.
sense.com
If you are not comfortable working in an electrical panel, even with the main breaker turned off, PLEASE call an electrician to do the installation of the Sense energy monitor.
Note - Tripping the main breaker due to an overload (i.e. after adding a Level 2 charger) is considered a nuisance and not a safety issue. There is the option of installing the charger, seeing what happens and upgrading the service if necessary.
All this said, I am going to start out just using 120-volt charging to see if that is sufficient. My wife's son-in-law commutes using a BEV and does fine with 120-volt charging. I'm retired, and there's this thing called a pandemic, so I really don't drive that much any more.