rmay635703 wrote:Look at your panel, add the amps up of populated breakers.
If you have 120 amps or less of installed load in the panel
good to go.
It's not anywhere near that simple. The following might be typical: the above procedure gives you 400 amps. The NEC load calculation gives you 200 amps. And actually measuring the current on your service conductors gives you under 100 amps.
To answer the question properly you need to do an NEC load calculation. The EVSEs will show up in the calculation as 125% of the EVSE's pilot signal with no demand factors. So if the existing load calculation is under 125A, then you could add two 30A EVSEs to get a total under 200A. I don't have any rules of thumb for doing an NEC load calculation.
Now as a practical matter, even if the NEC load calculation before EVSEs is 200A, the actual peak current on the service conductors might be only 100A. The EVSEs are basically the only household load that will actually add their rated current to that figure on a continuous basis. So you could add two 30A EVSEs to the service while keeping the service conductor current under 160A continuous (the maximum allowed for a 200A service).
Also, it is important to notify your power company that you're getting an electric vehicle. That 200A service might have service conductors on the power company side that are really only good for 100A continuous, likewise for the transformer feeding your service. If you are regularly adding a full 60A continuous load to your service, the power company may need to upgrade their equipment.