More advanced EVSEs are capable of adjusting the power delivered based on the power available. It does require a sensor on the supply cables to determine how much power is being used, but it's technically capable without a service upgrade. Also, electric companies will frequently upgrade an old 50/100 amp service to 200 amp for low or no cost (because they figure you'll pay off the cost of doing so through more power usage). The panel side of the service upgrade will cost you, but then you'll be able use the toaster oven at the same time as the A/C.