The charge cord included with the clarity will charge at 12A and 120V. The equates to 1.44kW, so 1 hour of charging will use 1.44kWh. Very roughly 90% of that will actually make it into the battery. There is less of a "taper" with L1 charging, but as the battery gets full, charging will slow (the charger is built into the car and controls how much power is drawn).
So a good rule of thumb is 1.44 x $0.13 per hour of charging or about 19 cents per hour. 6 hours of charging would be ~$1.12
Oregon Electric Vehicle Association Vice Chair
NDEW City Captain