Well, I've been driving my Model 3 for almost a year now. Here are the stats:
Configuration: LR RWD, 18" Aeros, Tire Inflation 42-45 lbs
Location: Baltimore, MD area
Overall Average Wh/Mile: 237
Average Wh/Mile (May-Oct): 221
Average Wh/Mile (Oct-Apr): 254
Mix of highway and local roads. Ran mostly in Chill Mode.
Took 6,600 miles of trips that included 45 Supercharger stops which costs a grand total of $211.16. Note that 8 of those stops were zero cost because Tesla was not charging for Supercharger use in NC and SC for a period of time following one of the hurricanes. So the actual cost would have been about $40 higher.
Purchasing the Model 3 qualified me for an EV Rate Plan from my electric utility. This is a time of use plan where you pay more during peak hours but less off peak. The car was charged during off peak hours and I did some minor load shifting of electric use (laundry, dish washer) to off peak times. My annual electric cost for the past 12 months was $255 more than the previous 12 months. Given that annual electricity costs vary based on average temperature, I compared my last 12 months of electricity usage with the average annual cost over the previous three years. This showed that my annual electricity costs for the past 12 months was actually $122 less than the average cost over the previous 3 years. This is due primarily to nighttime electricity cost savings (due to the EV Rate Plan) for heating the house during the winter months. This virtually offsets the cost of charging the car!
As for Model 3 maintenance costs, I spent a total of $160 for tire rotations.
For me, so far, the operational costs of this car are ridiculously low.