2013 Tesla Model S in Florida, during New York to Florida road trip [photo: David Noland]Enlarge Photo
Well, it's now been a year since I took delivery of my dark green 2013 Tesla Model S with the 60-kilowatt-hour battery.
After almost four years of waiting, those first days after delivery were euphoric. As I recall, the words "greatest freaking car in the entire freaking Universe" (or thereabouts) passed my lips on several occasions during the honeymoon period.
But my view has become, shall we say, more nuanced after 365 days and 15,243 miles of of blizzards, bird droppings, heat, cold, glitches, groceries, dogs, road trips, drag races, Superchargers, traffic jams, service visits, vampire draw, software updates, and "Check Tire Pressure Monitoring System" warnings.
First, some numbers.
"Fuel" efficiency and cost
To cover 15,243 miles, I used 5,074 kWh of electricity, for an average of 333 watt-hours per mile. That's a bit better than the car's EPA-rated efficiency of 350 Wh/mi, and converts to precisely 3 miles per kWh.
I used about 1,275 kWh of free Supercharger power on three long road trips totaling about 4,000 miles. So about 3,800 kWh of the 5,074-kWh total came through my electric meter.
2013 Tesla Model S electric sport sedan [photo by owner David Noland]Enlarge Photo
At my local utility's rate of 14 cents/kWh, that works out to a total fuel cost for the year of $530, or about 3.4 cents/mile. Contrast that to about $3,000 and 20 cents/mile for a comparable car like the Mercedes S Class.
But the Model S actually used more electricity than the 5,074 kWh on the car's energy meter.
For one thing, the charging process is only about 85 percent efficient. Which means that for every 85 kWh used by the car, 100 kWh came through my electric meter. In reality, that 5,074-kWh number is actually more like 5,700 kWh.
In addition, my car's "vampire" power draw while parked and shut down averaged about 4.5 kWh per day for the first 10 months, and then about 1 kWh per day after a software update two months ago. I estimate the vampire draw sucked up an additional 1,400 kWh or so.
That brings total actual energy usage for the year: about 7,100 kWh--putting efficiency at about 466 Wh/mile, or about 2.1 miles/kWh.
The vampire and charging losses bumped the year's real fuel cost up to $820, or about 5.3 cents per mile. Which is still barely a quarter of the fuel cost of a comparable gasoline car.
Winter vs summer
As with all electric cars, my efficiency was much lower in cold weather. For the April-to-October period, I averaged 301 Wh/mi, compared to 371 Wh/mi for November to February.
Although I didn't measure month by month, these numbers imply that energy usage in July--the hottest month--was probably in the range of 290 Wh/mi, while January's was close to 400 Wh/mi.
Earlier this winter, during my first January with the car--which was followed by the coldest February in recent history around these parts--I found that my energy usage nearly doubled for the short local trips that I usually take.
Time after time, I'd come home from a run to the grocery store or the chiropractor with an average consumption of well over 500 Wh/mile. (That's before counting vampire and charging losses.)