Model S Equivalent Mile Per Gallon closer to 60 EMPG

I noticed that my model S was "leaking" range every day it sat unplugged so I decided to get a real idea of the effect of this on E-MPG. I also wanted to know exactly what I was paying for the car per mile so i installed a household watt hour meter like the one on the side of the house right before the wires go into the charger. I have tracked the KWH usage by the charger over the past 6 weeks or so and have come up with 351kw took the car 687 miles. This yields an efficiency of 511wh/mile. at 4.00/gallon and .14/kwh this period yielded 56mpg equivalent. which is a lot different than the 89 empg that the epa rated this car at. The car seems to us 3kwh per day just sitting there. Over the 28 day period i checked this that would account for 84 kmh of the 351. if you take that out the efficiency would have been 388wh/mile or 74empg (getting closer). and i am told that chargers are 90% efficient or so? (correct me on this if someone knows the actual on a 220v 40amp plug) So if the charger were 100% efficient and they could find a way to fix the daily leak the car would have done 350wh/mile which is a lot closer to the 325wh/mile the screen claims in the trip log over the same period.

So leaving the computers on is robbing me of 18mpg.

There are two kinds of energy consumption that don't get counted by the kWh counter on the trip meter. First, there is the vampire load when the car is not moving: electronics, battery heating/cooling, etc. Second, there is the energy consumed as a result of charging inefficiencies: the difference between the number of kWh that the car thinks its getting and the number of kWh that your utility is selling (and billing you for).

Like others, I love the car and don't worry about it.

You will be charging in the past? How will that work? I thought only Flux Capacitors could pull that off.


@DouglasR: Sorry, but that's simply not correct. The vampire loads, etc are all accounted for. This has been confirmed multiple times.

You are correct however about the loss due to charging inefficiencies.
I assume it's less than 10% (90+% efficient DC converters are not uncommon). Worth mentioning: Tesla has stated that charging at less than the maximum is less efficient.

@tommy-tesla - Are you saying that the trip meter records the vampire loss while the car is stationary? Because I think that's wrong. Unplug your car and let it sit overnight. Then look at kWh consumption on the trip meter. It will show 0 kWh used since the last charge.

I do believe, however, that the vampire load is accounted for on the trip meter when the car is moving.

@DouglasR try driving the car after it having sat all night. If I'm right, the consumption will jump up. Normally I don't see it because I charge every night. I'm pretty sure I've casually observed it, but I'll make a point to test my claim tonight.

For me, the car's consumption behavior starting out is the same whether it has been sitting all night or just finished charging. Run the heater on a stationary car, and see whether the trim meter records the usage.

My understanding was that the tally isn't updated without the car moving.

When I parked:
Since Last Charge: 46.9 mi 15.3 kWh avg 327 Wh/mi
Rated Range: 176 mi

After ~ 12 hours:
Since Last Charge: 46.9 mi 15.3 kWh avg 327 Wh/mi
Rated Range: 171 rated range

Thus the loss of approximately 5 * 300 = 1500 Wh isn't in the
trip counter

Add 0.2 mi of very slow driving (downhill):
Since Last Charge: 47.1 mi 15.4 kWh avg 326 Wh/mi

So it looks like I was wrong, but I need a bigger vampire drain
to be completely sure.

electron, i dont really care how they calculate mpge on the sticker, but i do care about fuel cost per mile and my calculations are valid, call it something else if you want.

brian h, i drive the same amount but i like it a LOT MORE!

My 60 is consuming 200w per hour keeping the vampire alive, 24 hours per day stationary or moving. $.34/kWhr = $599 per year. Not a large amount of money, but a complete waste. Need to leave a car at the airport while we go on a 3 week vacation. Disappointed we can't take the MS...have been spoiled for 2 years with our LEAF; guess we'll take it to the airport.

Certainly hope someone at TM is working on this.

No taking the long way to work? No running extra errands as an excuse to drive? No Sunday joy rides?

1123.7 miles, 336.4 kWh this works out to 112 eMPG. This is my real world consumption for the last month.

Of course this does not include the electricity used to keep the car in standby mode. It also does not include the electricity to open and close my garage door.

I guess you can calculate the consumption all sorts of different ways.

This car is awesome!! It makes my diesel Jetta seem like a fuel hog.

My consumption is a bit lower at 310 kwh average. (60kwh car)

I don't care what the equivalent eMPG is, I just enjoy driving my car.

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