2016 Tesla Model X: Using an EKM Meter to Track Power Consumption
by Dan Edmunds, Director of Vehicle Testing on May 25, 2016
Electric cars are fundamentally different from gasoline ones on many levels, and fuel consumption tracking is no exception. Like many electric cars, our 2016 Tesla Model X has a set of dash readouts that summarize electricity consumption. They display the consumption rate in Watt-hours per mile (Wh/mile) and total usage for a given "tank" in kilowatt-hours (kWh).
Confused? The first is akin to mpg and the second is like gallons.
But there is a bigger problem. Both numbers are drawn from the point of view of the battery. That doesn't tell the entire story for electric cars because of something called charging losses. Imagine pumping 12 gallons at a filling station and spilling two of them on the ground in the process. The car only knows about the 10 gallons that made it into the tank, but your wallet knows about all 12 of them.
This is no clumsy accident when it comes to electric cars. It's another type of routine consumption that stems from the resistance in the long charging cord and the needs of the on-board battery temperature control systems that operate during the charging process. The only way to account for everything the car is using, charging losses and all, is to look at the meter on the pump. But many EV charge stations, including our Tesla HPWC (High Power Wall Connector), do not have the sort of meter found on every gas pump on the planet.
So we added one.
This meter dates back to the midpoint of our long-term Tesla Model S's tenure with us, but I never talked about it much back then.
We chose a product from EKM Metering because it was a simple, inexpensive and effective meter we could add on easily. We chose a model we could mount on the wall where our staffers could write down the kilowatt-hour reading in the logbook, just as they would record gallons at a gas pump.
It's a revenue grade-meter that lets us track total consumption, which means it doesn't have a reset button. It's more like an odometer than a trip odometer, so we record the necessary kWh figure at the plug-in and plug-out points of each charge and look at the difference. EKM sells more sophisticated meters that automatically transmit data to the cloud, but our HPWC installation is buried in an underground parking structure.
With a little help from an Excel spreadsheet this setup will allow us to track the true consumption of our Model X. Tesla's in-car meter is great for driving style feedback, but our EKM meter is where the money part of the story lives and breathes.
Dan Edmunds, Director of Vehicle Testing @ 1,997 miles