Why Electric Cars Aren't Yet Great for Towing

0 0 Editorial Team December 9, 2019 Edit this post

By Chris Perkins, Road & Track

They can pull, but they can't do it for long.

A long-range Tesla Model X can tow up to 5000 pounds, and the automaker claims over 7500 pounds of towing capacity for its upcoming Cybertruck. Respectable numbers, but here's the thing—today's electric cars, regardless of make, just aren't great for towing.

As Engineering Explained's Jason Fenske describes in this video, the energy density of electric cars leaves much to be desired. The current state of battery technology is such that only so much energy can be stored in a package that's not too big for a passenger car. The Model X's 100-kWh battery pack has the most energy storage of any production EV. The EPA certified the Model X Long Range as being able to go 328 miles between charges.

When you add a trailer to the mix, that range goes way down. Fenske details a couple of hypothetical trailering scenarios for a Model X in this video. In one, he simulates a family taking their Model X on a camping trip, driving 100 miles up a 1-percent grade at 75 mph. Factoring the 5500-pound weight of the Model X itself, plus 500 lb of payload and 5000 lb of trailer, increased drag coefficient from the trailer, rolling resistance, and gravity, Fenske calculates that 100.4 kWh is needed to make that trip. In other words, you'd need to recharge to make it.

That's not factoring use of HVAC and other ancillary systems either. Fenske calculates that doing the same trip without the trailer would only take around half the energy, and towing the trailer at 60 mph requires 84 kWh of energy. Essentially, a trailer can kill EV driving range.

For comparison, he runs the same 75-mph trailering uphill scenario with a Ford F-150. That truck comes with a choice of 23- or 36-gallon fuel tanks. Given that a gallon of gas is equivalent to 33 kWh of energy, that means the Ford has around 775 to 1200 kWh of energy capacity. The trip would require 170 kWh of energy, so the 23-gallon F-150 would only need to operate at around 21 percent efficiency to do it, while the 36-gallon truck only needs to work at around 14 percent.

Fenske also runs some numbers on the Tesla Cybertruck based on preliminary specs, and calculates how the Model X trip would go with no incline and going downhill. The numbers are a lot better, but still a ways off the F-150 going uphill.

So while you can tow with an EV, they won't be practical tow vehicles until their energy capacity increases significantly. When the Model X offers a 200- or 300-kWh battery pack, towing long distances will be much more practical.