EV Road Trip Comparison: 2015 Tesla Model S vs. 2015 Chevy Volt

Tesla and Volt at Supercharger
The Volt waits while the Tesla charges.
Image source: Karl Bloss
In mid-August our 2015 Chevy Volt discussed in last month's essay on plug-in hybrids displayed an "Engine Maintenance" warning.   The message (see below) informs the driver that the car has used so little gasoline that it needs to burn some, presumably to keep the fluids in the internal combustion engine (ICE) moving, seals lubricated, etc.  From June through mid-August, the car was driven about 1,500 miles of local-only trips fueled primarily by electricity and only 0.4 gallons of gas.  

The on-screen message startled my daughter who was still getting used to the car.  After some time on Volt forums, I learned that this message is sort of a badge of honor among Volt drivers because it means you're using so little gas.

Low gasoline usage maintenance screen
Image source: Karl Bloss

Time to Burn Some Gas

The end of university summer vacation necessitated a return trip to Kansas City.  In the past, we have either made the drive from Michigan with a rented minivan or with the 2015 Tesla Model S depending on the amount of stuff to be transported.  This year, my daughter was taking the new-to-her Volt back to school, but we parents also needed to tag along in the Tesla to transport more stuff as well as help with the move-in process.  

With two vehicles driving the same route under the same conditions, this presented a perfect opportunity to do some side-by-side testing.  

Tesla US Supercharger Locations
Image source: www.supercharge.info

BEV vs. PHEV

Those of us driving electrified vehicles, both battery electric vehicles (BEVs) and plug-in hybrid vehicles (PHEVs), know that driving electric around town is easy.  Wake up to a full "tank" of electrons every morning.  Run your errands during the day, no need to stop by the gas station.  Plug it in and the cycle repeats.  

Road trips are where we really experience the functional difference of BEVs versus PHEVs.  BEVs need fast charging to make road trips practical.  PHEVs just need a gas station to keep their onboard generator running once the battery is depleted.  If you are unfamiliar with how that works, please see last month's essay on PHEVs.

Tesla vs. Other BEVs

Tesla is still the king of BEV road trips.  Yes, Electrify America and other networks are making great strides, but with fast charging capabilities of 250 KW, nearly ubiquitous coverage of major routes, and the redundancy of multiple charge points at every location, Supercharging is still far superior than any other system.  How would the Tesla stack up to the Volt on a road trip?

EV diversity in our garage: Tesla, Chevy, Nissan, and Zero
Image source: Karl Bloss

2015 Tesla Model S vs. 2015 Chevy Volt 

For sake of simplicity, I am focusing on range and refueling, thereby ignoring other aspects of these two vehicles such as space, comfort, Autopilot (1.0 in the case of the 2015 Model S) and the killer stereo in the Tesla.

Vehicle Basics

The 2015 Tesla Model S P85D had a nominal battery capacity of 85 kWh providing a range of 252 miles when new.  My 2015 model with over 80,000 miles on the odometer has lost about 5% of its capacity due to normal degradation of its lithium ion battery pack, so the range is closer to 239 miles.  Charging power is limited to about 110 KW when the battery is nearly empty and this charge rate quick tapers off as the pack is charged.  At 90% state of charge (SOC), the charge rate often drops to around 20-30 KW.  Therefore, this car really cannot make full use of the newer V3 Superchargers that boast the 250 KW initial charge rate.

The 2015 Chevy Volt has a usable battery capacity of about 11 KW with a range of about 35-40 miles on electric energy.  After that, the ICE kicks in to keep the battery charged fed by a 9.3 gallon fuel tank for an additional range of around 345 miles giving the car an overall highway range of around 380 miles.  

Our route with charging stops on PlugShare route planner.
Image source: Karl Bloss
The Route

Our preferred route from Muskegon, Michigan to Kansas City, Missouri takes us along the Lake Michigan shoreline, south of the Chicagoland area, I-80 west across Iowa turning south at Des Moines, then I-35 towards Kansas City.  The distance is just over 700 miles which, although we've done it once in a single day, we find comfortable to split up into two days.  

Based on our experience with this route, we prefer to break it up near Iowa City.  The Coralville Transit Intermodal Facility (PlugShare location) offers a good selection of hotels all in walking distance to free Level 2 ChargePoint stations.  In case those are blocked by usage or ICE vehicles, the backup charging location is the Coralville Supercharger (PlugShare location).  

Here was the plan (PlugShare links for each stop):

Wait, Why Two Stops?

If you recall the range of my Tesla (239 miles), I should have been able to stop only once to charge even on the 400 leg of the trip.  So why more than one stop?  There are two reasons.

The Range Limitation is not Always Dictated by the Battery

The first is pretty banal: bio-breaks.  239 miles at an ambitious 70 MPH average is over 3 hours of driving.  My body prefers to have some sustenance, caffeine and a pit stop way before then.  

The 20-80% Sweet Spot

Furthermore, EV battery longevity is best when maintaining your SOC in the range range of 20-80%.  For a road trip, charging to 100% before the trip occasionally will not trash your battery, but I try to not do this on a daily basis.  Since the range limitation tends to be the bio-break, I rarely charge beyond 90%.  In addition, above 80% SOC, the DC fast charging rate on EVs drops significantly so as not to "cook" the battery with excessive heat.  Depending on your car's battery management system (BMS), it may take just as long to charge from 80-100% SOC as it does from 20-80%.  

My wife would get nervous when the tank dropped below 1/4 on our gas cars.  Similarly, it's a good idea to keep some reserve range for things like detours and traffic jams.  20% reserve is a good rule of thumb and also helps maintain battery longevity.

The Chevy Volt battery was over-engineered so that only about 11 of the roughly 17 kWh battery capacity on Generation 1 (2011 - 2015 model years) Volts is tapped.  That means from a user perspective, it is generally accepted to charge the battery to 100% and run it to 0% without fear of premature battery degradation.

Day 1: Michigan to Coralville

In battle, the saying goes "no plan survives contact with the enemy."  So it is with road trips.  

First Stop: St. Joseph, MI

With an afternoon departure from home, our first intended stop was the fairly new Michigan City, IN Supercharger, conveniently located at a Meijer grocery store 132 miles from our starting point.  The bio-break issue reared its head in less than two hours, so we opted to stop earlier at the St. Joseph, MI Supercharger (Plugshare).  Since we were stopped, the Panera location there offered good coffee, so the 15-minute layover was a welcome break.  

Tesla: 15-minute charge, free.  I have lifetime free Supercharging based on my purchase date.
Volt: Battery depleted after the first 37 miles, but plenty of range left thanks to the ICE.

Country Club Hills, IL Tesla Supercharger
Image source: Karl Bloss
Second Stop: Country Club Hills, IL

With only 30 miles between St. Joseph and Michigan City, we skipped Michigan City and decided to stop for supper at Country Club Hills, IL (PlugShare) just south of Chicago.   This Supercharger is at a mall with plenty of food choices including a Panda Express we happen to like.  The sit-down dinner took more time to eat than the Tesla needed to charge for the next stop.  Even though charging speed slows at a higher SOC, if that charging time is masked by other travel activities (like eating some yummy Pad Thai), this helps reduce the time of the next charging stop.  

Tesla: 45-minute charge, free.
Volt: Even fully loaded with 255 miles down running the A/C, the Volt was running efficiently.  No need to get gas until the next stop.  

February 2020 report on the Peru, IL Supercharger
Image source: screen grab from Ben Nelson's video
Third Stop: Peru, IL

A stranded semi truck in a construction area forced westbound I-80 traffic to flow at a cold molasses pace through the remaining single lane.  80 miles to the Peru, IL Supercharger (PlugShare) took over two hours and I needed a coffee.  

This location is one of our favorite Hy-Vee grocery store stops that was featured in a video by 300MPG.org's Benjamin Nelson during our February trip to Fully Charged Live Austin.  As the Tesla charged, we picked up some snacks in Hy-Vee as well as hot drinks at the Starbucks stand inside the store.  The Volt gas tank was filled for under $17 at the adjacent gas station.  

Coralville Intermodal Level 2 ChargePoint stations.  
This is picture is from a prior visit with a Gen 2 Volt.
Image source: Karl Bloss

Tesla: 40-minute charge, free.
Volt: 5.741 gallons of premium gas @ $2.899/gallon = $16.64

Day 1 Destination: Coralville, IA

With 400 miles down and a midnight arrival, it was time to recharge ourselves with sleep.  Both Level 2 ChargePoint stations (PlugShare) were available, so both cars were plugged in before we headed into the hotel.

Tesla: Overnight Level 2 charge, free.
Volt: Overnight Level 2 charge, free.


Day 1 Summary 

Tesla: 3 Charging Stops, 100 Charging Minutes, $0 Fuel Cost

Instead of 2 planned stops, we ended up making 3 due to travel convenience.  Based on the range of the Tesla, we could have made a single long charging stop at Country Club Hills with one really long charge.  Fortunately, the Supercharger network is dense enough that there are convenient choices along the route.  

With 6 hours and 15 minutes of driving (plus about 30 minutes of sitting in traffic), 100 minutes of charging is about what I would expect for this vintage Tesla.  That is, about 1 hour of charging for 3 hours of driving.  The newer models that can use the higher power for a longer sustained time will have a significantly better drive to charge ratio.  Then again, my 2015 vintage car gets free Supercharging for life, which is hard to beat.  

The Volt took less than 6 gallons of gas on Day 1.
Image source: Karl Bloss
Volt: 1 Fuel Stop, 5.741 gallons, $16.64, 5 Minutes 

The refueling requirement of less than 6 gallons for 400 miles is pretty fantastic.  More fuel than that was actually used since the Volt used some fuel in the 140 miles between the fueling stop in and the hotel.  Only one 5-minute refueling stop costing less than $17 for the day is extremely practical.  Even with Tesla's industry-leading charging rates, it is hard to beat liquid fuels for energy density delivery speed.  Too bad ICE cars waste 80% of that energy to heat.

Driving the Tesla never gets old for me.
Image source: Karl Bloss

Final Thoughts on Day 1

This was my first road trip with the Volt.  I'm impressed.  As I wrote in the Plug-In Hybrids Need Love Too essay, consider a PHEV as your first electric car.  Particularly with some very affordable used vehicles out there, PHEVs are a great way to start driving electric now without the range anxiety of a BEV.  

I still love driving my Model S though. 


Next Time:  Day 2

Happy EV road tripping and keep charging ahead!


Resources:

If you are in the market for a Tesla Model S, Model X, or Model 3, Tesla has reestablished its referral program.  Feel free to use my referral code to get free Supercharging (at the time of this publishing) for your Tesla:  http://ts.la/karl5062

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