Confessions of an EV Owner

By: Hy Murveit

I confess, I had been waiting a long time for an EV when I finally ordered my Nissan Leaf in October 2011. I oversized my roof solar-panel installation in anticipation of an EV in Dec 2006. I unsuccessfully bid on a used Rav4-EV in Nov ‘07. I put down a refundable $5000 deposit on a Tesla Model S in March ‘09. After I picked up my shiny new red Leaf in May 2011, I insisted on using the Leaf to pick up my daughter across the bay at Oakland Airport. Not knowing whether it could have made the standard 81-mile all-highway round trip over the San Mateo Bridge (it could have, but just barely), I arranged to arrive a couple of hours early and charged at a nearby Nissan dealer.

 

Since then we purchased an 85kWh Tesla Model S in Nov ‘12–my wife Leslie and I alternate months with the Leaf and Tesla, and we have learned a lot more about owning and operating all-electric cars (BEVs–the kind without any backup gas engine).

EV Advantages. The two BEV cars have some definite advantages over ICE (internal combustion engine) cars. (1) No gas. Like your cell phone, you plug them in when you get home in the evening, and they’re ready to go in the morning. No stopping at gas stations–ever. Not being able to use gas stations is usually stated as a disadvantage, but for me there’s definitely a savings of time and hassle by plugging in. Also, my employer (Google) generously provides free charging at work making the juggling of charging two EVs a non-issue. (2) Quiet. The electric motors are noticeably quieter than gas engines. Driving is not completely quiet due to wind- and tire-noise, but much more pleasant than much louder ICE cars. (3) Carpool lanes. This is, of course, a public policy perk, but it is nice to take advantage of the carpool lane on crowded Bay Area freeways.  (4) Pickup. The Model S is a very fast car. My car is spec’d at 0-60 in 5.4 seconds, and the performance version reaches 60 mph in 4.2 seconds. The Leaf is not a fast car at highway speeds, it seems average, but does have very noticeable pickup at slower speeds, as compared with similar gas cars. (5) Maintenance. No oil changes. Brake wear is much lower, since is high percentage of braking is done by recharging the batteries instead of via friction brakes. (6) Space. At least in the Tesla, “the works” take very little room, leaving front and back trunks, as well as flat floor spaces in the car. (7) Modern computing/displays. This is Tesla-specific, but the use of large dispays, modern UIs and modern software distribution is a breath of fresh air for the automotive industry.

Downsides. There is no doubt, though, that there are some tradeoffs. (1) The major one is EV range and range anxiety. I will cover this below. (2) Car cost is certainly an issue for the Tesla. It is an expensive car. The Leaf, however, is very likely a significant cost saving for people who can fit its driving profile. It can save $1000 or more a year in gas. (3) Ability to charge. People who own homes, or who have EV-friendly employers can charge at home or at work.  However, people who need to park on-street may find that owning an EV difficult. (4) Unknowns. This is a new technology, and it’s too early to know how EV batteries will degrade over time, and how well the car companies will support them. Similarly, there is variation in the range of an EV depending on weather (the car may use energy to heat its battery in cold weather, and use of heaters or A/C reduce range), driving style, and the altitude profile of the road.

Range Anxiety. The Leaf and the Model S (85) are 2 competely different cars, and it is unfair to compare them.  After US and California rebates, the Leaf is $18K plus tax & registration, or ⅓-¼ the cost of an 85kWh Model S.  That said, it’s interesting to contrast a 70-mile range EV with a 250 mile range EV. Those number are my guesstimates for the range of the cars in mild weather, driving 65-70mph, and charging their batteries fully. Note, both manufacturers suggest that you don’t charge the battery fully, see Charging Level below.

I have no range anxiety when driving our Model S around the Bay Area. I would have to go out of my way to tax the car’s range. It is simply go, enjoy the drive, and plug in when you get home at night. However, should I need to drive out of the Bay Area, e.g. north to Napa or south to Monterey, I’d need to plan my driving. I’d make sure any side trips kept me in range, I’d stay under 70 mph, and, going south, probably visit the Tesla Gilroy Supercharger on the way in and/or back. Longer trips would definitely require visiting Tesla’s supercharger network, or searching for hotels with overnight 220v chargers–something I rarely do. When we travel to our cabin in the Sierras, not within range of a supercharger, we trade cars with one of our daughters. A trade like this might happen a few times a year. However, with our Model S we have taken trips to Lake Tahoe (480 miles round trip), Yosemite (420 miles round trip) , and Los Angeles (740 miles), but all have been carefully planned. Tesla superchargers (seehttp://www.teslamotors.com/supercharger), and/or overnight charging in hotels, or multi-day 110v charging, definitely make it possible to do long distance trips with the Tesla, but they aren’t everywhere. On the West Coast, one can now drive from San Diego to Vancouver, stopping perhaps for 45 minutes every 200 miles to charge. Thus far, I’ve used the Tesla supercharger network 10-20 times, and have never had an issue–the chargers have always been operational, and thus far I haven’t had to wait in line–they have 4-8 chargers per station.

The Leaf is very different. Though I love the car, one needs to plan much more often, and it may crimp your spontaneity. It’s easy to exceed the range of a Leaf or similar EV. Most days the Leaf does the job.  It is no problem for my typical day 25-mile round-trip to work at Google. I even have a friend who drives his Leaf 50 miles each way between Kensington, CA and Google/Mountain-View relying on charging at work and at home. However, days when we’d like to drive 60 miles (or fewer using A/C or heat) can get dicey.  On “my Tesla month”, if my wife plans to drive more than 50 miles on a given day, I’d trade her the Tesla for the Leaf. When one of us plans to drive a new local route, we likely Google-map the drive to get a mileage estimate and see if there could be an issue. On the other hand, for repeated predictable driving, it can be great and a money saver. The Leaf does have something similar to the Tesla supercharger.  There are several CHAdeMO stations around the Bay Area that can fully charge a Leaf in half an hour http://www.blinknetwork.com/blinkMap.html. My understanding is that it’s one-at-a-time charging, so adding 50 miles of range may require 30 minutes for charging plus perhaps another 30 minutes waiting. I haven’t used these for those reasons, but depending on your driving, these could be an option.

Normal Charging. Both cars accept 110v charging, 220v charging, and high-power DC charging (previously discussed). The Model S has an 85 kiloWatt-hour battery, and the Leaf’s is approximately 23 kWh.  Though 110v outlets are ubiquitous, charging with them is typically an overnight endeavor, and, quite honestly rarely used, as it they only add 3 miles of range per hour of charge for the Tesla, or 4-5 for the Leaf. I believe that 220v J1772 chargers are the workhorse chargers for most EV owners. (J1772 is a standard plug that works for the Tesla, Leaf, Volt, and probably most other current EVs).  At our home, we have a 220v 40a circuit that supplys 7kW loaded to the Tesla through J1772.  That charges at about 20 miles-of-range per hour for the Tesla and about 10mi/hour for the Leaf–the 2011 Leaf’s 220V internal charger only uses 3.3kW. Google’s chargers are similar. It would probably be difficult to own an EV without easy access to 220v charging.

The Tesla superchargers advertise 80kW to 120kW, though in my experience the high speeds only last when the battery has a very low charge, and power reduces to the 40kW rate fairly quickly. Still, one can (and I have many times) get 200 miles of charge in an hour or so, while getting coffee, eating, or shopping in an outlet mall. Tesla is in the process of building out its supercharger network, but if they are on the routes you want to drive, they make long distance EV driving quite doable.

Charging Level. Nissan suggests typically charging the Leaf to 80% (resulting in 50-55 miles), and the Tesla’s default setting is 90% charging, e.g. 225-mile range, presumably to preserve the lifetime of the battery. My philosophy has been to use the default 90% Tesla setting, unless we are taking a long trip. Thus, there probably have been only 10-15 times during the year that we’ve fully charged the car. Given the shorter range of the Leaf, we fully charge it half the time, and only use the 80% setting when I’m using it to commute to Google.

Driving Style.  All EVs use regenerative braking to recharge batteries. In both the Leaf and Model S, taking your foot off the accelerator pedal (depending on user-settings) can cause the car to slow down significantly. The Model S takes this to an extreme, and is mostly a one-pedal car. That is, you can do most of your braking by modulating foot-pressure on the accelerator pedal, and only using the brake pedal for hard braking, and for the last few mph of stopping. This is a different driving style than for “normal cars”, but one that is easily learned, and all Tesla drivers I’ve spoken to are happy with it.

Many EV drivers become inspired to drive their cars efficiently. The most effective way to improve miles-per-kWh in an EV is to reduce speed. For instance, one may gain 15% efficiency driving 65mph instead of 75mph, see http://www.teslamotors.com/blog/model-s-efficiency-and-range. Of course, improving efficiency by reducing speed can work for all types of cars.

Charging Cost. EV car charging costs are pretty straight-forward to calculate. Our Tesla gets a little better than 3 miles per kWh, and the Leaf can get better than 4. Compute your usage (multiplying in some slop for inefficiency) and multiply by your marginal cost per kWh from your electric bill. Converting to time-of-use metering, and charging at low-cost times (overnight) may save money. Additionally, some utilities offer special rates for EV electricity, e.g.http://goo.gl/r91INu, however the cost of installing a new meter and electric lines to your garage should be included in any potential savings. Many EV owners are also roof-solar-panel owners, but that’s a separate discussion.

Bells and Whistles. There are many other aspects of the cars, especially the Tesla, to discuss that are not directly related to the EV drive system. The Tesla’s 17” display is unique, are is its over-the-air software updates. The car has safety-tested very well. There are many online reviews that discuss these things, e.g. see http://lmgtfy.com/?q=tesla+model+s+review. One interesting feature is smartphone apps for viewing current charge, letting you know when charging is complete or car is unplugged, viewing car location, and modifying settings such as max-charge level.

Summary. The Tesla Model S shows what all electric cars can be in the near future. It is a no-compromise car with no in-area range-anxiety, and with significant advantages over gas cars. Its main disadvantage is cost. The Nissan Leaf is an inexpensive car, that can be driven gas-free for many people, most days, but its range limits are easily reached. It can be a great 2nd car for many people.

 

Hy Murveit received his BS/Engineering at SUNY Stony Brook in 1977, and PhD in EECS from UC Berkeley in 1983. He worked 30 years in the field of speech recognition at UC Berkeley, SRI International, Nuance Communications and Google. He was a co-founder of Nuance and was VP of Research and Development there from its founding in 1994 until 2001. Hy currently is a member of the self-driving car team at Google.