Urban EV PT 3: e-MPG

The Conclusion

If you are like me I like to the get to the good stuff right from the start, get confused (and motivated), and then learn the explanation. So right here is the big chart of numbers this post is all about for me and what I spent the last couple weeks learning about.

If this all makes sense to you then great, I hope you find it to be useful. If not, also great keep reading and learn along with me.

Why Make This Chart

There are a few reports I have seen that indicate that the Tesla Model 3 Standard Range Plus does not live up to its reported range capability of 250 miles in the real world. Two of these are whatcar.com and youtuber Alex On Autos Model 3 Standard Range Plus in a two videos discussing their range test and viewer submitted efficiencies. In contrast, people seem to think that the Niro EV often matches or exceeds the EPA estimate in real world tests. How can I look at the real world test results of a video or forum post and understand if they match up with the published EPA efficiencies?

This sent me down the road of figuring out what the EPA estimates actually mean and how they were obtained. The first thing I noticed was that if you take the EPA combined city/Hwy eMPG and use that to calculated the estimated range you always came up short. You can do this calculation by using the EPA’s stat that a gallon of gas is the same as 33.7kWh. So if you do eMPG[mi/gal]/33.7 [kWh/gal]*battery[kWh], should give miles range where the brackets[] are units. Doing this, as I said, brings you up short of the EPA estimated range every time. Doing this for the Niro, range = 112/33.7*64=212 miles, well short of the 239 advertised. This lead me to my first bit of understanding.

Wall kWh VS Battery kWh

The reason that the method above comes up short is that in the eMPG is designed to tell you about the cost to operate the vehicle not help you understand its range. It is trying to tell you how far you will get for each kWh you pay for coming out of your wall. Very useful from an economic perspective but not so useful if you are trying to understand the range of the car. In this case I really want to know the miles per kWh stored in the battery!

So what went wrong in the equation above? The reason that my range is not matching up is that I am inadvertently mixing units. While kWh appears twice in the equation and seem like they should cancel they are in fact not the same. One is wall kWh which I will denote as “kWh-wall” and the other is battery kWh, “kWh-batt”. These are linked by an efficiency that determined by the charger during the EPA testing. So that kWh-batt= eff_charging * kWh-wall where “eff_charging” is a car+charger dependent efficiency which tells you how much of the energy makes it to the battery. This is very useful number because it allows us to calculate the range based on the eMPG and what we should expect for miles per kWh-battery.

$$range = \frac{eMPG\left[\frac{mi}{gal}\right]}{33.7 \left[\frac{kWh-wall}{gal}\right]}\frac{battery\left[kWh-batt\right]}{eff_{charge} \left[\frac{kWh-wall}{kWh-batt}\right]}$$

and

$$\left[\frac{mi}{kWh-batt}\right]= \frac{eMPG\left[\frac{mi}{gal}\right]}{33.7 \left[\frac{kWh-wall}{gal}\right]}\frac{1}{eff_{charge} \left[\frac{kWh-wall}{kWh-batt}\right]}$$

The mi/kWh-batt is a very useful number because this, or its inverse kWh-batt/mi, is what the car will report for its efficiency. So when you are looking at videos or forums you can compare their results with the EPA and see if the car is living up to expectations. Just what I want!

Something to note here is that I haven’t said which eMPG is used here, City, Highway or combined. The nice thing is the equation can be used to find the expected range driving around the city or entirely on the highway for long road trips. Just plug in the appropriate eMPG. So if a youtuber goes for a long highway drive to demonstrate the car, like WeBackTesla does, plug in eMPG (HWY) found at https://www.fueleconomy.gov and you will get the expected range and mi/kWh of the car for comparison in the highway driving scenario.

Getting the Efficiency

I have left out one key ingredient in the equation, the charging efficiency, “eff_charge”. This can be found directly by referencing the EPA filings by the companies published by the EPA here https://iaspub.epa.gov/otaqpub. In these documents they indicate they manufacture indicates battery size and how many wall kWh are used to charge the car back up after the test. I find it easier to just use the published range to estimate the efficiency. Using the range equation above we can plug in the expected range and the combined eMPG and solve for the charging efficiency. Once we have that we can plug in the City and Highway eMPG to get expected range in city only driving or highway only driving. Also the expected mi/kWh-batt you would hope to see the car report for the car to live up to expectations.

Results

In the chart above I solved for the charging efficiencies for a number of cars on the market (yellow row). I then used this to calculate the efficiency I expect to see reported by the car both as mi/kWh(blue row) or as wH/mi (white rows below blue). The mi/kWh is seen in the Niro and Kona and the wH/mi is reported in the Tesla infotainment.

By referring to the chart you can tell if a car is doing better or worse than expected compared to EPA estimates. For example, in the video by WeBackTesla he goes on a 272 mile highway drive in his model 3 standard range and reports 237 wH/mi. In this case, we can see that he did a little worse than the EPA estimate of 230wH/mi using a little more energy per mile. He claims he was averaging speeds in the low 70s and going faster sometimes so this seems to match up.

Youtuber NiroEVJ did a highway test with his Kia Niro and got 3.4 mi/kWh driving in the low 70s which is better than the 3.35 mi/kWh calculated for the EPA numbers. He also took a slower route in this video averaging 50-60 miles on slower back roads and got about 3.7 kWh which better than the expected highway efficiency and matches well with the “combined” numbers. Note for mi/kWh bigger numbers a better, more efficient more range etc., and for wH/mi lower numbers are better.

Tesla Mysteries

However, in the video by AlexOnAutos on his range test he concludes that he believes his Model 3 Standard Range Plus is getting 3.85 mi/kWh-batt. However, I think he is confusing battery kWh and he is actually using the wall kWh based on how he describes his math. He also complains that the range can possibly match the 240 miles advertised, only 192 miles, but he uses 50 kWh-batt for the size of the batter by I believe this incorrect with the actual size being closer to 54 kWh-batt (54.4 kWh seems to be the value in the EPA reports found at https://iaspub.epa.gov/otaqpub). More evidence from 54 kWh over the 50 kWh battery size possibility shown in the first column of the chart is that for the range to work out the charging efficiency needs to be 84%, which is much lower than the ~90% charging efficiency reported by Tesla in the EPA report. This also requires the Telsa to mi/kWh to achieve the range to be unreasonably high.

After receiving some comments on this he has another video going over viewer submitted values taken directly from their infotainment screen. From this he gets 4.2 mi/kWh-batt which is lower than the 4.63 mi/kWh-batt I am estimating for the combined driving efficiency but it is hard to say how the users submitting are driving. Some were doing much better than this though and met or exceed the necessary efficiency for the car to meet EPA expectations. In either case, we now have a concrete way to make that comparison. My conclusion is the battery must be closer to 54 kWh. An interesting note here in the documents submitted to the EPA the Standard Range (not plus) has the same size battery which probably means it is software limited.

The whatcar.com results indicating 3.1 mi/kWh I still cannot explain. They seem wildly off from what users are reporting on the internet, like the 4.2 mi/kWh in AlexOnAutos video. I recently learned that Tesla will lend you a car for a day so if I am able to arrange for that I will do my osn testing and post about it.

The numbers for the AWD long range is still a mystery to me though. The charging efficiency seems way too low which would seem to indicate that the battery size I am using is too small but 75 kWh is often stated. The EPA report for the car though seems to indicate that the battery weighs 480 kg and the specific energy is 150 kWh/kg. Multiplying this gives 72kWh which obviously much less than 75 kWh and will only make the charging efficiency worse. So I am not sure what is happening here.

Wrapping Up

Hopefully this gives you the ability to take the eMPG values and convert them to numbers that can be easily compared to efficiency numbers reported by the car to determine if the car is living up to expectations. Also hopefully this has helped to illuminte the difference between wall kWh and battery kWh and gives you tools to spot when people online are accidentally mixing a matching to give odd numbers. In my next post, I am going to talk more about range in particular.

As a parting note some additional resources. I have already mentioned https://iaspub.epa.gov/otaqpub for official reports on efficiency and range. To understand the testing procedure this document is very useful. The 2 big take awaya from this are that they measure wall kWh and that while the procedure talks about 5 driving schedules (further description here) They actually only do 2 of them, UDDS and HWFET, but they aren’t very representative of real world driving so they multiply by .7 to correct for this. For example the highway test never goes above 60mph and averages 48 mph, not very realistic.

Happy comparing!

Urban EV Pt 2: Test Drives

After getting the parking spot last Friday things kicked into high gear and I begin test driving cars. So far I have driven the Kona, Niro, Model 3 and a Bolt (I threw in an Ioniq hybrid since I was already at Hyundai). My first impression is that electric cars are amazing! They are quiet and smooth and the low end torque that everyone talks about really does live up to the hype, making the cars feel sporty and fun. And that is saying a lot because I am not really a “car person”.

Hyundai Kona EV Limited

The first car I drove was the Kona, and unfortunately I had a terrible time with the dealer. This particular dealer was selling the car with a 5K premium above MSRP and will barely let you test drive the car, limiting you to short drives of only a couple blocks. The saleswoman who was showing me the car was really nice though and broke the rules, letting me drive a lot further regardless of getting yelled by her boss for it.

Despite all that, I liked the car. It was small, only 164.6 inches long, which is a plus for city parking while still feeling spacious. The trunk was also large and with the seats down there is lots of storage. One thing I didn’t love about the car was the noise it made at low speeds to warn pedestrians. It was quite loud and I was always aware that it was there. Due to the nature of the test drive I never got to see what it was like on the highway so I’m not sure if it would go away.

The car is definitely a reasonable option so it is going to come down to things like price, range, and features. On this front the car seems great with the SEL trim level coming in at ~$36,500 MSRP with 256mi EPA estimated range. It also has a$7500 federal tax credit and in California another $2000 rebate. However, the Kona has one huge shortcoming for me summed up with one image. To get Smart Cruise Control (SCC) with Stop & Go you have to get the Ultimate trim which is considerably pricier, and with my long commute this is at the top of my list of features. Given this I am not sure if the need to buy the Ultimate will be a deal breaker, but we’ll see how it stacks up against the other options. The other feature I am looking for to help with the commute is the Lane Keep Assist which comes standard on all trims. I couldn’t actually get this working on the test drive, possibly due to the low speeds, so I can’t attest to the quality. A full comparison of options on the trims can be found here. Kia Niro EV EX The next car I drove was the lower trim of the Niro. The car is a really compelling option with a MSRP of$38,500 along with the $7500 federal tax credit and$2000 rebate in California. It also comes standard with Smart Cruise Control and Lane Keep Assist. This means that the car will, for the most part, drive itself on the highway something akin to autopilot by Tesla. I had a chance to try this feature on the test drive while we were driving on the highway, and in my opinion it worked great. It stayed between lane lines and slowed down for the car in front of me, and I found the controls for changing following distance and turning on the cruise control and lane assist to be intuitive.

Other things I liked about the car were: the intuitiveness of paddles on the steering wheel to change how aggressively the car regenerated when you let off the accelerator, the large trunk and hatch back, and good sized back seat. Really the only bad thing I can say about the car is that all the seat controls were manual, as is the hatch back, but I don’t really care about that. The higher trim adds electric seats, leather, sun roof, parking distance warning, and a better sound system with a price tag of $44K ($45K for the launch edition which adds LED headlights and auto dimming rear view mirror).

All in all, I really liked the Niro. With a range of 239 miles and all the major features I want, and with a very reasonable price tag for an EV (especially with rebates), I expect it will be a top contender.

Tesla Model 3 Standard Range Plus

I am not going to say as much about the Tesla because the car is already so well known, or at least it is to me. The biggest thing about the Tesla is that it clearly has a much more luxurious feel. For one, it is bigger which helps, but also the seats are a vegan leather, there is a large display with an aesthetically pleasing layout, it has power seats, and the trim and buttons all looked appealing. I was also pleasantly surprised at how large the trunk was. Also in the pro column is super charging, autopilot with the possibility of upgrading to the full self-driving package, and the general “wow” factor. On the last point, much to my chagrin, people actually said “wow” when I told them I was considering buying one. This is in contrast to the look of confusion about the other three options.

Comparing this with the Kona and the Niro, at approximately the same MSRP of $39,500 and range of 250 miles, the Tesla definitely offers more features. The big difference are the rebates which are only an$1875 federal tax credit that ends on Dec. 31st and the CA state rebate of $2K. I actually put in an order for the Tesla to try to beat the deadline in case I decide I want it, only losing the$100 order fee if I decide to cancel. The other aspects of the Tesla that are somewhere close to the con column are that the shape of the car isn’t my favorite, specifically the back end, and there isn’t a dashboard directly in front of you, but I didn’t notice it too much while driving. Another thing that was a little difficult for me was the side-to-side clicks on the steering wheel buttons, which seemed a bit stiff and a little too far in to be comfortable. The vertical scrolling was fine. Lastly, the aerowheels are a bit ugly but I have been assured they can be removed to reveal a much nicer wheel.

Ultimately, I think the decision here will come down to whether I think the price is worth having access to superchargers and a nicer interior.

Chevy Bolt LT

I am going to wrap up with a quick note about the Bolt. I only drove it briefly and I didn’t really like it before I tried it, and the test drive didn’t change my mind. The car just feels kind of like a cartoon car. I don’t know exactly what it is but I think it may be how squat but tall it is. Also, everything on the interior is manual (even in the premium), the infotainment center felt a little clunky, and the trunk feels shallow. Premium trim adds leather seats but I doubt this would fix my perception of the car.

The biggest thing I got from the test drive was that to get the cruise control and lane keep assist I would need to get the Driver Confidence Package 2, though the car I tested didn’t have it. The result is this means a MSRP for a LT trim level of ~$39K. Chevy is offering pretty large rebates, bringing this down to about$31K in order to compete with the Kona and Niro, though.

Bottom Line

Right now it looks like a race between the Kia Niro and the Tesla Model 3. The Kia because it has the larger rebate and all the features I want, and the Tesla because it offers more features for the same MSRP along with the supercharging network. In a future post, I will collect statistics, prices/rebates, and features and try to parse out which option is really the best value based on what I want and how I expect to use the car.

Urban EV Pt 1: Over Coming

This is the first in a series of posts about owning and operating an electric only vehicle in an urban environment. I, myself, live in an apartment and commute approximately 80 miles each day (40 miles each direction), of which about 35 miles are on the highway and the other 5 miles on city streets. Up until recently, I only had access to street parking and the uncertainty of charging was an insurmountable hurdle to buying an EV. However, on Friday I was able to rent a parking spot with a dedicated electric charging station!

I found the spot by watching Craigslist over the past month or so and emailing promising postings about the possibility of charging an electric vehicle. I had some notions about how I might make it work, even with 120V “level 1” access, by mainly using DC fast charging to fill up and using the outlet to add a little charge each night so I didn’t have to go to the fast charger as often. I was lucky enough to find a spot with a level 2 charger already installed, which can deliver up to 7kW. The charging station is run by greenlots and costs between $0.21-0.43 per kWh depending on the time of day and energy costs. At night, when I expect to be charging, it tends to be at a low end, costing$0.21 per kWh. For reference, for a 64 kWh battery it would cost about \$13.50 to fully charge.

The downside is that the spot is a little far from my apartment (~.6 miles), so I am hoping I will only have to go there every 2-3 days. I also have the possibility of charging at work, but there are limited chargers and to use them you have to sign up for a program that currently has a wait list.

Anyway! I am very excited about the ability to have guaranteed charging. It was the last thing preventing me from buying an electric car. As many of you in urban environments know, there are chargers around like ChargePoint but they are often in parking structures that cost a lot to park in and sometimes you can’t leave your car overnight which is kind of a deal breaker. That, along with the uncertainty of my work charging and reports of often broken fast charging, were enough to dissuade me until now.

I know finding a magical parking spot with a charger isn’t an option for everyone (and if mine disappears may not be for me either), so once I own a car I will explore other ways to charge. But for the moment, I will take advantage of the opportunity and use it as a springboard for getting my electric car dream off the ground!