So the 2005 Toyota Sienna needed to be replaced, and I got a 2017 Nissan Leaf. This particular model is an S trim (read cheap) in Red. So now that I’ve made the leap into electric vehicles, it is time to determine what the options for charging are. I’ve had the car for about 2 weeks as of this writing, so I am definitely not an expert. So there may be some inaccuracies in the information below.
Fortunately at work I have free EV charging, so knowing how the public charging works is part intellectual exercise, as well as a preventative in the case where I really need it. Right now I don’t have an EV charger at home (and neither do I have solar).
For reference, my Sienna would run at about 16 mpg, and I would get around 350 miles for a full tank of gas of around 18 gallons. So a full tank would be around $80. More on this later.
Charging in the South Bay area of Silicon Valley has a few options, with a charging option usually being within a few miles. The most popular options are Chargepoint, EVgo, and Volta. Some cities (eg: Palo Alto) and some stores (eg: Best Buy) have free charging (typically through Chargepoint). There are also some interesting charging deployments coming up through companies like Powerflex, where the Mountain View/Los Altos school district is deploying charging for school staff with discounted rates after hours for the public.
Different public companies have different ways of charging. Chargepoint is typically charged at a rate per hour, pro-rated against usage. EVgo charges per minute. Blink apparently charges per kWh for their chargers. I’ve had a quick play with charging at both Chargepoint and EVgo stations, so the following represents how I see charging working. The sample space is small (three charging sessions), but the numbers seem to reflect what I’ve been seeing implied with blogs.
So let’s start with Chargepoint. I’ve used Chargepoint at Best Buy, City of Sunnyvale, and Cupertino Rotary club. The Sunnyvale Best Buy charger was broken, the Chargepoint would detect and start, but would never deliver any power. It is marked as Free, so it might be a good option if it worked. It might be that the charger locking head was broken and so was unable to “lock”, and so would fail. Interestingly, Chargepoint didn’t notify that there was a problem.
The other times I’ve used Chargepoint it worked as expected. You swipe, plug in, and the charging starts. You go do what you need to do and come back, and be on your way. In both these cases, the systems where 6.6kW rated units. According to the Chargepoint app, one provided 6.0kW, the other 6.5kW. Since Chargepoint charges per hour (or part thereof), a poor charger choice could make quite a difference. In these two cases, I was there for just under an hour and had around 6kW added to the car. This is equivalent to about 20-24 miles. Not bad for around $1.50. Both City of Cupertino and City of Sunnyvale both charge $1.50/hr for charging.
Now EVgo is a bit different, they have DC chargers, capable of delivering about 40-50 kW. I charged for just under 8 minutes at an EVgo station, costing $2.10 (they round down, which is nice). They delivered 5.8kW of power in the 8 minutes.
DC chargers generally only deliver power to 80% of full, so there are some unusual behaviors that happen on the way to 80% that are actually quite important. In the case of EVgo, I was monitoring the power with the Leafspy Pro app on my phone as it was charging. The image below is a screenshot.
As you can see the initial charging power (green & blue line) was around 46kW for the first few minutes, and then began to drop off as the system approached 80% (red line). This is not unexpected, but it does have an impact on the overall power delivery for a session. The initial rate was 46 kWh, the final rate was around 41 kWh, and the average was around 43kWh.
The table below tabulates the costs as rates for the different charge rates that I used.
| EVgo||DC|| 5.816||$2.10||8||$0.36||43.99|
| ChargePoint||Level 2|| 5.403|| $1.37||54|| $0.25|| 6.00|
By comparison, the PG&E charge rate is $0.22 for Tier 1 or $0.27 Tier 2 for the base E-1 rate plan, or for my bill (which includes the Silicon Valley Clean Energy Electric option) it comes at around $0.21 or kWh. So with my current usage, the a good Chargepoint Level 2 charger will be cost equivalent to my plugging in at home with the E-1 rate sheet.
I’ve applied for the EV-A rate sheet from PG&E, even without the EV it would actually save me about $10 over the course of a year. With the EV-A rate sheet, PG&E provide Peak at $0.49, Part Peak at $0.27 and Off Peak at $0.13 during Summer. During winter, it is $0.34, $0.21, and $0.13 respectively.
The three options that I haven’t used yet are Blink (apparently $0.49/kWh for DC fast charging), Powerflex (apparently $0.15/kWh with a mix of DC and Level 2), and Volta (apparently Free).
So with the EV-A rate plan it is considerably cheaper to charge the car at home off-peak vs a public charger. Powerflex is not local to me, but intriguing and useful in a pinch, and Volta stations tend to be fairly busy (free of course is always in demand). Blink seems to have a charging model that would be a last resort.
With all the per hour charging systems, you really want to ensure you get the best bang for your buck, so you should make sure you know which chargers deliver the highest power. A good Level 2 can provide 6.6kW, but a poor one can deliver considerably less. Knowing the good Level 2 chargers can give you an effective 10% discount on pricing. With a DC charger, it looks like you want to do the same, knowing that the stakes are even higher.
Finally, public charge stations that charge per hour, really are intended to move you from empty up to something safer, but you shouldn’t expect that they should fill your car up. For DC, you definitely start getting power limited at around 65%, and with Level 2, I’d expect you can go higher, but you’d find the charge rate would begin to drop off for the final trickle charge.
If in the end, I don’t have charging at work, I’ll likely charge at home and be comfortable knowing that home charging provides very attractive pricing with the convenience of a full car first thing in the morning.
I’m likely to go Solar before the end of the federal tax credit, so then it will completely change the equation. I’m paying close to $2000/year for power, so with the new Tesla Solar pricing (around $8000 for a 4k unit), it will likely pay itself off within 5 years, even up front.