*Note from Elizabeth: Tom is posting today!

We've been driving electric cars for a number of years. When our trusty Mazda Protege 5 that we purchased after Adam was born finally got too old to properly maintain, we first looked at hybrids, but then settled on the first of a series of Chevy Bolts that have come under our care. We leased a couple of different Bolts between 2017 and 2020, and purchased our current Bolt in 2020. In all that time, we had never taken a trip that would require stopping to charge the car part-way through the trip. The Bolts have been very capable of handling our normal usage – commuting to Oakland and San Francisco, ranging out for hikes across the East Bay and North Bay – with overnight charging from our garage outlet. I think the longest drive I ever took was a drive to Sacramento and back, a round trip of 120 miles or so, well within the capability of the Bolt. Any longer drives we've taken (to Southern California or our trip last July to Lassen National Park) have been with our gas-powered Honda Pilot.

This changed last weekend when we decided to drive down to San Luis Obispo to visit Adam at Cal Poly. The drive from our house to SLO is about 230 miles, right at the upper end of the Bolt's range. We didn't want to chance it, and so planned a stop on the way down in King City, about 170 miles from the house, where there are a few fast chargers on the EVgo network, something we got an account for when we got our first Bolt but haven't used in years (we're on the freebie "just pay us when you use it" plan).

The drive to King City was fine - a little more traffic than we expected, but nothing horrible. We arrived, found all of the chargers to be available, and plugged in with the car registering about a 44% charge. We found a little coffee shop around the corner and settled in to a nice iced coffee. Within 30 minutes the car was charged up to 80%, but without firm plans for charging once we got to SLO (we were spying another EVgo station near a supermarket), we went ahead and let the car charge for the full 60 minute limit EVgo puts on a charging session, getting us up to about an 87% charge before proceeding to SLO.

As it turned out, the hotel we stayed at had a couple of lower-speed charging stations, so that solved our SLO charging needs. We plugged in there (downloading another app to do it, EV Connect) and got back up to a full charge as we slept.

On the way back we initially planned to stop in Gilroy at another EVgo station, but as we arrived, two other cars had just pulled in to the stations that were showing as available on the app. We drove on about another 10 miles to Morgan Hill and found an open spot there (the last open spot of a bank of four chargers). Another iced coffee at a nearby spot; this time we only had it charge about 45 minutes, getting us from around a 30% charge up to about 75% before we unplugged and moved on, knowing that we'd be able to just plug in at home upon our arrival.

All told, a very successful trip! The stops we had to make to charge, while certainly longer than the five minutes you'd spend filling a tank with gas, didn't seem overly burdensome. Elizabeth and I are still doing intermittent fasting, but if we were lunch-eating people, these stops would have fit in perfectly with a stop for lunch. That said, the charging station at the hotel was an unexpected and pleasant surprise. Also, had we been on a longer car trip (say, down to LA, 360 miles away), we likely would have wanted to make two charging stops along the way, unless we had a guarantee of some kind of overnight charging once we got there.

Now for some engineering, economics, and environmental impacts.

Charging speed. Our 2020 Chevy Bolt has a battery that can store a total of 66 kiloWatt-hours (kWh) of charge, and a maximum charging speed of 55 kilowatts (kW). One might think that you'd be able to just divide – 66 kWh capacity ÷ 55 kW charging speed = 1.2 hours = charge from 0% to 100% in an hour and 12 minutes – but that's not the case. In order to promote longer battery life, electric car charging rates are modulated during the charge, going at a higher rate when the battery is at a low percentage but then tapering off as it gets closer to 100%. The EVgo app shows a cool graph of charging speed while you're charging so that you can see how it's going:

The Bolt's 55kW max charging rate is on the low end of electric car charging rates, as is the 66kWh battery capacity. For comparison, the Kia EV6 long-range model has a larger battery capacity (77.4 kWh) and a much higher maximum charging rate (233 kWh); the Ford F-150 electric extended range has a 131 kWh capacity and a charging rate of 155 kWh. How those larger batteries translate into range will, of course, vary with the weight of the vehicle and how you're driving it, but the faster max charging rates means that you can charge up much more quickly using one of the fast chargers, so long as you can find one that'll support the faster charging rate. The EVgo location in Morgan Hill had four fast chargers, but two of those four are limited to 100 kW, so even though a car could charge more quickly, you're then limited by the charger itself.

Economics: All told, we put about 470 miles on the car with this trip, using 130.16 kWh of electricity, which works out to about 3.6 miles per kWh. The charging sessions we did on the road and at the hotel cost us $43.65; we also charged again once we arrived home to get us back up to the full "tank" that we had when we set out. That charge (at our current off-peak overnight PG&E rate of about $0.40 per kWh) will cost us $14.08, so our total electricity cost was $57.73. Most of the gas stations we saw on the trip were charging about $5.50 per gallon of 87 unleaded, so that same $57.73 would have gotten us about 10.5 gallons of gas, putting our equivalent fuel efficiency just under 45 miles to the gallon. Not too shabby.

Carbon: Some rough math – in 2021, PG&E said that they're emitting 89 pounds of CO2 per MWh of electricity, so the 130.16 kWh of electricity we used for this trip put about 11.6 pounds of CO2 into the air. Had we burned the 10.5 gallons of gas noted above (at that really efficient 45 mpg equivalent), we would have released 210 pounds of carbon into the atmosphere. Taking that same trip in our Honda Pilot, which gets about 24 mpg on the highway, we would have used about 19.6 gallons of gas, releasing 392 pounds of CO2. Now, PG&E's electric power mix is very carbon-friendly – 50% renewable, 39% nuclear, 4% large hydro, and only 7% natural gas – resulting in a CO2 rate that's an order of magnitude below the national average, but even if we were charging in Texas (where electricity generation emits 856 pounds of CO2 per MWh), our electric car trip would have emitted 111 pounds of CO2, which is still half of what our theoretical super-efficient 45 mpg gas car would emit.

As I mentioned earlier, this trip to SLO turned out to be very successful, and it's opened up some possibilities that we might not have considered before. It also shows the work to be done, mostly on the availability of public charging stations. California has 14,000 public charging stations, which is a lot (the other 49 states combined have 37,000 public stations). The availability of public stations is important not just for those taking long trips, but also for people who don't have the luxury we have of plugging in the car overnight at the house. California committed to phasing out the sale of new gasoline-powered cars by 2035, which in some ways is right around the corner, but it seems eminently doable. With transportation making up 28% of the country's CO2 emissions, taking bold steps to lowering the CO2 emissions is an important component of our work to mitigate climate change.