A lot of that pivots around what you mean by “norm”, right Steve?

Every so often I see an opinion piece like the one by Steve Hanley at CleanTechnica (which TBF is a heavy copy/paste/echo job based on an opinion piece by Christoph Schwarzer) around why we should expect DC fast charging (DCFC) to become The Way we refuel battery electric vehicles (BEV / EV). I think that’s crazy talk, and have to question the motives/agenda/acumen of anyone pushing that narrative.

That might sound mean or dismissive, so let’s walk through it. It might still sound mean at the end, but definitively not dismissive ;).

Before getting to why I think Christoph is wrong, I’ve included the abstract from his opinion article, and a quote below to provide some context.

Fast charging with direct current is the only economically viable and practical solution for public spaces in the foreseeable future, finds our author Christoph M. Schwarzer. He also dares to look into the more distant future and believes that DC will not only prevail in public spaces.

In the long run, only charging with direct current offers operators the prospect of profit from their investments in charging parks, transformer stations, foundations and roofs. Walch knows that there is money to be made from charging infrastructure, but that is yet to happen. In the meantime, EnBW has commissioned at least one site (on average) per workday in 2023 – all of them DC.

First thing, for Christoph this is primarily about public spaces and companies making money from charging. In that context, some of the argument makes sense, but it ignores the much bigger question “does public charging make sense for most EV owners”. I don’t think it does, even if you don’t own a driveway.

There are places where DCFC completely makes sense; fleet charging, taxis, ride share, and driving between cities. But are those common enough use cases where we should pivot the “normal” infrastructure around it, or is that an effort to make EV refueling more like ICE refueling? Should we replicate a model where there are entities in the middle driving up costs for their benefit, and not yours?

Speaking of costs, let’s dig into that first. DCFC infrastructure is expensive. Exponentially more expensive than AC Level 2 (L2). A L2 EVSE (electric vehicle supply equipment, aka charger) is just a 120/240V AC contactor that talks PWM to the car so they can negotiate an acceptable level of current. A cheap one is a couple hundred bucks. The fancy commercial kind that supports personalized billing is a couple grand. All of that runs off of standard 240V AC, usually at 60A or less per EVSE. So while still money, it’s not crazy money. It’s relatively easy to install everywhere. In Illinois, if you live in a building built in 2024 or later, you will be able to add it for the cost of some wire and an EVSE.

According to California, the average project cost for installing DCFC is $104,443, which includes some heavy California specific rebates. That makes sense. Slow DCFC is 25-80kW. Fast DCFC is 125kW+. Inverters that can manage AC/DC conversion at that level and the infrastructure necessary to support up to 350kW is expensive.

That’s just install cost. Energy charges are also higher. If you can charge where you live, and piggyback off of your per-kWh rate, it’s almost always going to be less expensive than paying the commercial rate + profit margin for a DCFC operator. The US Department of Energy has a little explainer. Simple numbers, I live near Chicago and pay $0.10 kWh at my house to charge our cars. If I go to the Electrify America two miles from my house, it takes less time, but I would pay $0.48kWh standard rate. I could opt into a $7/month fee to turn that into $0.36kWh. So best case, I pay more than 3x to refuel my car, and I have to go to a special place, deal with some hassle, and wait. How is that better than plugging in at home when I’m not using the car?

Of course, that assumes that the DCFC is working. Right now at that Electrify America location, two of the six chargers are broken. Want to guess how many times the L2 EVSE at my house was broken?

I’m sure you all feel that’s a very compelling argument about cost :). Let’s talk about where DCFC makes sense; speed. Here’s Steve:

To get faster charging, we need DC charging equipment, which bypasses the onboard charger and sends electrons directly to the battery. The lowest DC chargers provide 50 kW of power — five times faster than most onboard chargers can handle — and the most powerful are able to deliver 350 kW of power. DC chargers with even higher power are coming soon. In the US, the National Electric Vehicle Infrastructure act requires each charging location to have at least two 150 kW DC chargers in order to qualify for federal funding.

DC Charging Is The Future

In an opinion piece written for Electrive, free lance journalist Christoph Schwarzer says that DC charging infrastructure is the future — not only along major transportation routes but also at malls and shopping centers and eventually even in our homes.

Schwarzer gives several reasons for his forecast. The first of them is time. AC chargers simply take too long. He foresees people using DC chargers to replenish their batteries while shopping for groceries or doing other things that require less than 30 minutes to complete.


Steve is right, DCFC is faster. Faster is better, in some cases; like fleets, taxis, ride sharing, and road tripping. All of these have a single compelling reason for charging faster; the vehicle is being used, waiting for L2 is inconvenient. But, is faster necessary all the time? I don’t think so, and the numbers support my take on it.

In the US, the average driver puts in ~40 miles a day. The rest of the time, the car is just sitting around. Why wouldn’t we want to charge the car while it’s not being used, in a convenient, and cheaper way? Even when road tripping, L2 makes more sense than DCFC at the destination points. That includes a temporary destinations like a hotel or parking site. I don’t generally travel just to drive as fast as I can in a circle. There’s a purpose and the car will sit for long periods while I do things like sleep, hike, sight see, whatever. Personally, I would rather the resting place has 10-20 L2 EVSE that I can plug into and feel OK about sleeping/hiking/faffing around; than 1-4 50kW DCFC that I need to wait in line for, and hang around while it charges for 1-2 hours so that I’m not blocking it for other folks who need a charge. Sorry, I just don’t find DCFC a compelling argument there. It simply doesn’t make sense, even before we layer infrastructure and energy cost back in. DCFC is a less convenient scheme to deliver more expensive charging.

Now let’s talk about efficiency. Here’s Steve again:

Schwartzer believes that DC charging will become the norm for electric car drivers at home as well. That may seem counter intuitive, but the reason is the increase in the number of rooftop solar systems and residential storage batteries, all of which operate on DC. By having DC residential chargers as well, all those elements can share electrical power with each other without needing an inverter to convert DC to AC and vice versa. All conversions involve losses, and with electricity flowing back and forth between solar panels, EV batteries, and residential batteries several times a day, those losses will become significant.

So Steve is right, AC/DC conversion isn’t free – usually in the 1-3% range depending on inverter quality, temperature, etc. That is very true. But I struggle to reconcile those small efficiency losses with the infrastructure necessary to make Steve and Christoph’s vision actually work. We use AC to deliver electricity to homes and businesses. Only completely off-grid installations can operate in DC-only. Which means that for the majority of EV that AC/DC conversion is going to happen somewhere. It has to happen because the whole world distributes via AC (for good reason). We could change the L2 EVSE from a simple contactor into a contactor + inverter and deliver DC to the car. That would work, but that just shifts where the inverter located, and drives up L2 EVSE cost. It doesn’t change the model.

Changing the model means distributing DC directly to the car, without the inverter. In theory that is possible. We could embrace the vision suggested above where we directly connect DC PV to our cars, but that would require running DC wires (which run at variable high voltage) to step downs (or step ups) to the car (which are usually 400V or 800V), while also running it to local storage via MPPT. That’s complicated. What if your PV isn’t terminated where you want to charge the car? How do you distribute it? Oh right, that’s why we use AC. AC is much better at traveling distance over wires at lower voltages. And we already have those wires in place.

Looking just at the residential market, because that’s where this argument focuses. 91% of the PV installs use micro inverters (DC/AC inverters installed on the solar panel). Even when you have on-site energy storage (i.e. a battery), it’s highly likely that the all of the transmission between points is AC. AC from solar panel to the load center (breaker panel). AC from the load center to the all-in-one inverter battery. That’s how systems like Enphase and Tesla work; inverters everywhere. You can work around it, but it’s not common in areas with adequate infrastructure.

We use AC in point-to-point transmission in most situations. Our building run on it, converting as needed to DC. There might be room for disagreement around whether that is the ideal model, but there’s no space to disagree that it’s the model we have. I can’t see how it makes sense to change that just for the electric car.

This is the part of their position that I struggle with the most. It seems clear to me that the two haven’t thought through what they are suggesting, or there are industry forces at work trying to push a broken narrative (sorry, that would never happen :P). I don’t know. Maybe “crazy talk” is harsh, but whatever it is – DC everywhere isn’t in my, or most any end-user’s best interest.

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