Strategies to Save Money When DC Fast Charging

I’ve been hearing and reading a number of stories claiming that it is extremely expensive to DC fast charge a non-Tesla electric vehicle away from home, and while there is some truth to that, most of the stories are gross exaggerations that leave out key details. In this story, I will provide a more accurate representation of the costs of using the public fast charging infrastructure, and I will explain some of the common pitfalls that lead to overpaying when charging away from home.

Tesla Supercharger Network Pricing
Before I dive into the costs and quirks of the public charging infrastructure, I want to acknowledge a few advantages that the Tesla Supercharger Network has over the public charging providers. This is partly to set a baseline for comparing Tesla’s private network and the public charging providers; however, it is also because most of the misinformation I hear about the public charging infrastructure is coming from Tesla owners.

Typically, those Tesla owners rarely use the public charging infrastructure (by using an adapter or a second, non-Tesla EV), or in many cases, it appears that they’ve never actually used the public networks themselves but rather are parroting something they’ve heard or read elsewhere. Either way, as you’ll see from this story, most of the misunderstanding about how the public charging networks operate is based on a lack of experience and infrequent use (which means they typically aren’t paid members – I’ll address the impact of that on pricing later in this story).

The key advantage of the Supercharger Network is that it is a single, proprietary standard. For Tesla owners, this means that everything is tailored for their vehicles. The speed of the Superchargers is matched to the speed of their vehicles. Because the network is subsidized by Tesla owners, the prices are low and the pricing structure is uniform. Finally, Tesla owners can plug in without the need for an adapter. That CHAdeMO-to-Tesla adapter is required for Tesla vehicles to use the public charging infrastructure, and it is only capable of maintaining a peak charging rate of 50 kW (significantly slower than both Tesla vehicles and the newer public charging sites).

Tesla fee structure is based on the kWh of energy delivered whenever possible, though some regions still prohibit non-utilities from selling energy directly to the customer. Currently, the cost of using the Tesla Supercharger is $0.26 per kWh, so Tesla owners can expect to pay anywhere from 6 to 13 cents per mile (assuming typical freeway efficiencies ranging from 2 mi/kWh to just over 4 mi/kWh).

Memberships Alter Prices
One of the biggest disconnects driving this myth about extremely high prices for public DC fast charging is due to the fact that most people do not frequently use those networks, so they are experiencing a different pricing structure than those of us who do. For Tesla owners, they’re in the Supercharger club regardless of whether they asked to be; however, few non-Tesla electric vehicles come with upfront memberships to the various public charging providers, so those owners actually have to seek out and pay for a full membership.

Full memberships with public charging providers typically result in two major pricing advantages. The first is an elimination of “session fees.” Networks such as Electrify America and EVgo will charge non-members an upfront session fee. Essentially, if an EV owner doesn’t use a network frequently, they might not want to pay for a monthly membership. At that point, they would simply pay at the charger using a credit card, but they would pay a more expensive price for the charging session because of the upfront session fee.

The other way membership pricing differs is that most public charging providers currently set fees based on a per-minute usage, and full members are charged a lower per-minute fee than non-members. With modern electric vehicles, even DC fast charging sessions can range from 20 minutes to an hour, so even a 5 to 10 cent per minute difference between a member and a non-member can be significant.

On a common 30-minute session that might only add 100 miles of range, a $1 session fee and $3 cost difference due to a higher per-minute fee increases the total cost by 4 cents per mile. That could represent a 40% to nearly 70% price increase over what members pay on those same networks.

I’ve found that many of the paid memberships actually save money, even on the first charging session. For example, Electrify America’s full membership costs $4 per month, so that cost would be recouped in a single 30-minute charging session.

Adjusting to Per-Minute Pricing
Per-minute fees do serve a purpose for the public fast charging infrastructure because they prevent electric vehicle owners from “squatting” at public charging stalls for prolonged periods. However, per-minute fee structures can cause significant issues if they are not implemented properly.

The first issue with assessing fees on a per-minute basis is that most electric vehicles see significantly slower charging speeds over time. These reduced charging rates are referred to as step downs or tapering. Electric vehicles such as the Chevy Bolt EV, Hyundai Kona Electric, Kia Niro EV, and the Tesla Model 3 will be charging at half their peak charging rates by the time they reach 65% to 75% battery. That means that when using networks that assess per-minute fees, charging past that point will literally double the cost per mile.

This per-minute fee is exacerbated when the public charging provider uses chargers that vary in speed. Currently, the best example of this is EVgo, whose chargers range from 40 kW all the way to 350 kW, but all of those chargers cost the same per-minute fee, which is based on the region rather than the charger itself.

As a Bolt EV owner and full member with EVgo, I pay 26 cents per minute in the Greater California region. If I drive out to EVgo’s 350 kW fast chargers in Baker, my Bolt EV can add over 26 kWh in 30 minutes. If I drive up to Tahoe and use one of EVgo’s 40 kW Drive the ARC chargers, my Bolt EV will only add about 19 kWh in 30 minutes. Both sessions cost me $7.80, but on the 350 kW Baker charger, I am paying 30 cents per kWh or 7.5 cents per mile at 4 mi/kWh. However, on the 40 kW Tahoe charger, I am paying 41 cents per kWh or over 10 cents per mile at 4 mi/kWh.

These per-minute fee structures are also what throw many Tesla owners off when assessing the cost of the public charging infrastructure because their only way to access those DC fast chargers is by using a CHAdeMO-to-Tesla adapter that is restricted to 50 kW. If the Tesla owner is not a paid member of Electrify America or EVgo, they can expect to pay at least 25 to 30 cents per minute while receiving no more than about .75 kWh per minute. That means that even Tesla Model 3 owners (Tesla’s most efficient car) can expect to pay at least 10 cents per mile when using an Electrify America or EVgo site, which could be 25% to as much as 50% more than a Chevy Bolt EV, Hyundai Kona Electric, or Kia Niro EV owner might pay to use the same site.

Adjusting to Demand Charging
While Electrify America also uses a per-minute fee structure, unlike EVgo, Electrify America’s fees account for the difference in charging speeds. Their fee structure has three tiers based on the charging speed of the car.

Electrify America’s base pricing tier is for EVs with peak charging rates below 75 kW, and the fees range from 18 cents per minute for members to 25 cents per minute for nonmembers. The second tier is for EVs with peak charging rates between 75 kW and 125 kW, and the fees for that tier are 50 cents per minute for members and 69 cents per minute for nonmembers. The final tier is for EVs with peak charging rates over 125 kW, and those fees are 70 cents per minute for members and 99 cents per minute for nonmembers.

These pricing tiers have caused cost issues for a number of electric vehicle owners whose EVs have peak charging rates near the bottom of middle tier. In particular, Hyundai Kona Electric and Kia Niro EV owners have been affected the most because their vehicles barely touch peak charging rates of over 75 kW, but they are being charged for a pricing tier designed for cars that charge at over 100 kW. The problem is compounded when those Kona and Niro owners aren’t Electrify America members because they end up paying both a $1 session fee and 69 cents per minute instead of the 50 cents per minute with no session fee that a full member would pay.

While there’s no easy way for Kona and Niro owners to get around Electrify America’s pricing structure, they can mitigate the high costs by being a member and not charging past their first charging rate stepdown between 55% and 60% battery.

A Kona Electric or Niro EV can charge to about 60% battery in 30 minutes on an Electrify America charger, adding a little over 37 kWh. For nonmembers, that would be $1 plus 69 cents per minute (a total of $21.70 for a 30-minute session). That results in over 58 cents per kWh or over 14 cents per mile.

For members, however, it would cost 50 cents per minute with no session fee (a total of $15), so Kona Electric and Niro EV owners who are members would be paying just over 40 cents per kWh, or about 10 cents per mile.

Idle or Parking Fees
In my opinion, the only acceptable way to implement per-minute fee structures is when they are used to supplement a per-kWh fee structure. Because the primary purpose of per-minute fees is to prevent electric vehicle owners from occupying a charger longer than they need to, the fees shouldn’t activate until after a set period.

For example, EVgo could structure their pricing so that they charged 30 cents per kWh (rather than per minute), but after 30 minutes, they charge an additional 10 cent per minute fee. Using my example from above of charging my Chevy Bolt EV on two different EVgo chargers, after 30 minutes on the 350 kW Baker charger, I would be paying the same $7.80 for the session, resulting in the same 7.5 cents per mile. However, on the 40 kW Tahoe charger, I would only be paying $5.70 for the session, which would then decrease my cost per mile to the same 7.5 cents per mile as I was paying on the faster charger.

Perhaps the faster 350 kW charger can have an additional 10 cent per minute fee that starts after 30 minutes while the slower 40 kW charger starts charging that additional fee after 45 minutes or an hour. That structure would provide owners with a more universal experience while discouraging people from monopolizing the station for extended periods.

Conclusion
Right now, charging your EV away from home can be complicated if you are relying on the public charging infrastructure, and it can be expensive if you are not a member or don’t adjust for per-minute and demand-based pricing structures.

Luckily, states like California have passed regulations that will require public charging providers to charge on a per-kWh basis, and hopefully, the public charging providers will adopt those fee structures nationwide. Until those changes in pricing happen, however, electric vehicle owners need to be aware of how the speed and pricing structure of the charging provider and specific chargers affect their costs.

Unfortunately, for now, many EV owners still don’t have a choice in which charging provider they use, but when choices are available, it’s worth the time to assess which networks are the most cost effective and use the strategies I outlined in this article to mitigate costs.

See you next time as I provide a detailed breakdown of costs for using the public fast charging networks in my 2017 Chevy Bolt EV!

About The Author
Eric Way focuses on reporting expert opinion on GM brand electric vehicles at Torque News. Eric is also an instructional designer and technical writer with more than 15 years of writing experience. He also hosts the News Coulomb video blog, which focuses on electric vehicles, charging infrastructure, and renewable energy. Eric is an active member of the EV Advocates of Ventura County, a volunteer organization focused on increasing the widespread adoption of electric vehicles. You can follow Eric on News Coulomb