Electric Vehicle Charging Overview. E car charger

How to Charge an Electric Car

Electric vehicles (EVs) are powered by batteries that provide energy to electric motors, driving motion to the wheels. Keeping the battery charged is key to keeping the vehicle moving and is just as easy as filling up on gas in a gas-powered car.

We’re here to explain all you need to know about charging an electric vehicle: step-by-step instructions, where to charge, how long it takes to charge and how far a charge lasts. We’ll also cover the different charging station output levels, the average cost of charging an EV and how to monitor your charge status.

How does charging work?

Charging occurs by connecting the EV to a power source known as a charging station. Once connected to the charging station, EVs use their charging port and onboard charger to convert the external power into battery charge. While all-electric cars (BEVs), such as the Tesla Model 3, must be repowered at a charging station, hybrid vehicles (HEVs and PHEVs) can be recharged at a charging station or refueled at a gas station.

Please return your EV rental with its battery charged to at least 10%. If you charge at a Tesla network station, we’ll pass through charging-related fees to the credit card you used to rent your Tesla. And if you charge at a third-party charging station, just pay on the spot.

EVs are able to charge at three different levels of power output. These different output levels impact where you can charge (home or public location) as well as the equipment and time required to charge. Home chargers use Level 1 or Level 2 charging equipment.

Level 1 uses a standard household outlet (120-volt connection).

EVs come with a standard 120V charging cord so you’ll be able to charge if you have access to an outlet.

Level 2 uses a higher 240-volt power source and can be compared to the power grid your oven is plugged into and charges much quicker than a Level 1 outlet.

DC fast chargers are found at public charging stations. These provide quicker charging times than Level 1 and 2 stations and are ideal if you require a boost of power in a shorter amount of time.

EV batteries also receive power through a process called regenerative (regen) braking. Regen braking uses torque to slow the car, recapturing energy that is normally lost in non-electric cars by using an inverter to invert energy from the brakes.

While regen braking does improve the battery charge, it is not the primary source of recharging for all-electric vehicles (BEVs). For maximum performance, a charging station is required to repower the battery.


Recharging an EV is just like filling up with gas, but rather than inserting a nozzle at a gas station, you insert a connector at a charging station. Use the following steps to charge Model 3:

  • Open the charge port cover via the touchscreen or by pushing on the cover.
  • Remove charging station connector from dock and insert into the car’s charge port. While charging, the charge port logo will flash green.
  • The touchscreen will inform you of charge percentage and estimated time remaining. To optimize battery performance, your rental car will charge to 90%.
  • When complete, press the connector button until the logo turns white, remove from car and return to dock.

While Model 3 is compatible with all EV charging stations, an adapter is required when using non-Tesla stations. Each of our Model 3 rentals comes equipped with a Mobile Connector kit which includes the adapter. After using the adapter, always be sure to remove it from the charging station connector and return it to the Mobile Connector kit.

Where can I charge the car?

As well as charging at home, public and private charging stations provide you with a place to recharge and restart your journey. There are currently over 40,000 official public charging stations available across the US, with nearly 100,000 charging outlets installed in public spaces. To meet the increasing demand for electric car energy, stations are rapidly being installed nationwide.

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Requiring only limited space, EV charging stations can exist in similar locations to gas stations, such as off the highway or even at gas stations, and in locations not suitable for gas stations. Such locations include public parking garages, office and retail parking lots and even busy downtown streets.

There are a variety of ways to locate public charging stations. In Model 3, Tesla Supercharger stations appear as red pins on the navigation screen. You can also touch the lightning bolt on the touchscreen or ask for location options via voice command.

Apps, such as Plugshare and ChargePoint, are available as well to pinpoint your nearest charging location. You can also visit the US Department of Energy website and use their charging station locator to find stations throughout the US.

How long does it take to charge an electric vehicle?

Electric car charging times vary depending on the size of the battery and the charging station output. The vehicle model affects the charge time as well, with manufacturers like Tesla, GM and others having different models that offer varying charge periods.

If you know the power output level of a charging station, you will know whether to expect a slower or faster charging experience. When available, we encourage you to select charging stations in the following order:

  • Tesla Superchargers: Add up to 200 miles in only 15 minutes
  • DC fast chargers: Ideal for longer journeys requiring short stops
  • Level 2 (240V): Achieve a partial to complete charge in 5-8 hours
  • Level 1 (120V): Convenient for home or local driving use, not for long trips

How much does it cost to charge an electric car?

Charging an EV at home has been found to be the most affordable and common option, with owners typically doing 80% of charging at home. The average EV-owning US household pays 12 cents per kilowatt-hour (kWh) of energy used to charge, adding on average 30-60 to a monthly energy bill.

While you’re likely not home while renting a car, our Model 3 rentals include a Mobile Connector kit which enables you to connect the car to a standard 120V household outlet should one be available during your trip. Additionally, the home charging savings are worth noting when comparing refueling costs of gas-powered cars.

So how much does it cost to charge an EV at a public charging station? In short, it varies, but is always more affordable – and greener – than filling up with gas. Although free public charging stations do exist, most stations charge a fee based on kWh usage, charging time or percentage of battery charged.

The costs of charging can also vary depending on your location. Home charging, for example, varies from an average of 8.65 cents per kWh in Iowa to a rate of 32.76 cents per kWh in Hawaii. Just as home charging rates vary, rates at public charging stations can vary – even within the same city. Apps, such as Plugshare and ChargePoint, can reduce charging costs by locating free or less expensive charging stations in your area.

No matter the distance of your journey, charging an EV is sure to provide cost savings compared with fueling a gas-powered car.

How far can an electric car go on one charge?

Electric cars are capable of reaching different driving ranges, depending on:

Make and model Size of the battery How much the battery is charged

Most EVs easily travel over 200 miles on a full charge, with select Tesla models reaching beyond that. The Tesla Model 3, for example, can travel up to 260-mile range. With electric vehicle technology advancing all the time, these ranges are estimated to increase over the coming years.

Just like a car powered by gas, weather conditions and the style in which you drive an electric car will affect how much power the car has. For example, harsh braking uses more energy whether a car operates by gas or electric. Exercising safe driving practices will stop the car from wasting vital energy that could get it further down the road.

Likewise, using power-draining instruments and accessories onboard can deplete the battery. This includes entertainment systems, lighting and air conditioning.

Monitoring your Model 3 charge can be done in multiple ways. Displayed in a prominent location on the touchscreen, the battery meter reflects the charge remaining with numerical percentage, a status bar and color changes (green to yellow to red), and the battery range displays estimated miles remaining. Using Model 3’s voice command technology, you can also ask your car for an update on its battery charge.

Although unlikely to occur if you are monitoring your charge, Model 3 provides plentiful alerts and warnings as well as suggested nearby charging station locations via pop-up notifications if a low charge is detected.

Ready to recharge and rethink the way you drive? Learn more about EVs by visiting our electric car hub for more information.

EPA estimate according to Tesla, Inc. product specifications.

See your EV Rental Terms to learn more

Electric Vehicle Charging Overview

Imagine never having to stop at a gas station again – and instead, having an unlimited supply of fuel available at home or wherever you normally park. For many electric vehicle (EV) drivers, this is a reality. Battery electric vehicles never need gas, and for short trips, plug–in hybrids might use no gas.

EV charging is simple, cost–effective, clean and convenient, particularly when you are plugged in at home – filling up your car, even while you’re asleep.

There are three categories of electric vehicle (EV) charging: Level 1, Level 2 and DC fast charging. Levels 1 and 2 charging use a universal connector that can be plugged into any EV. DC fast charging uses three different connector systems called CHAdeMO, CCS Combo and Tesla Supercharger.

Although EV drivers primarily charge at home, workplace and public chargers are increasingly available in communities nationwide. Use our EV Charging Station Map to find nearby charging stations.

Level 1 Charging

Level 1 is the slowest method of charging but is sufficient for drivers who charge overnight and travel 30–40 miles per day. Charging cables usually come with a vehicle and plug into a standard 120–volt AC outlet with no equipment installation required. Level 1 charging works well for charging at home, work or anywhere a standard outlet is available – and when you have sufficient time to charge.

Level 1 charging uses a standard J1772 or Tesla connector that can plug into any EV, either directly, or through an adapter.

Level 1 charging adds about 3.5 – 6.5 miles of driving range per hour of charging time.

Level 2 Charging

Level 2 charging is considerably faster, but requires installing a charging station, also known as electric vehicle supply equipment (EVSE). EVSE requires a dedicated 240–volt or 208–volt electrical circuit, similar to what is required for a clothes dryer or electric range. Level 2 is found at many public and workplace charging stations, but also in many homes. It uses the same standard connector as Level 1 charging, meaning any EV can plug in at any Level 2 charger.

Level 2 charging uses a standard J1772 or Tesla connector that can plug into any EV, either directly, or through an adapter.

Depending on battery type, charger configuration and circuit capacity, Level 2 charging adds about 14 – 35 miles of range per hour of charging time.

DC Fast Charging

DC fast charging, also called quick charging or supercharging, provides the fastest available fill–up. It requires a 480–volt connection, making DC fast charging unsuitable for home use, and not every EV model is equipped for it. Stations offering DC fast charging are found in shopping centers and often along major travel corridors, allowing EV drivers to charge up quickly and take longer trips.

DC fast charging uses CHAdeMO, CCS or Tesla connector systems. Check with your vehicle manufacturer to determine if your car has fast charging capability and what connector systems are compatible with your EV.

Depending on battery type, charger configuration and circuit capacity, DC fast charging can add up to 100 miles of range in about 30 minutes of charging time.

Electric Vehicle Charging Costs

Home Charging CostsThe cost to charge your electric vehicle depends on your vehicle’s battery size and the price of electricity where you live. Most utilities offer time–of–use (TOU) rates that greatly reduce costs associated with charging a vehicle at home by charging during off–peak hours. Contact your utility to find out more. 1

While electricity costs vary greatly, the average cost of electricity in California is about 16.58¢ per kilowatt hour (kWh). 2 At this price point, charging a 40–kWh battery with a 150–mile range would cost about 4.42¢ per mile (or about 6.63 to fully charge). Meanwhile, fueling a 25–mpg gas vehicle at California’s average gas price of 3.11 per gallon 3 would cost about 12.44¢ per mile (or about 18.66 for enough gas to drive approximately 150 miles).

Home charging costs can be offset by hosting your charger on a home charging sharing network. EV drivers can earn money by sharing their home chargers or connect with other hosts to find convenient charging on the go. For more information about how you can earn money by sharing your home charger, please see these popular sharing networks:

Public Charging CostsWhile charging at home is generally preferred, many people also charge their EV at public charging stations. These stations can be free, pay–as–you–go or subscription-based, and are set by networks or property owners. Some vehicle manufacturers, such as Hyundai, Nissan and Tesla also provide complimentary public charging.

One popular public charging network charges members 1.50 per hour to charge on Level 2, and 26¢ per minute for DC fast charging in California. 4 At these rates, charging a 40–kWh battery with a 150–mile range would cost about 8¢ per mile on Level 2, and 9¢ per mile for DC fast charging.

For more information about public charging networks, here are some popular options available in California:

1 A list of utility providers is at https://www.energy.ca.gov/almanac/electricity_data/utilities.html2 https://www.eia.gov/electricity/state3 https://www.energy.gov/articles/egallon-how-much-cheaper-it-drive-electricity4 https://www.evgo.com/charging-plans/

Charging Station Rebates

Rebates for Residential Level 2 Charging StationsMany California utility providers and air districts offer rebates to make home Level 2 charging stations more affordable. Some of the rebates also help to offset the cost of installing the charging station at your home if additional electrical work is required. Find available rebates where you live.

Rebates for Commercial EV Charging StationsProperty owners can take advantage of rebates for installing commercial charging stations for public use. EV charging is a desired amenity for many California drivers and can attract more traffic to your business, improve tenant or employee satisfaction and generate a new revenue stream (fees for charging). Following are incentives that decrease the cost of charger purchases and installation. Visit the websites for more information on program eligibility requirements and funding availability.

Utility Incentives

Air District Incentives

EV Charger Tax Credit 2023: What You Need to Know

The federal EV charger tax credit for electric vehicle charging stations and equipment is back for 2023 with a few key changes.

The EV charger tax credit is back, thanks to the Inflation Reduction Act (IRA) — massive climate, energy, tax, and healthcare legislation passed last year. You may have heard that the IRA contains billions of dollars in tax incentives including a tax credit for new and used electric vehicles. But the IRA also brought back the EV charger federal tax credit for electric vehicle charging stations and equipment that had expired two years ago.

There are some changes to the EV charger federal tax credit that you will want to be aware of so that you can potentially take advantage of the tax break. Here’s what you need to know.

23 EV Charger Tax Credit: Is an Electric Car Charger Tax Dedutible?

The federal tax credit for electric vehicle chargers originally expired at the end of 2021. However, the Inflation Reduction Act’s Alternative Fuel Refueling Property tax credit extends the EV charger tax incentive for ten years — through December 31, 2032.

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So, what does that mean for you? Essentially, if you install a home EV charging station, the tax credit is 30% of the cost of hardware and installation, up to 1,000. Also, beginning this year (i.e., 2023), the EV charger tax credit for business and home installations applies to other EV charger equipment like bidirectional (i.e., two-way) chargers.

Businesses that install new EV chargers or EV charger equipment can also benefit from a tax incentive of up to 30% of the total cost of equipment and installation. But they will have to meet certain labor and construction requirements to be eligible to claim the full incentive.

Before the Inflation Reduction Act, the limit on the amount of the EV charger tax credit for businesses was 30,000. That limit applies to projects that were completed before the end of last year. However, under the IRA, if you complete the business installation project after 2022, the tax credit per property item is up to 100,000 per EV charger.

All of this means that while electric vehicle chargers are not entirely tax deductible, you might benefit, to some degree, from the tax incentives in the Inflation Reduction Act that apply for refueling property.

How to Claim the EV Charger Tax Credit: Form 8911

To claim the federal tax credit for your home EV charger, or other EV charging equipment, file Form 8911 with the IRS when you file your federal income tax return.

  • You will need your receipts that show the purchase price of the EV charger and any fees for installation of the charger.
  • You will also need to know your tax liability for the year that you’re claiming the credit. That’s because the EV charger tax credit is subtracted from any federal tax that you might owe on that year’s return.

Also, the EV charger tax credit isn’t refundable, so you won’t receive cash back as a result of claiming the credit.

Biden’s EV Charging Station Plan

President Biden announced a 900 billion electric vehicle charging station investment plan. The plan is to build 100 million EV charging stations in thirty-five states. The Biden administration has indicated that the approved investment will span 53,000 miles of national highway.

The massive investment in EV charging stations stems from the Bipartisan Infrastructure Law that the White House says, “invests 7.5 billion to build a national EV charger network so that charging EVs is predictable, reliable, and accessible.”

Home Solar and Home EV Chargers

In a related addition to the EV charger tax credit, the Inflation Reduction Act provides incentives for installation of home solar panels with the Residential Clean Energy tax credit. For home and residential solar product installations, the IRA allows a nonrefundable tax credit of up to 30% of the total cost.

That 30% tax credit is based on eligible expenses like solar panels, power cells, labor, permitting and developer fees, other necessary related solar equipment, batteries, and inspection costs.

The solar energy tax credit applies for the next ten years — through December 2032. And the tax credit is available for the year in which you complete the solar installation.

The home solar panel tax credit can be beneficial on its own, of course. But it also has potential positive implications for people interested in using solar panels to charge their electric vehicles. That’s because if you’re eligible for both home and residential solar tax breaks and the tax credit for EV chargers and equipment, you could reap the benefits of two significant clean energy tax incentives in the new law.

And if you’re even luckier, you could be one of the consumers who is eligible next year to claim the EV tax credit for new and used electric vehicles.

EV Charger State Rebates and Incentives

In addition to the federal tax credit for EV chargers and EV charging equipment, there are numerous state and regional incentives that you may be able to benefit from if you have a home EV charging station.

For example, some utility providers in California offer both residential and commercial EV charger rebates. These California EV charger rebate amounts can be as high as 1,000 in some districts. New York offers an EV tax credit rebate that can also help offset the purchase and installation costs of an EV charging station. New York has offered a rebate of up to 5,000.

These are just a couple of examples of state EV charger incentives, but keep in mind that because the availability, amount, terms, and conditions surrounding state EV charger incentive programs vary considerably. So, it’s important to check your state to understand how the incentives work in your area.

Additionally, the U.S. Department of Energy has a searchable database on its website that can help you find state tax credits and rebates that might help offset or lower the cost of your EV charger and EV charging equipment.

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Many electric vehicle chargers across the U.S. do not work properly, creating a significant challenge for the Biden administration’s agenda and a shift away from gasoline-powered cars.

Difficulties with EV fueling aren’t encountered everywhere. But they’re common in areas where the government is spending the most money and has staked its claim on improving the charging experience. | Justin Sullivan/Getty Images

Imagine living in a world where the gas station has trouble providing gasoline.

electric, vehicle, charging, overview, charger

Every few times a driver fills up, something goes haywire — the gas doesn’t flow, or it flows fast for a while and then slows to a trickle. Other times, the credit card payment is mysteriously rejected or the screen is blank.

If the consumer wants a helping hand, too bad. In this world, the gas station has no human, and the only option is a 1-800 number. The gas pumps are alone in the middle of a big parking lot.

Swap the word “gasoline” for “electricity,” and this is a realistic description of what happens every day at electric-vehicle charging stations across the United States. The high-tech, high-speed highway fueling system that America is building to power its EVs and replace the gas station is riddled with glitches that are proving difficult to stamp out.

Individually, they are hiccups, but collectively, their consequences could be profound.

“It adds to the non-EV driver’s view of the world that EV charging is painful,” said Bill Ferro, a software expert and founder of EVSession, an EV charger analytics firm. “People feeling that it’s a risk to buy an EV because the fast-charging infrastructure stinks is going to slow down EV adoption.”

The problems are experienced by those who use fast chargers on the go and who aren’t driving Teslas. Studies and innumerable anecdotes describe the strange stumbles they encounter: a blank screen, a broken plug, a credit card payment that fails, sessions that abort without warning, electric current that flows fast this moment and slowly the next.

Behind the snafus are a daunting set of structural problems. They are tied to the peculiar way that EV chargers have evolved, and the fact that wires and batteries are way more complicated than what happens at the gas station.

“It’s a harder problem than pumping fuel from one reservoir into another,” Ferro said.

The problems are persisting even as billions of dollars pour into the charging sector from the federal and state governments, network operators and automakers.

Several recent studies of the charging system have found discouraging results.

The Biden administration, for example, set standards for “uptime,” or the percentage of time a charger is operational. California is launching a major inquiry into how to improve the customer experience. Automaker Ford Motor Co. last year deployed its own squad of station auditors. The largest public network, Electrify America, is replacing a fifth of its stations with newer models.

But many of these actions work at the edges of a black hole.

No one can define what it means for an EV driver to have a satisfactory charging experience. No underlying data exists. As hundreds of thousands of Americans buy EVs and start traveling the highways, this lack of a yardstick means that no one is accountable. Without accountability, problems are likely to persist.

The concern for industry is that the swelling ranks of EV drivers will tell their friends that highway charging is a little buggy, a little annoying — just enough of a hindrance that those millions of friends hold off from going electric, while the planet steadily warms.

Government steps in

Difficulties with EV fueling aren’t encountered everywhere. But they’re common in areas where the government is spending the most money and has staked its claim on improving the charging experience.

Home charging generally goes off without a hitch. The same goes for other “slow,” or Level 2, chargers that are sprinkled at workplaces and in parking lots and fill the battery by sipping on electrons for hours.

The bugs are most common with fast chargers, known as direct-current fast chargers, or DCFC. These are the charging solution when a driver is on the go and needs to refill the battery in 15 or 30 minutes.

These super-outlets exist near highway stops, in urban cores and at suburban crossroads. Building a network of them is the top priority of the Biden administration as it spends 7.5 billion for EV-charging infrastructure that Congress approved in the bipartisan infrastructure law. The first funding round is intended to blanket the country with DCFC chargers at 50-mile intervals along major highways.

Besides just building the stations, the government’s goal has been to create high standards, including better customer satisfaction.

The Federal Highway Administration, which is administering the program, said it “intends to incentivize charging station operators to improve reliability not just for chargers purchased with [government] funds but for all charging stations in the country.”

The irony is that a reliable, national charging network with high customer satisfaction already exists. It’s called the Supercharger network, built and run by Tesla Inc.

Users and experts are in wide agreement that Tesla has generally solved the problems that dog other networks. Its drivers plug in, pay and charge with few fails. Superchargers were exclusively for Tesla drivers until last month, when Tesla started opening parts of the network to other EV models.

Tesla also pioneered and excels at other practices that competing networks struggle to match — and that gas stations can’t do at all.

For example, punch in a destination on the Tesla app or the dashboard screen, and you get a route of Superchargers to stop at, with reliable information on which plugs are working and whether or not they are currently occupied.

A prime reason for Tesla’s success, experts say, is that Tesla owns and controls the entire ecosystem and all of its data. It built the cars, runs the chargers and manages the payments. If something breaks at the station, it’s Tesla’s job to repair it. There’s zero doubt who’s responsible.

The reason other, non-Tesla networks are having such troubles is that the public charging system has a lot more actors. They include a panoply of automakers, charging network operators, route-finding tools and now the government.

None has stepped up to take Tesla’s level of responsibility, and it’s not clear anyone will.

“Who’s owning this experience for me?” said Matt Teske, the founder and CEO of Chargeway, a EV-network software platform, putting himself in the position of an EV driver. “The answer is no one.”

A product not for customers

One reason today’s charging stations don’t work very well is their strange evolution as a consumer product.

Like EVs themselves, charging stations first arrived on the roads not because customers sought them out, but because regulators required them.

In the early 2000s, the California Air Resources Board demanded that automakers sell EVs to participate in the state’s auto market. Charging stations followed a parallel path.

One of today’s leading networks, EVgo Inc., was born from a 2012 legal settlement between NRG Energy Inc. and the California Public Utility Commission to resolve the electricity-market power crisis of the early 2000s. Another, Electrify America, is an entity that automaker Volkswagen AG was forced to create in 2016 as a penalty for cheating on its diesel emissions.

Tasked with satisfying regulators — and not customers — these companies saved money with a particular set of solutions.

“It was treated like it was really simple,” Teske said.

The charging station wouldn’t work like a gas station, with an employee in a nearby kiosk. Instead, it would operate without human intervention, like an ATM or a vending machine, but one that sells high-voltage electricity instead of Cokes.

But, unlike the ATM or vending box, the charging station wouldn’t get the full customer treatment. It wouldn’t be located under an awning, or be particularly well-lit or observed by security cameras. Instead, the electric car would be treated more like, well, a car. Stations were sited out in the elements, in the middle or at the edges of a parking lots, far from watchful eyes and easy targets for vandals.

Finally, the early networks didn’t offer the option of paying by credit card, although Electrify America was required to. Charging networks preferred to avoid the fees and complexity of Visa or Mastercard. Rather, payments would go to the network directly through a membership card.

What goes wrong

In the early days, none of these decisions much mattered. Early EV buyers were true believers who shrugged off the inconvenience of a dark parking lot or a frustrating charging session.

But as EVs not called Tesla have started to sell in earnest, the cost-trimming decisions of yesteryear have contributed to today’s outbreak of snafus.

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A charging station, it turns out, is vastly more complicated and breakable than a vending machine.

“If you’re looking for a checklist of what could go wrong,” Teske said, “it’s a long list.”

Inside the kiosk’s metal shell sit sophisticated power electronics. It sends dangerous levels of electric current through a heavy-duty cable and to a connector, which can be easily disabled with a wad of gum. The video screen — crucial for communicating information to the driver, like the and how long a charging session will last — can be defaced or broken. Any number of problems can befall a driver trying to tap, insert or swipe a payment card.

And then there’s the computer code.

“It’s all software, at the end of the day,” said Ken Tennyson, the director of quality and conformance at Electrify America, which has 800 or so stations around the United States.

The recipient of the cash from an ATM or the Snickers from a vending machine is a human hand. The recipient of the electrons from a charging session is an electric vehicle — or better put, an ever-changing, ever-widening array of electric vehicles, each of which communicates with the charging station with its own version of software.

While software protocols exist for the charging industry, “adherence to those standards is not perfect, and the standards themselves are not perfect,” Tennyson said.

Some of these software problems are the growing pains that come with any young and high-tech industry that hasn’t worked out the kinks. This one, however, is complicated by the sheer number of systems involved.

A satisfying charging session is an orchestra. The charging station, the network operator, the vehicle and the payments all work together seamlessly. But today, the orchestra is out of tune.

These disjunctions create problems that to the driver are inexplicable.

For example, the kilowatts delivered at any particular moment during a charging session — the rough equivalent of the amount of gasoline tumbling out of a pump — can fluctuate up and down without explanation. This is often due to faulty communication between the station’s electronics and the car’s, as they try to speak the same software language but fail.

All these handoffs also make it hard for networks to emulate Tesla’s navigational prowess. Tesla competitors, like General Motors Co.’s Bolt or Ford’s Lightning F-150, might be able to tell you that the next station is working and has room — or it might not. Software incompatibility makes things janky.

“It’s hard because people are bundling all the pieces together and there’s not one owner of the process,” said Ferro of EVSession.

A solution, of sorts

To improve reliability amid this confusion, industry and governments have turned to a measurement of dubious value.

That metric is uptime. Applied to machinery or systems, uptime is a simple measurement. It is the amount of time in a given period that a machine is operational, stated as a percentage.

Uptime is a binary. A machine is either up, or it’s down. A charging station is considered “up” if its operator pings it and gets a positive response. But that narrow definition can collapse with an experience as complex as charging.

Uptime “doesn’t measure whether the connector is broken, or there’s payment-processing issues, or the parking space is ICE’d,” said Loren McDonald, an independent EV-charging analyst. ICE refers to a EV-charging parking space being occupied by an internal-combustion engine vehicle, another bane of EV drivers.

The metric fails, McDonald added, because it doesn’t answer the key question: “Can I charge or not?”

“Uptime doesn’t capture that,” he said.

Nonetheless, uptime has become the foundation on which federal and state governments are measuring performance as they dole out billions of public dollars.

For example, the Biden administration decreed last year that charging stations receiving federal money from the bipartisan infrastructure law must achieve better than 97 percent uptime.

It’s not alone in that target range. Colorado, New York and Vermont have adopted a 97 percent standard for their charger funding, while the state of Maine has adopted a lower 95 percent. Some electric utilities, like Louisville Gas Electric in Kentucky and Consolidated Edison in New York, have aimed for as high as 99 percent.

Narrow as it is, the federal standard is at least a start. “It’s really helpful to have that federal guidance out there,” said Jesse Way, a clean transportation policy advisor at Nescaum, a nonprofit association of air-quality agencies in the Northeast.

Whether a 97 percent uptime is rigorous or not depends on whom you ask.

Tennyson of Electrify America considers it quite rigorous because it leaves a charging station with little room for error. A breakdown requires repairs that can consume days. In a year, he said, “You don’t have a tolerance for more than two or three failures.”

The reverse is argued by McDonald, the EV analyst. He points out that 97 percent uptime means three percent downtime. In the course of a year, that’s downtime of 11 days.

“Which is a really low bar if you ask me,” he said. “Could you imagine Amazon Web Services” — Amazon.com Inc.’s Cloud product for businesses — “being down 11 days a year?”

A data void

One reason the Biden administration may have seized the narrow solution of uptime to solve the broad problems of EV-charger reliability is that no other options exist.

“The uptime calculation does not address all categories of failure or ways that chargers may fail to provide a satisfying customer experience,” the Federal Highway Administration conceded in guidance it released to states earlier this year.

Why not do better? “Insufficient data are available,” FHWA said.

That lack of data is a key gap, experts say. No independent, third-party source of charging data exists in the U.S. today. If a charging network claims to achieve 97 percent uptime — and many do — there’s no way to check out the claim.

That’s a worry for states that are entrusted with spending millions of dollars of federal money to build charging networks. The feds require them to achieve 97 percent uptime. But Teske, of the company Chargeway, pointed out that states who are vetting the companies to build those networks are “taking the sellers at their word.”

Solutions may be coming, but they will take time.

As part of the bipartisan infrastructure bill, the Biden administration gained the authority to gather data from the charging stations it funds. States are required to start sending data along a year from now. That information will, FHWA says, become “a national database and analytics platform” with “a public-facing dashboard.”

A major structural solution may be in the works in California.

Last year, California lawmakers passed a bill that requires new record-keeping and reporting standards for charging stations that get state money. The rules, to be drafted by the California Energy Commission, are due by 2024. They could eventually be copied by the numerous of states that align themselves with California’s transportation emissions policies.

“It’s very complicated, we don’t have all the answers,” said Patty Monahan, a CEC commissioner, at a Bloomberg New Energy Finance conference earlier this year. “This is a huge inquiry.”

In the meantime, the gritted teeth of those using highway fast chargers are unlikely to relax anytime soon. The next wave of EV adoption will, in part, continue to be a story of inert plugs and frowning drivers, posted on Instagram for all to see.

“I see this is a problem for the next five years,” said Ferro, the EV charging expert. “Either Tesla will take over the entire charging network of the U.S., or everyone else will get their act together, or a little bit of both.”

A version of this report first ran in EE News’ Energywire. Get access to more comprehensive and in-depth reporting on the energy transition, natural resources, climate change and more in EE News.

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