Electric Vehicles

Study examines charging habits of electric vehicle owners

An initial analysis of a study being conducted by Arizona public power utility Salt River Project and the Electric Power Research Institute has found that time-of-use price plans have been effective at incentivizing electric vehicle owners to charge later than they normally would.

SRP said Jan. 11 it is one of the first utilities to study the charging habits of EV drivers. The Tempe, Arizona-based utility wants to know how the increase in energy consumption from EVs will affect the grid.

A hundred SRP customers volunteered to have data loggers installed on their vehicles to collect charging information such as time, duration and location.

“We wanted to see where and how EVs will impact our system,” said Kelly Barr, SRP senior director of environmental management and chief sustainability and compliance executive. “We also wanted to learn how our customers with electric vehicles selected and utilized our pricing options to determine which price plan worked best for them.”

In an initial analysis, SRP estimates that the roughly 4,400 EVs in the utility’s service territory use more than 9,121 megawatt hours a year. At SRP’s system peak at about 5 p.m., these vehicles also use more than one megawatt of electricity.

The study found that time-of-use price plans have been effective at incentivizing EV owners to charge later than they normally would, which will help SRP meet customer demand without needing to add power plants.

As “early adopters,” current EV owners tend to know they can use TOU rates to lower their charging costs, according to SRP. The utility intends to educate future EV owners on the benefits of TOU programs so they avoid charging during peak times.

SRP offers several TOU plans, including one geared for EV owners that offers up to 10,000 customers a “super” off-peak period every day from 11 p.m. to 5 a.m. During the program’s summer peak, which covers July and August, EV owners pay 6.3 cents per kilowatt hour to charge their car during the late-night hours compared with 22.26 cents/kWh from the 1 p.m. to 8 p.m. peak period.

SRP said it decided to conduct its own study because Arizona drivers and climate are different than other parts of the country.

The study began in June 2016 and is expected to end this year.

SRP will conduct a second study later this year with some of the newer EVs that have a battery range of more than 200 miles, such as the Chevy Bolt and Tesla Model 3.

More than 32 EV models, with expanded ranges, are coming to market between 2017 and 2019, according to EPRI.

“There soon will be an affordable, electric equivalent to every conventional vehicle currently on the market,” said Jamie Dunckley, EPRI data scientist for electric transportation. “Understanding when, where and how much people charge is fundamental to be able to plan for and serve these customers effectively.”

EV sales in the United States have grown by 32 percent a year on average from 2012 to 2016, according to EPRI.

Almost 200,000 plug-in vehicles were sold last year, according to Inside EVs, a website focused on electric vehicle news.

Looking ahead, Bloomberg New Energy Finance expects EV sales to account for about 3.5 percent of all new U.S. car sales in 2021, up from about 2 percent this year, according to an annual report on the EV market released in July.

EV sales will make up about 10 percent of new car sales by 2025 and grow to about 35 percent of all sales by 2030, according to the research firm.

EVs will be price competitive with internal combustion engine vehicles on an unsubsidized basis around 2025, when sales are expected to take off, the report said.

“The ‘peakiness’ of fast-charging load profiles will need to be managed by utilities and regulators through the introduction of time-of-use rates to encourage off-peak charging, as well as storage solutions at the operator site which can mitigate high power demand from the grid,” the report said.