Longer range electric vehicles and more powerful chargers could be a “boon to utilities” technically, environmentally, and financially, but will require utilities to adopt strategies for optimizing residential EV charging, according to a new report from research firm Pecan Street.
The premise of the report, Charging Smart, is that an increase in the maximum power level of residential electric vehicle (EV) chargers is imminent and will likely reach the highest charger levels within a decade, leading to increased costs for utilities by shifting charging load to times of day when electricity is more expensive.
Today, most electric vehicles charge at below 10 kilowatts (kW) of power, but Pecan Street’s researchers expect power levels to increase. The practical upper limit of power for residential charging is a function of the electrical service to the home. For a home with 200 to 300 ampere service, the maximum charge level is likely to peak around 18 kW, they said.
Higher capacity electric vehicles and chargers creates “significant electricity demand” and “fundamentally changes a home’s energy demand profile,” the report found. “If charging takes place at scale across a utility’s territory during times of peak demand, it will contribute significantly to higher peak demand with rapid ramp rates.” However, because high-capacity chargers are more time-efficient, “they offer more flexibility to shift EV charging to off-peak times while still allowing for vehicles to be sufficiently charged,” the authors said. The authors noted that several vehicles in their sample already have charger power levels in the 16-kW to 18-kW range.
The sample consisted of 92 homes, most within the Electric Reliability Council of Texas (ERCOT) region. The report included data from 2018 and 2019 but excluded 2020 data because of the COVID-19 pandemic, which changed driving patterns.
More powerful electric vehicle chargers could add more load to peak summer demand and increase the cost of summer charging by 8 percent, but shifting that load could have a large impact, the report said.
Moving 35 percent of residential charging load (by kilowatt hour) leads to a 59 percent wholesale electric cost differential between the highest and lowest scenario outcomes during the summer season, the report found.
The report looked at four scenarios:
- An upgrade to maximum power chargers with no shift in charging time;
- An upgrade to maximum power chargers with charging shifted from 9 p.m. – 5 a.m. to 5 p.m. – 9 p.m.;
- An upgrade to maximum power chargers with charging shifted from 11 a.m. – 8 p.m. to midnight – 4 a.m., and
- An upgrade to maximum power chargers with charging shifted from cycles that begin when the ERCOT prices are high to midnight to 4 a.m. time frame.
Pecan Street’s analysis of the scenarios found that a post commute charging trend would “significantly increase utility costs” but that both scenarios in which electric vehicle charging is shifted to overnight hours “reduced overall EV charging cost in every model run.”
“The findings show an 18 percent cost increase for the worst-case scenario and a 23 percent cost decrease for the best-case scenario,” the report’s authors said. The best case scenario shifted a percentage of electric vehicle charging from peak times to overnight. The worst case scenario had more electric vehicle owners charging in the early evening.
The authors recommended that utilities should explore time variant rate options, as well as hybrid pricing options that offer higher fixed rates from 6am to midnight and discounted fixed rates from midnight to 6am. Utilities should also consider incentives for the deployment of smart charging technologies, such as owner-operated programmable charging systems and direct charge control functions in conjunction with pricing signals. And, finally, the authors say utilities should establish outreach campaigns to influence customer behaviors to shift charging patterns.
“What’s so promising about this analysis is the clear opportunity to push innovation that will use vehicle electrification to create a more reliable electric grid and maximize greenhouse gas reductions,” Suzanne Russo, Pecan Street CEO, said in a statement. “It’s critical that utilities and regulators act now to establish programs that encourage the adoption of smart charging technology and optimal charging behaviors.”
Austin, Texas-based Pecan Energy worked with Austin Energy to test the use of EVs as peak shaving tools and, eventually, as a grid resource. The tests, which were conducted at Pecan Street’s laboratory in east Austin, involves the use of an EV capable of bi-directional energy flows, also known as V2G capability.
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