Electric vehicles expected to have little impact on transmission system

While recent reports suggest that incorporation of electric vehicles (EVs) could strain the distribution system in some areas of the country, the ISO/RTO Council (IRC) said EVs should not cause a problem for North America’s transmission system.

”We don’t expect plug-in electric vehicles to significantly affect load on the bulk power grid in the near future, in part due to the gradual rollout of electric vehicles,” a spokesperson for the ISO/RTO Council, an organization of the independent system operators and regional transmission organizations in North America, told TransmissionHub. “An electric car recharging equals the load of four or five plasma TV sets, so overall demand will not be notably affected in small numbers.”

Just as people of similar incomes and mindsets tend to group together in neighborhoods, electric vehicles can also tend to be purchased in geographic clusters.  Analyses by companies including IBM and BusinessInsider indicated that such clusters could place a strain on the distribution system in the vicinity of the clusters.

Consider that a 120-volt charger for the all-electric Nissan Leaf draws approximately 3.3 kW. The EPA website said charging an EV enough to drive 35 miles would take about 10 hours, or about 33 kWh. Therefore, charging an EV sufficiently to drive 35 miles per day, five days a week would increase a household’s monthly electric use by approximately 660 kWh. Multiplying that demand by the number of EVs in a given cluster would provide an indication of the added impact on the area’s distribution.

The IRC studied EVs and their potential impact on the electrical grid and found that one million EVs could be on U.S. roadways by 2020. To incorporate those vehicles smoothly, the IRC developed recommendations.

“One unified recommendation from the study was to encourage utilities and retailers to offer incentives for smart charging, such as overnight/off-peak charging,” the spokesperson said.

The study also identified some advantages EVs could bring to the transmission system.

”For us as grid operators, electric vehicles represent a new opportunity to provide ancillary services and use power system assets more efficiently,” the spokesperson said. “If widely deployed in the right way, electric vehicles can enhance efficiency of the grid by shifting load to off-peak nighttime hours.”

Other studies support the conclusions of the IRC study.

A 2008 study by the Oak Ridge National Laboratory for the U.S. Department of Energy indicated that the effect of even a significant expansion in electric vehicles could be minimal.

While electric vehicles are expected to account for around one quarter of the market by 2030, their impact on the transmission system would be minimal if the vehicles are charged after 10 p.m., when electricity demand is low, according to the Oak Ridge study. In that case, the study indicated the transmission system would be adequate and no additional power generation would be required.

However, that study cautions that the expectation does not consider that “drivers will control the timing of recharging, and their inclination will be to plug in when convenient, rather than when utilities would prefer.”

If drivers begin charging their vehicles at 5 p.m. instead of 10 p.m., “Most regions will need to build additional capacity or utilize demand response to meet the added demand,” the study said, especially by 2030 when EVs “have a larger share of the installed vehicle base and make a larger demand on the system.”