Residential Energy Use by Time-of-Day and the Duration of Charging Sessions. (Note: Time is active charging time only.)

Residential Energy Use by Time-of-Day and the Duration of Charging Sessions. (Note: Time is active charging time only.)

The US Department of Energy (DOE) published a new report on electric car charging presenting customer behaviors and impact on the grid.

Data comes from different projects made by six utilities:

  • Burbank Water and Power (BWP)
  • Duke Energy (Duke)
  • Indianapolis Power & Light Company (IPL)
  • Madison Gas and Electric (MGE)
  • Progress Energy (now part of Duke Energy as a result of a merger in 2012)
  • Sacramento Municipal Utility District (SMUD)
In total, over 270 public and over 700 residential charging stations were evaluated.

According to the report, the electric power industry expects a 400% growth in annual sales of plug-in electric vehicles by 2023, so not strange that utilities are interested to learn something onhow to take advantage of electric cars and not end up with a black out.

For now, the impact of electric car charging on the electric grid is negligible due to the low number of plug-in vehicles, however typical load curves already can be determined, as well as finding that only a few percent of charging sessions are longer than 4 hours (and 12 kWh). It should be easy then to encourage EV owners to charge off-peak during the night.

Major Findings

"There are relatively few plug-in electric vehicles on the road today; as a result the six SGIG projects focused on establishing the charging infrastructure with a relatively low number of stations and evaluated a small number of participating vehicles. As expected, project results showed negligible grid impacts from small-scale electric vehicle charging today, but gave utilities important insights into the demand growth and peak-period charging habits they can anticipate if electric vehicle adoption rises as expected over the next decade. Utilities face a challenge in determining when their customers purchase electric vehicles, and where and when they will plug-in to satisfy charging needs."

"Given the current rate of customer electric vehicle adoption, utilities are considering plans for electric vehicle charging programs. For example, BWP analysis showed that with a 25% per year growth in usage at public charging stations, utility investments could have a seven-year payback, which would be a financially attractive business case for some utilities. Table 1 provides a summary of the key project experiences from the six projects."

Table 1. Summary of Key Project Experiences

Table 1. Summary of Key Project Experiences

Full report can be found here: "Evaluating Electric Vehicle Charging Impacts and Customer Charging Behaviors: Experiences from Six Smart Grid Investment Grant Projects"