Enexis: smart charging of electric cars leads to 40 percent less peak load

The peak load of charging electric cars at home can be reduced by about 40 percent, if chargers support smart charging. This would allow more electric cars to be charged at home without overloading the grid.

For the ‘Flexible charging behind the meter’ study, grid operator Enexis provided 138 households with an energy management system that regulates the energy flows within a house. Enexis feeds this EMS with information about the available grid capacity, enabling the EMS to regulate the charging speed of an electric car. For example, the EMS can ‘considerably’ reduce the charging speed during peak hours between 17:00 and 21:00, and then increase this speed again during the night. For the pilot, Enexis worked with a lower charging speed limit of 6A.

The test shows that charge control via EMS reduces peak load by 40 percent. In theory, however, higher percentages are possible, because the loading time can be moved completely outside peak hours. According to Enexis, the vast majority of participants are positive about smart charging. For example, 84 percent indicated that they would like to use this in the future and 81 percent would recommend it to other electric drivers.

The pilot lasted from September 2017 to September 2019, with participants participating for a year. Participants were divided into four groups. Two groups were given a static charging profile, in which charging was always reduced between 5 pm and 10 pm. The other two profiles were given a dynamic charging profile, in which the capacity of the electricity grid was leading. When too many electric cars wanted energy at the same, busy moment, the charging speed was temporarily reduced.

With the static profile, Enexis saw no reduction in the peak load, because the electric cars immediately started charging at 10 p.m. The peak load was thus only shifted in time and not reduced. According to Enexis, there was a reduction in the peak load with the dynamic profile, namely the aforementioned 40 percent.

Users were also given a flex button during the study, which they could use to charge the car at normal speed for 24 hours if desired. When users did this no more than twice a month, they received a reward of fifty euros after the year. Those who used the flex button more than twice in a month received one euro less each time as a reward. According to Enexis, this button was hardly used, but it did play a major role in the acceptance of charge control. A number of participants would see this button as a necessary condition for participation in charge control. Of the users, 23 percent indicated that they took the reward into account when using or not using the flex button.

Finally, 52 percent of the participants indicated that they noticed the application of charge control. The participants indicated that their car charged more slowly; some indicated that their car was charged less than usual. These participants therefore used the flex button, or charged at a fast charger or at their destination. Energy managers previously said that smart charging of electric cars is important for the affordability and reliability of the energy grid.