December, 2014″ Six utilities that participated in DOE’s cost-shared Smart Grid Investment Grant (SGIG) program deployed in-home and public electric vehicle charging stations and evaluated customer charging behaviors and impacts on the grid. There are relatively few plug-in electric vehicles on the road today, and 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.
Charging Behaviors: i. The vast majority of in-home charging participants charged their vehicles overnight during off-peak periods. Where offered, time-based rates were successful in encouraging greater off-peak charging. ii. Public charging station usage was low, but primarily took place during business hours and thus increased the overlap with typical peak periods. Plug-in hybrid owners frequently used the (often free) public stations for short charging sessions to “top off their tanks.”
Grid Impacts: iii. The length of charging sessions and the power required varies based on the vehicle model, charger type, and state of battery discharge. iv. The average power demand to charge most vehicles was 3-6 kilowatts, which is roughly equivalent to powering a small, residential air conditioning unit. v. However, depending on the model, the load from one electric vehicle model can be as much as 19 kilowatts, which is more than the load for most large, single-family homes.
Technology Issues: vi. Faster chargers may require more expertise to install in homes and public stations. Installing a 240-volt charging station, which typically charges 3-5 times as fast as a charger using a standard 120-volt outlet, requires a licensed electrician and occasionally service upgrades. vii. Public charging station installation had high costs and required substantial coordination with equipment vendors, installers, and host organizations to address construction, safety, and code requirements. viii. Low usage at public charging stations will require longer capital cost recovery without substantial growth in usage. ix. Some utilities found residential interoperability problems in communication between smart meters and charging stations. SMUD found that the two devices only connected successfully about 50% of the time during load reduction events.
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Advanced Metering Infrastructure: ($1,997,812,053 or 43% Federal Share) Advanced metering infrastructure (AMI) is a system of smart meters, two-way communications networks, and data management systems implemented to enable metering and other information exchange between utilities and their customers. In addition, a subset of SGIG projects are conducting statistically rigorous studies of consumer behavior and demand response. These projects include applications of AMI, time-based rate programs, and enabling technologies such as Web portals, in-home displays, and programmable communicating thermostats. They also include the use of randomized and controlled experimental designs with treatment and control groups. This effort presents an opportunity to advance the electric power industry’s understanding of consumer behavior through highly rigorous statistical methods.
