CLEAN TECH: Metering Electric Vehicles

By Published On: September 3, 2010

Later this year, General Motors plans to deliver its first plug-in hybrid electric vehicle, the Chevrolet Volt, to customers. Those who lease the Volt get an electric charging device to install in their homes to fill up the vehicle’s batteries. The Volt--which can travel 40 miles on an electric charge before using an onboard gasoline engine for longer trips--presses the question of whether the grid is ready for the extra load that electric vehicles present. As the California Public Utilities Commission and utilities prepare for the coming onslaught of plug-in hybrids and pure electric vehicles--like the Nissan Leaf slated for delivery late next year--one of the key questions is how to meter the vehicle chargers installed in homes. At issue is a dynamic tension between hindering the early acceptance of the new electric vehicles versus making the long-run preparations to optimally integrate battery-powered vehicles into the grid. Grappling with the dilemma, CPUC staff issued a white paper on metering electric vehicles August 30. It outlines alternative approaches and makes both short- and long-term recommendations. From the grid’s point of view, the white paper notes, it would be optimal to meter household vehicle chargers directly by installing separate meters that carefully measure their draw on the power system. Metering the chargers separately would allow utilities to bill motorists under a specially designed electric vehicle tariff that could incentivize charging at off-peak hours to prevent straining the grid. If the separate meters were equipped with communications capabilities, chargers could be included in utility demand-response programs and be temporarily turned off during periods of peak demand. Separate metering would allow utilities to easily earn credits under the state’s low-carbon fuel standard, which seeks to cut greenhouse gas emissions from transportation fuels 10 percent over the next decade. The paper also points to a sub-metering arrangement, which would function similarly to separate metering though be a bit less expensive to implement. Even then, any separate meter drives up the price and lengthens the time it takes to install household chargers that come with electric vehicles. Already, according to the CPUC, it costs an average of about $1,500 to install a charger, including wiring and upgrades to the household circuit breaker panel. It also takes 45 days to process all the paperwork before performing the actual four-hour installation job. Installing a separate meter could add anywhere from another $150 to $1,000, depending upon the complexity of the meter and its communications capabilities, plus an unknown amount of time because utilities would have to become involved in installation. The paper further notes that the new meters could become “stranded assets.” This could occur, for instance, if a motorist decided to go back to a conventional gasoline-powered car after using their electric vehicle for a while. There are many other complications raised in the paper too. Until they are sorted out, the CPUC recommends that over the next one to three years chargers be installed without any additional meter in homes. The paper further recommends that charger installers notify utilities of the presence of new electric vehicles in neighborhoods so they can make sure their local distribution system can handle the new load, which can be equivalent to a whole house. After three years, the paper recommends that utilities develop tariffs for all three metering alternatives--single metering, separate metering, and sub-metering--and that all of these options be available to electric vehicle purchasers.

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