moves toward this greener power generation mix remains uncertain.
An alternative set of scenarios for U.S. power generation was developed jointly by the Electric Power Research Institute (EPRI) and the Natural Resources Defense Council (NRDC) to explore the relationship between the grid and PHEVs if it becomes necessary to lower CO2 emissions from U.S. electric power generation (EPRI/NRDC, 2007). Nine modeling scenarios were developed spanning high, medium, and low emissions of CO2 and low, medium, and high penetrations of the fleet by PHEVs. Chapter 4 compares greenhouse gas (GHG) emission intensities of the EIA Reference Case with the EPRI/NRDC medium case.
Among other things, EPRI and NRDC concluded that all nine cases showed significant GHG reductions attributable to PHEV fleet penetration. Cumulative GHG savings from 2010 to 2050 could be significant, ranging from 3.4 to 10.3 billion MT of CO2.4
Recognizing that reductions of this magnitude are not likely to occur without public policy intervention, the committee used the EPRI/NRDC results to illustrate the potential benefits that PHEVs might provide under a policy-driven low-emission grid scenario.
If a dedicated circuit is not required, many PHEVs can be charged with little or no change to an owner’s electrical service. Although significant upgrades in the electrical distribution system might be required for a large PHEV population, utility planners should have sufficient time to prepare for these changes.
Charging a PHEV may be a simple matter of finding a suitable electrical outlet (most likely in a home garage) and plugging in. In other cases, however, it will be more complicated. The time required to charge a PHEV at regular household voltage may be quite long, so a voltage upgrade may be necessary. Zoning codes or standards may require upgraded or dedicated service for PHEVs, and PHEV-friendly, off-peak charging may require the installation of dedicated charging circuits and/or meters.
One recent study considered three levels for PHEV charging (Morrow et al., 2008):
Level 1 charging uses a standard 110 volt, 15 to 20 ampere circuit, standard in residential and commercial buildings. Level 1 provides relatively little power and may necessitate prolonged charge times.
Level 2 charging involves a 220 volt, single-phase, 40 ampere circuit. At the higher voltages and currents, charging would be more rapid, but Level 2 service is not common in residential garages and would generally entail a system upgrade.
Level 3 charging uses a 440 volt, three-phase circuit supplying 60-150 kW of power and can deliver a 50 percent charge in 10-15 minutes, depending on vehicle size and electrical range. Level 3 charging might be the choice for public garages, parking lots, and shopping centers.
The committee has considered charging only at Levels 1 and 2, believing that charging at Level 3 will not become important until much later. Table 3.1 provides estimated charging times for representative PHEVs and charging stations. Costs per charging station were estimated (numbers rounded by the committee) as follows (Morrow et al., 2008):
Residential garage charging
Level 1, $880
Level 2, $2,100
Apartment complex charging
Level 1, $830
Level 2, $1,500
Commercial facility charging
Level 2, $1,900
At the time this report was prepared, manufacturers had not announced whether they would equip PHEVs for charging at both 110 and 220 volts. The committee believes, however, that the additional cost for dual voltage vehicle charging is probably small and not likely to significantly affect the committee’s analysis.
In summary, some PHEV owners may be able to charge their vehicles using their existing home electrical service, but many others probably will not. The cost of upgrading