$25. 002009 ieee 52 ieee

56 

IEEE

 

power & energy magazine

 

march/april 2009

“light-duty fl eet.” What’s more, switching from gas-only vehi-

cles to mostly plug-in vehicles could reduce the importation of 

oil by up to 52%, according to the PNNL. 

“Proper or optimal” use of the power grid, however, may 

not be as simple as it sounds. Plug-in vehicles will represent 

a signifi cant new load on the existing primary and secondary 

distribution networks, with many of these circuits not having 

any spare capacity and no monitoring and automation capa-

bility. The additional charging load will typically be behind 

either an existing secondary distribution transformer in a 

residential neighborhood or a circuit/ transformer connected 

to a distribution feeder. A charge for 30–40 miles of driving 

will require 7–10 kWh of power, since most plug-in vehicles 

require 0.2–0.3 kWh of charging power for a mile of driving. 

This will add signifi cant load to the distribution network as 

the penetration level of PEVs increase.

Figure 3 provides a summary of some of the PHEV mod-

els that have been recently announced. They range in  battery 

 capacity from 16 kWh to 53 kWh. As can be seen, a full 

charge within a reasonable time—say, less than 3 to 4 hours— 

will require plugs with 6.6kW or 16 kW capacities. 

Figure 4 illustrates a typical household load with a plug-

in  vehicle  charging  load  of  1.4  kW  in  the  evening.  During 

its charging time, the plug-in vehicle more than doubles the 

average household load. Fast chargers, at 6.6 kW or higher, 

will signifi cantly alter the load pattern of the consumer.