SDG&E; study: Plug-in Hybrids Offer Significant Improvements in Gas Mileage and Reductions in Emissions

sdge plug-in hybrid prius photo

Photo: SDGE, Darin Fong
Real-World Testing of Plug-in Hybrids
San Diego's SDG&E; utility is now two years into its study of plug-in hybrids (phase III), and it has released some of what it found out. It's generally positive stuff, though not quite mind-blowing. The way they did it is that they first gathered data on regular hybrids and then converted them to plug-in hybrids (with 5kWh lithium-ion batteries) while keeping the same drivers and usage patterns. How did the plug-ins compare? Read on to find out.SDG&E; writes:

When compared with the standard hybrid, the plug-in hybrid at 68 miles per gallon (MPG), achieved a 58-percent increase in gas mileage, a 37-percent decrease in carbon dioxide (CO2) tailpipe emissions, and a 10-percent reduction in fuel costs. When compared with a conventional gasoline-fueled vehicle that averages 22 MPG, the plug-in hybrid achieved a 68-percent reduction in tailpipe emissions and a 54-percent reduction in overall fuel costs.

Those numbers look a bit weird to me. A 58% gas mileage increase sounds like it should reduce fuel costs by more than 10% even if electricity is expensive.

But the really interesting part of the report is this: "Today, California’s electricity capacity could recharge as many as 4 million plug-in hybrids when charged during off-peak hours when electricity use is low."

This is important to understand, because many people think that electric cars automatically mean that we'll need to build more power plants. As other studies have shown (including one by the Oak Ridge Lab that concluded that "Plasma TVs, industry officials say, consume about four times the electricity as recharging a plug-in hybrid."), that's not necessarily the case.

On their own, most people would probably recharge their EV at night, and with a smart grid, it would be easy to better manage and coordinate charging so that spare capacity is used first (which would also be good for drivers since - if there's a time-of-use rate - they would charge up when electricity is cheaper). We're talking big money:

The plug-in hybrid’s fuel-cost savings over traditional gasoline-powered vehicles would save these 4 million consumers approximately $4.2 billion a year at today’s average gasoline price of $3 per gallon when compared to 15 cents per kilowatt-hour of electricity for 14,400 miles driven annually.

Via SDG&E;, Green Car Congress
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