Study: PHEVs may be greener than pure EVs

plug-in-priusAre plug-in hybrids generally more environmentally friendly and economically efficient to produce than pure EVs?

They may be according to a study conducted by Carnegie Mellon University and summarized recently by Edmunds Auto Observer.

According to the CMU researchers, EVs with larger battery packs may actually produce more emissions than those with smaller packs — depending on where and when the vehicles are plugged in.

Bigger battery pack = higher costs
“Although the lifetime costs of conventional, HEV, and PHEV20 are comparable, it is clear that the high costs of vehicles with larger battery packs are not balanced by fuel cost savings or emissions damage and oil premium reduction,” the report noted.

Considering such factors as costs for health care, environmental damages and oil consumption, the CMU researchers ultimately concluded that, generally speaking, the best type of EV on the market right now is one with a small battery pack, such as the 2012 Toyota Prius Plug-in or the 2012 Nissan Leaf.

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“Because vehicles with larger battery packs are more expensive, fewer of them can be subsidized, and that can result in lower total benefits,” Jeremy Michalek, one of the study’s authors notes.

Future may be different
Study co-author Mikhail Chester added that vehicles with larger battery packs might eventually be equally as beneficial as the ones with smaller battery packs.

“It’s possible that in the future plug-in vehicles with large battery packs might offer the largest benefits at competitive costs if the right factors fall into place, including sufficiently low cost batteries, high gasoline prices, low emission electricity and long battery life,” Chester said. “But such a future is not certain, and in the near term, hybrids and plug-in vehicles with small battery packs provide more emissions benefits and oil displacement benefits per dollar spent.”

Overall, reports Edmunds, the researchers hope that the study will help developers, government officials and others to understand the tradeoffs in terms of producing different types of EVs.

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