By Mark Jones
My wife, Erin, is now the proud owner of a plug-in hybrid vehicle. It is a purchase intended to make us more sustainable. Like previous purchases intended to reduce our environmental impact, it does not make economic sense.
It is not our first hybrid. It is our first lithium-ion battery vehicle, fitting since both of us spent part of our careers developing better lithium-ion batteries. We both spent large chunks of time focused on sustainability. We actually try to live more sustainably and consider sustainability when making decisions.
Erin wrestled with going full electric but found the plug-in hybrid a more compelling choice. The car has a 40-mile range on full EV. That more than suffices most days. Her average is fewer than 10 miles per day. The 18-kWh battery is more than sufficient for typical use. Visiting our daughter is a common road trip and could not be done on a single EV charge. Going full EV would require a significant change in driving habits. Additionally, my studies during my working career pointed toward limitations around battery supply. At the macro level, having more vehicles with 40 miles of full EV are a better allocation of limited batteries than fewer vehicles with longer range. On both counts, the plug-in option, backstopped by gasoline, is the best compromise for our household and the planet. Most days, driving uses only electric power. On those days, it is as good as an EV for the planet. On longer trips, we’re still far more efficient than the internal combustion version of the same car.
The plug-in hybrid provides continuous feedback on efficiency. It makes driving a game where trying to maximize efficiency is the goal. Driving more efficiently is directionally correct for sustainability but doesn’t tell the full story. It doesn’t tell me whether my GHG emissions are less, whether money is being saved, or even whether time is saved. Instantaneous efficiency makes for a fun game, but emissions, money, and time are what I ultimately care about.
The plug-in hybrid joining our household was noticeable. Our electricity use increased by 1.5 times. That was about what I was expecting. For many, per-person car and home energy use are about equal. Crunching the numbers showed that the delivered cost of the electricity per mile was slightly higher than operation on gasoline at current prices.
Emissions are reduced when using only electricity, but only by about 20%. I was certainly hoping for more. Buying even more renewable energy will make it better, but at an additional cost. Based on actual usage, that 20% equates to about 800 pounds of GHG emissions avoided every year. The difference in sticker price between the PHEV and HEV was about $10,000, or about $2500/ton CO2 avoided over a 10-year life. That is about 10-100X the normally quoted abatement costs. The PHEV is reducing GHG emissions, but at a high cost.
Time is saved. Plugging takes seconds and avoids the gas station. Erin will save about 12 hours a year, 120 hours over an assumed 10-year life. That works out to $80/hour. So time is saved, but likely at a high cost.
We considered sustainability when making a car purchase. It wasn’t a decision made purely on economics. Had cost-saving been our goal, our more sustainable choice would have missed the mark.
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Filed Under: Commentaries • insights • Technical thinking
