The Challenge of Eco-Driving a Plug-in Prius
Editor’s Note: This post was originally published four years ago today. Eco-driving is a simple thing everyone can do whether they drive a Prius or not. Dig in for more details.
I love eco-driving in my 2012 Prius plug-in! It’s more fun than a video game, and when I “win,” so does the planet! Here’s my personal challenge. What is the highest miles per gallon I can achieve? Can I manage all my in-town driving with zero ghg emissions to the atmosphere? Read on to find out.
First, some background. I chose the plug-in Prius because the range on electric cars back in 2012 plus the lack of charging stations made me too nervous. Now with several models of electric vehicles getting 80 miles per charge, and apps that locate unoccupied charging stations plus terrific deals on leasing, electric vehicles look increasingly attractive!
But here I am with my plug-in that holds a charge of only 12 to 13.3 miles, depending on outside temperature, and then switches to an efficient gas engine. The car also has an extremely aerodynamic design that hugs the ground and drives best with the windows up and vents open above 45 mph.
What can I do to enhance the efficiency of my plug-in Prius with my driving habits and choices? Lots!
Living here in Davis, my first choice is whether to drive at all. I keep the car covered in the driveway which encourages me to choose my bicycle first. After all, on a bike I get exercise, fresh air, a chance to enjoy being out-of-doors, and door-to-door service with no parking issues. The whole city is only 6 miles long, so nothing is out of reach in this bicycle-friendly town.
But of course there are the times I need more than three baskets of groceries, or I’m loaded up for a Cool Davis event or it’s just too late, dark, windy, cold or unappealing to bike. The Prius allows me to drive guilt-free! As long as I am always careful to keep the car charged up, I can plan my route for a series of errands and the 12+ miles of charge are just enough for everything I need to accomplish in Davis.
Basics of eco-driving
I avoid charging at peak energy use times like summer days from 2:00-7:00 p.m. According to my wattmeter it takes 1380 watts while charging my car! I set a timer to remember to unplug the car and cable after 3 hours to avoid wasting unnecessary “phantom” electricity of 1.2 watts. I even consult a map to avoid wasting my charge hunting for an address. I deliberately avoid car congestion times and places, though on the EV mode, idling does not consume gasoline!
I keep the car supplied with shopping bags, but not much else as I don’t want any excess weight to drag on fuel consumption. Every extra 100 pounds reduces gas mileage by 4%!
I’ve learned just how to get the most from my Prius. I watch the gauges to be sure I’m on EV mode, and I drive moderately, with a light, consistent touch on the accelerator. Aggressive starts and stops gobble up the electric charge.
Gentle braking is actually advantageous as it recharges the regenerative braking to harvest more energy, thus extending the EV mode operation time. One time I made it all the way across the Yolo causeway on just .2 mile of charge because of the stop-and-go traffic. The heavy traffic forced me to break continuously which kept the car recharged!
That brings me to my out-of-town driving tricks. I drive to Carmichael once or twice a week to visit my 90-year-old father at a retirement community about 30 miles away, with no easy transit options. So, I drive the car gently and smoothly using up my EV miles just as I reach Ikea’s and sometimes even making it to the Sacramento River crossing. During that first part of my trip, I leave the radio and air conditioner or seat warmer off to maximize the distance on electric charge. The quiet time is refreshing.
Once I switch to the gas engine, I turn on the desired accessories but continue the slow, smooth accelerations, saving possibly up to 2 mpg. It happens that the whole stretch of I-80 I drive is posted at 55 mph, the exact point that is the most efficient driving speed, so I don’t exceed it. Every 5 mph over that adds $0.10 per gallon for gas.
Once at my father’s place, I pull into the garage and plug in. I pride myself on running my father’s errands on electric as well as heading back to Davis with a full electric charge. When we’re out and about on hot days, I always use my inside windshield sun-blockers to keep the parked car cooler and reduce our need for air conditioning that drains our electricity. On the freeways at speeds over 40 mph, the drag caused by open windows eats more gas than working the air conditioner, especially since I run it on recirculation.
My first longer car trip is coming up this June as we drive up to Portland, Oregon. We’ll be looking for places to charge up along the way to improve our gas mileage, but many times we’ll be just keep driving on the gas engine. I expect the trip may reduce our monthly percentage of EV driving, though.
I have a confession to make. I’m pretty good about the big maintenance items that call for servicing: changing the oil, tune-ups. I get it. But I also know it matters to keep the tires properly inflated just as I can tell when my bicycle gets harder and harder to pump because I don’t have enough air in the tires. I‘ve read that proper PSI levels can improve my gas mileage by 3.3%….but somehow I haven’t yet established the habit of checking regularly. I mean to. I promise myself I will. I make resolutions and notes. But the reality is, I don’t. So there’s my working edge!
Eco-driving + Prius Plug-in is a winner!
The results are in… and I have met the challenges I set for myself. Yes, I can manage all my Davis driving on the plug-in electric charge so long as I plan carefully! I must keep the car charged, group errands together, and use my bike whenever possible, too. Guilt-free driving is an enormous relief.
The gas mileage data I’ve collected is exciting, too. I’m not fossil-fuel free, but I’ve driven 19,865 miles, and I’m generally running 25% electric, so 4,975 miles on 1418 Kwh of energy. That translates into 118.4 gallons of fuel saved in two and a half years. The trade-off is roughly $4-$6 dollars of electricity per month which has its own carbon footprint. I’m rooting for a local Community Choice Energy program for Davis in the near future so my electricity sourcing will be green and local since my passive solar home roof cannot accommodate solar pv.
Most months, I drive the gas motor 75% of the time. I’ve now driven a total of 14,890 miles, using a total of 253 gallons of fossil fuel. This month I achieved 83.87 miles per gallon, but my average for 2014 was 74.6 mpg, and so far for 2015 it’s 69.5 mpg. That’s pretty exciting compared to my trusty 1996 Toyota Corolla which was a much smaller car and considered quite efficient with its stick shift and 5th gear, but it only gave me 30+ miles per gallon.
The combination of eco-driving and the Prius Plug-in is a winner!
*The EPA estimates 95 mpge in full electric mode and 50 mpg combined when using the engine. With a 25-75 split that would equate to about 61.25 mpg overall.
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