Thursday, October 23, 2014

Only 3 cents a mile

How much does it cost to drive a gasoline powered car a distance of one mile?  The price varies by a number of different factors, including the price of gasoline, the cost of an oil change, the cost of an emissions test, and the cost of a minor tune-up.  The fuel efficiency of the engine also figures in significantly.  A typical small sedan might average about 25 miles per gallon.  Gasoline fluctuates between $3.50 a gallon in the winter and $4.50 a gallon in the summer, so I’ll pick an average price of $4.00 a gallon.  I can get a smog check every two years for $60, an oil change every 5,000 miles for $80, and a minor tune-up every 15,000 miles for $150.  (There are other service items too, but these will make my point.)  The cost to drive this small sedan 30,000 miles over three years is:

smog check
oil change
minor tune-up

That amounts to $0.19 a mile.  (A SUV that gets 16 MPG costs $0.28 a mile.)

The cost to drive an electric car is basically a function of the cost of electricity and the range per kilowatt-hour.  Assuming electricity can be bought for $0.145 per kWh, and a typical range of 4 miles per kWh (according to the EPA), then the cost per mile is (simply) $0.036.  My car is fast approaching 30,000 miles on the odometer, which means that I have saved approximately $4,600 over the cost of driving a small gasoline powered sedan.  Of course, I squandered my savings on additional solar panels, which dropped my electric bill to about $85 a year to drive 10,000 miles, saving me another $825 over the same three years.  (And, the solar panels should remain in service for 20+ years.)  So, when figuring the total cost of a gasoline powered car, you need to think beyond the sticker price and look at the additional costs of ownership.  Even factoring in a new battery after 10 years of driving I still come out thousands of dollars ahead.

Saturday, October 11, 2014

The carpool lane

One of the big incentives for most electric vehicle customers in the San Francisco Bay Area is the access to the diamond/carpool lane.  For commuters that have inflexible work hours, driving in the carpool lane can cut ten minutes or more from your trip.  Because of the hours I tend to drive, the carpool lane is seldom an option for me.  Along my route to work, the carpool lane is restricted only during the morning and afternoon peak hours, and I tend to commute just after each of these restricted periods.  So, most of the time, the carpool lane is not a viable option.  Of course, the carpool lane is not without its costs either.

Like any car, an electric car uses the least amount of energy when a steady speed is maintained.  Although stops can recapture up to one-third of the energy used to accelerate, it cannot recapture all of the energy, nor do you recapture the steady-state energy.  The trouble with driving the carpool lanes is the unpredictability of the flow of traffic.  At any moment, a car ahead of you may need to slow in order to change lanes, or another slower car can pull in front of you from an adjacent lane.  Finally, getting into the carpool lane often requires harder acceleration than simply pulling onto the freeway (if you want to avoid a rear collision).  So, on those few trips I take when the carpool lane is available, I tend to evaluate the flow of traffic outside the carpool land and decide whether traffic is moving steadily or stopping and starting.  I will stay in a steadily moving lane as long as the speed is at least 30 MPH and elect to use the carpool lane when it drops below that point.  (Besides, driving at these slower speeds uses substantially less energy.)

So, if I seldom use the carpool lane, even when it is available to me, why did I bother applying for the special decals allowing me to do so?  The other diamond lane available to me is found at metered freeway onramps, where a traffic signal controls which cars enter the freeway and how often.  At some of these metered entrances, a diamond lane has been set up affording carpoolers a shorter wait to get into traffic.  These express ramps can save as much as three to six minutes time getting into traffic on the freeway, and I take advantage of them every chance I get.

Saturday, October 4, 2014

How far is 60 miles?

Before buying my Mitsubishi i-MiEV, I read the expected range and then started paying attention to my daily driving habits.  The predicted range for the car is about 62 miles when fully charged (according to the EPA).  That seems quite short, considering that I would refill my gas tank every other week.  My drive to work wasn’t much of a concern because my travel round-trip was about 19 miles, and the planned relocation would double that to nearly 40 miles, both within my car’s range.  My bigger concern was how far I would drive on weekends.  I knew that certain weekend excursions would be beyond the reach of my car, so I ignored those trips.  Instead, I started paying attention to the trip odometer on my gasoline-powered car on weekends.  As it turned out, while I did a lot of driving running errands and such, I seldom drove more than 35 miles in a day, and often less.  So, it seemed that the car can meet the vast majority of my driving needs.

Once I got the car, the next challenge would be to see how far it can drive comfortably without needing a recharge (or only a small one).  My first extended trip was to a wine store about 26 miles to the north, which the car completed comfortably with some miles to spare.  Another time I had to drive to work and back and then to a relative’s place about 6 miles east from home.  After getting to their house, I learned I had to make another trip to another house about 15 miles to the south, and then drive home another 11 miles.  All this was in addition to my usual 40 mile commute.  I drove the freeway on the 15 mile leg, and streets on the 6 mile stretch.  Looking at the charge level, I decided it would be best to take streets home along the last 11 miles.  The 72-mile day left me with 5 miles of range indicated, with the last bar on the charge gauge flashing.  This was my longest drive without recharging.
My challenging trip to Oakland left me very charge nervous.

My third adventure was a little more nerve-wracking.  I needed to pick up a package (yes, more wine) about 37 miles from home to the north in Oakland.  The trip was entirely freeway speed, so I needed to be very careful of the distances.  I knew I could not make the full trip on a single charge, so I found a Target store on the way home that offered charging.  The distance to Oakland and back to Target was just about 60 miles, so I figured I could stop there for two hours, recharge, shop, and get back on the road.  The freeway drive drained more of the battery than I had hoped, so by the time I was looking for the exit to get to Target, the last charge bar was again flashing.  Luckily I had studied the map well and did not miss any turns.  I got to the charger station with 4 miles of range remaining.  But when I tried to start charging, my ChargePoint card was rejected because I hadn’t set up the credit card option.  A panicked phone call resolved that problem but left me with only 80 minutes in my schedule to charge.  By the time I arrived at home, the last bar was again flashing.  Even though I made it safely, I have decided to take my gas car from now on to this place (about twice a year).