Plugged-in readers have much to say about hybrid costs

TO PLUG OR NOT TO PLUG: Fluxuating gas and electric prices can change the calculus on the true cost of being green. Bill Griffith

By Bill Griffith

May 10, 2015

4 minutes to read

Thanks to all the readers who’ve emailed over the past decade or more. Almost all your emails are interesting, informed, or ask a legitimate question. Here’s a sample of what you had to say about the Prius Plug-In.

Letter 1

Thank you for writing about the Plug-In Prius (PiP). I own a 2012 PiP and figured out that the 95 MPGe [government’s combined gas/electric mpg rating] is elusive. I’m fortunate to have a garage, but at the current gas prices I won’t plug in. Here’s why:

The battery capacity is 4.4 kWh (kilowatt hours); however, I understand that only 3.4 kWh is actually usable to prolong the life of the battery. I will run the numbers using both 4.4 kWh and 3.4 kWh just in case someone is a skeptic.

The 4.4 kWh battery will get you 15 miles of all-electric driving, which is about 3.41 miles per kWh. That means to get 50 miles (the miles from one gallon of gas) from the electric battery, I would need 14.67 kWh in total (50 miles/3.41 miles per kWh). Here in the Boston area (after the recent electric price increase), I pay $.235 per kWh. The cost of the 14.67 kWh for me is $3.45 ($.235 per kWh x 14.67 kWh). So, when gas is above $3.45, it pays to plug in.

Now, assuming there are only 3.4 usable kWh in the battery:

The 3.4 kWh will get you 15 miles, which is about 4.41 miles per kWh. That means to get 50 miles from the electric battery, I would need 11.33 kWh in total. Using the $.235 per kWh, the cost of the 11.33 kWh is $2.66. So, when gas is above $2.66 it pays to plug in.

Where I live, the cost of a gallon of gas is less than $2.50, so I don’t plug in.

I think the 95 MPGe (the Prius Plug-In’s EPA rating) was calculated when or where electric rates were significantly less than they are here and now, or for a vehicle with a better kWh utilization ( all-electric cars can get many more miles out of a kWh).

Steve D. (a happy PiP owner)

Steve: Thanks for the math-made-almost easy explanation.

Letter 2

I have had three generations of the Prius, the last a 2012 plug-in.

I traded that for a 2014 Volt.

No comparison between the two. The Volt gets 38 electric miles (58 in the summer). It’s perfect for short trips, especially if you are retired and live in a small town. It has an 8-plus gallon gas tank.

All in all, the Volt is a perfect car for me.

And you can safely use the heater. I remember getting very cold trying to squeeze in a few extra electric miles with the Prius.

Norton H

Norton: I’ve always thought the Volt would have had the sales position that the Prii family now occupies if only GM had stopped talking about the “coming Volt’’ and actually got it to market two years earlier.

Letter 3

I got one of these (Prius Plug-In) in November, 2013. Gas was $3.40/gallon and electricity $0.17/kWh when it made sense to plug it in. Now gas is $2.40/gallon and electricity is $0.24/kWh. Do the math. It is now cheaper to run on gas alone. A second benefit of all hybrids is an inverter that can be used in place of a generator during power outages.

Peter S

Peter: Now we need an electrician-physicist-handyman to explain how that reverse inverter hook-up works.

Letter 4

How about analyzing cost benefits over time? Is it worth shelling out $35,000 up front to get the 50 mpg?

Also, your difficulty in getting plugged in at a condo complex could be a BIG problem for some owners, depending on how accessible an outlet is.

How about battery life and replacement cost?

Personally, I’m very happy with my redesigned 2014 Corolla: decent mpg, plenty of interior space, a history of good reliability.

Lou S

Lou: First things first. The Corolla is a great choice. Second, I’m not the math whiz that Steve (1st letter) is, but assuming you drive 15,000 miles a year and average 25 mpg overall, you’ll use 600 gallons of gas. At $3 a gallon (for round numbers), you’ll spend $1,800 a year. If you average 50 mpg, you cut consumption (and cost) in half, to $900 a year. Depending on how much of a premium you pay for a hybrid and gas prices, the payback or break even can take four to eight years. One other hybrid advantage: Maintenance costs generally are significantly lower.

Letter 5

I just read your column about the Prius Plug-In and hope you may be able to help me. I want to buy a plug-in hybrid (mostly for the tax advantages) and have looked at the Volt and the Ford C-Max as well, but I cannot find a dealer who has a Prius Plug-In on the lot.

My dealer (I own a 2007 Prius) says I have to order one sight unseen, but I’d like to test drive one first because I have read about the noisy engine and the cheap interior.

Do you know any dealer in Massachusetts who has a plug-in on the lot? It feels as if the dealers don’t really want to market the plug-ins.

Judith B

Interesting, Judith. An April 30 search of CarGurus.com showed no Prius Plug-Ins at any Massachusetts dealers, though there were some in Rhode Island, Maine, and New York.