Chevy Volt Electrical Cost Analysis

I’ve been tracking the electrical usage of our Chevy Volt, Sparky, for the past couple of weeks.   Before we bought Sparky we did some research on the Volt’s electrical consumption and did some off-the-cuff cost projections.  Unfortunately, there was very little real world data available online, mostly because other bloggers weren’t able to monitor their Volt’s actual kWh utilization and were instead using the change in usage pre- and post-Volt.

That was my impetus for installing a kWh meter inline with my Level 2 charger,  a project that you can read about here.

I’m going to periodically update this post with fresh data as it becomes available, and the numbers below cover the period 6/13/2011 through 6/27/2011.

The electric rate used is based upon my last bill (our rates don’t fluctuate much anyhow), it takes into account all per-kWh taxes and fees, and we do not pay different rates based upon time of day.  Electrical service is provided by the Long Island Power Authority.

Those figures come from a spreadsheet that you can download here (Microsoft Excel 2007 format).  Please feel free to plug in your own electric rate if you want to get an idea of a Volt’s charging cost in your area.

Because the Volt’s computer tracks EV Miles (miles traveled on battery), the calculations are fairly simple:  I subtract the first EV Miles reading taken from the last EV Miles reading, and subtract the first kWh reading from the last.  Dividing those two figures yields the Miles / kWh, and the rest is pretty self-explanatory.

One minor caveat:  Some battery (the “buffer zone“) can be consumed while running on gas.  Recharging that portion of the battery is reflected in my kWh numbers, but is not reflected in the EV Miles.  That’s not necessarily a bad thing because it will make the cost per EV mile slightly higher than it should be, and we’re still saving quite a bit of money on a per-EV Mile basis regardless.

Over her lifetime, Sparky has traveled 82% of her miles in electric mode, and 18% in gas mode.

As you can see, the bottom line is that it costs about $1.85 to travel 35 miles in Sparky.  In my area gas prices are about $4.13/gal. (as of last time I filled up my Jeep), and that is what it would cost to travel the same distance in a car that gets a real-world 35 MPG.

My Jeep Wrangler gets around 13 MPG, and so it costs me a whopping $11.12 to travel 35 miles.  (Geez, this is the first time I’ve actually done that calculation and it’s kinda scary).  You can see why my wife and I take Sparky whenever we go anywhere together — it saves us about $9.27 on a 35 mile trip!

To go even further, let’s look at the cost/mile of a few cars*:

Jeep Wrangler Rubicon Unlimited (13 MPG):  $0.30

Saab 9-3 SE Convertible (27 MPG): $0.15

Toyota Prius 11 (51 MPG): $0.08

Chevrolet Volt (Electric only):  $0.05

Nissan Leaf:  $0.05

*The figures for the Saab, Jeep, and Volt are based upon my own readings with my and/or my wife’s driving habits.  The figure for the Prius is based upon a non-PHEV-converted vehicle, using Toyota’s highest MPG figure.   The Leaf’s cost is estimated based upon the 3.4 miles/kWh supplied by the EPA.  And I’ll even use a lower gas cost of $4/gal. to prevent octane-related arguments.

In case you’re wondering why I’m using 35 miles for most of my comparisons:  The Volt gets about 35 miles per charge (usually more), on gas 35 MPG is between our real-world usage and the window sticker rating, and it seems to be that other comparably-equipped 4-door cars land near the 35 MPG mark (according to their window stickers, anyhow).

I’m looking for feedback on my calculations or reasoning, so please email me or let me know what you think in the comments.   The numbers should be more accurate as I accumulate more sample time.