Prius Plug-in Versus Volt: Which Costs Less to Drive?

By · October 17, 2011

Now that Toyota’s Prius Plug-in Hybrid has been officially announced, we can begin the comparisons with the other plug-in electric vehicle with an extended driving range, the Chevrolet Volt.  The underlying question is which is more important to consumers: electric driving range, or total vehicle fuel efficiency?

The folks at Edmunds.com’s AutoObserver pointed out that the Prius PHEV will earn the right to drive in the HOV lane in California (because of the low total emissions), while Volt owners won’t have that luxury.  Conversely, Volt buyers get the full federal tax credit ($7,500) because of the larger battery pack, but Prius PHEV owners get the smaller amount ($2,500).  Still, the Prius overall will cost about $2,000 less after you figure in the tax credits. 

Winning the hearts and wallets of consumers could come down to one number – but will it be 35 (as in the Volt’s estimated miles of electric range, per the EPA), or will it be 49 (as in the total MPG that the Prius will achieve in hybrid mode)?

At 37 MPG after the batteries are depleted, the Volt ain’t no Hummer or Escalade.  And with 14 miles of electric range, the Prius PHEV offers much greater silent driving than the original Prius. 

But which vehicle will cost more to drive based on how far you go between charges?

Assuming a gas price of $3.50 and electricity at 11 cents per kilowatt-hour, the Volt’s bigger battery makes it cheaper to operate as long as you drive 70 miles or less between charges.  At distances of greater than 70 miles, the Prius PHEVs’ greater fuel economy as a hybrid makes it cheaper to operate. 

Cost of Driving a Plug In Vehicle Based on Trip Distance

This is one scenario, and the conclusions may change if the price of gasoline goes up or down, or depending on the cost of electricity in your neighborhood.  Also, the calculations for both vehicles assume that the gas engine is not engaged until the full electric driving range is completed, which may not be true depending on driving conditions and driver behaviors. 

However, the graph illustrates that for most trips (<70 miles in between charging), primarily driving on electric power makes the Volt cheaper to operate. 

Comments

· · 3 years ago

John,
Thanks for doing these numbers. I have a few colleagues with insane commutes that are looking for alternatives. Since neither the Leaf nor the Volt can go without gasoline, I've assumed the PIP probably is the better alternative. I've always known that the PIP's carpool lane access would definitely swing them but I also suspected (and you've computed) that the PIP would actually be the cheapest for them as well. In CA, where gas prices are around $4/gal, I suspect the numbers will be similar.

· JeffN (not verified) · 3 years ago

The Prius Plug-in is not actually available for sale so comparing it to a currently available Volt on the basis of carpool lane access is irrelevant. Within 3-4 months after the Prius Plug-in becomes available in the Spring of 2012 in selected states the Volt will be available for order in California and other states that meets the same Enhanced AT-PZEV requirements, according to GM.

The supposed 14-15 mile all-electric range of the Prius Plug-in also cannot be compared to the EPA
estimated 35 mile electric range of the Volt. Toyota's electric range claims are based on the European test cycle (14.3 miles) or perhaps similarly easy EPA sub-tests like the UDDS (their 15 mile U.S. PR claim?) which is almost never quoted by itself. The Volt (Opel Ampera) scores 52-53 miles of battery range against the same European test cycle under which the Prius Plug-in gets an unofficial 14.3 so the assumptions underlying your graph are probably wrong.

· · 3 years ago

Great review. Pretty cool and it helped us out here.

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· · 3 years ago

A compact car (Volt) should cost less to operate than a midsize (Plugin Prius).

Volt requires premium gas while Plugin Prius runs on regular. The difference about 40cents per gallon was not accounted for.

· · 3 years ago

John, I really liked this comparison and the graph to show the results. What surprised me is how close the lines are to each other. For most people the difference in price per day is less than a dollar.

Right now I currently own an 06 Prius and I am on the waiting list for a Leaf. I have always thought that my 2 car garage would some day have one fully electric car and one Plug in hybrid ( Volt or Prius).

The price of the 2 plug in hybrids is so close together it might be best to rent each of them for a week and then see which one is your favorite after that.

KJD
http://www.evalbum.com/3175

· Charles (not verified) · 3 years ago

Why is there an inflection point at 30 miles for the Prius?

· theflew (not verified) · 3 years ago

Another difference besides just the small difference in operating cost is how much more enjoyable it is to drive a Volt.

· David K. (not verified) · 3 years ago

I drive a Prius PHEV conversion now and have to say it's hard to justify replacing it with a Volt, a tank of gas lasts more than a month in city driving and it still gets 45-50mpg on the road. It's a great, practical car with lots of room and has been very reliable. That said it's pretty much a "tranportation appliance" and is not particularly fun to drive like the Volt is. I have a Leaf on order and plan to keep the Prius as a second car, but if I had lots of money I would probably replace it with that new Caddy Volt (is it the ELR?) when it comes out.

· · 3 years ago

@Charles, I was going to ask the same question. I understand the inflection point for the Volt at around 30 miles because that is when you start using gas. By that logic, the inflection point on the Prius should be at or below 15 miles. Also, JeffN is correct in that these pure EV ranges are not based on the same drive cycle which may put the Prius inflection point at a much lower point, maybe as low as 8-10 miles. Another issue I have with the graph is that the lower slope line (electric only part of the trip) on the Volt doesn't pass through 0,0 yet the Prius does. Also, the Volt is physically capable of keeping the engine off for ALL speeds below highway speeds (I believe you have to get above 70 mph before the engine is needed to be charge neutral). The current production Prius can not physically keep the engine off under all driving based on the transmission (planetary gear) configuration. It can only achieve 62 mph under "light" accelerator pedal and will start the engine during accelerations below this speed (the Volt is robust to this). Also, most trips are less than electric range of the Volt but more than the electric range of the Prius. All of these fact will push the Prius cost of driving much higher than the Volt for real life driving.

· George Parrott (not verified) · 3 years ago

We migrated from a 2006 Prius and 2007 Camry Hybrid to the 2011 Volt AND Leaf. I agree totally with "regman" as to his observation that the PIP will always kick in the ICE when accelerating strongly even in the first mile of what "could" be EV range. Further at true freeway speeds, the ICE will engage even if there is still battery capacity. To my way of thinking, and even as a long-time Toyota customer, the PIP is a poorly engineered evolution of the regular Prius. The EV range and power are way too limited to truly achieve "emission free" driving at least in our daily commuting.

The Volt is a more rewarding package to drive than either of our earlier Prius models (we also had a 2004 Prius) and it handles and rides more like our earlier Audi (firm and flat in the corners) than our more recent Camry Hybrid. The electronics to manage the EV process and the overall "feel" of the Volt is so much more polished and well-integrated than the Leaf that after even the first month of driving both, it was absolutely clear that the Volt was $8000 MORE car than our fully optioned Leaf. We are totally committed to reducing our vehicular emissions, and the combination of a pure EV and a significant range extended range EV meets our daily needs and personal values. The PIP was a total "non-starter" for us.

· JeffN (not verified) · 3 years ago

@regman
"Also, the Volt is physically capable of keeping the engine off for ALL speeds below highway speeds (I believe you have to get above 70 mph before the engine is needed to be charge neutral)."

The Volt is a full-power EV, unlike the blended power design of the Prius Plug-in. The gas engine in the Volt remains off while the usable capacity of the battery still has charge remaining. This is true even for speeds above 70, extreme acceleration or steep road grades.

After the usable capacity of the battery charge has been used (typically 35-50), the Volt switches into a hybrid mode where it operates somewhat like a Prius except with a larger electric motor and a larger hybrid battery power output capability.

· · 3 years ago

@JeffN
You are correct. I went back and re-read Nick's Volt article from a year ago as well as a wireddotcom article that corrected some of the original explanations of the use of the engine. According to my new understanding, above approximately 70 mph (not a hard point), the engine will come on to provide drive assist only during charge sustain mode (after the 30 miles EV driving) and may or may not provide direct, mechanical power to the wheels depending on if the system thinks it is more efficient to control that way. My point still stands though; the Volt has a much larger window of operation than the PIP.

· hxp417 (not verified) · 3 years ago

To count the "total cost of ownership", the best solution might be a regular Prius + a Leaf.

For some families, count in their lifestyle and practical usages, the optimal solution could be a van or light SUV (either regular ICE or hybrid) + a pure electric car (such as Leaf). coz usually one of the couple commutes short distance (or stays home), another one drive longer distance to work.

· · 3 years ago

@JeffN: Yes, PiP is a blended plugin hybrid. If you want maximum power, it'll use both powertrains, as it should.

If gas is used to blend, the electricity consumption drops to half of what Volt consumes. That's the beauty of a blended plugin. Gas is used to cover the peak power demands and that also extends the EV range.

· Emc2 (not verified) · 3 years ago

Very nice comparison but there seems to be a mistake in the graph because it shouldn't be an inflection point for the Prius at 30 miles. After the battery is depleted the curve should have a constant rate equal to the Prius mpg.

· · 3 years ago

Great comparison...... I would add that my 2012 Volt regularly hits 40 miles before switching to the ICE.

· Mike I. (not verified) · 3 years ago

The chart is definitely strange. The chart should start from zero and assuming that the pure electric efficiency of the two cars is equivalent and neither car uses any gas at the start of a trip, the two lines should overlap until the trip distance reaches 15 miles. Since the Volt is petro-free until the battery reaches a certain level, the inflection point in the blue line at 30 miles implies that John is estimating that the ICE will kick in at that point. The slope of the line from there is proportional to the price of gas and the MPG. The inflection point in the red line at 30 miles implies that the Prius PHEV has some significant blending mode where the efficiency is significantly higher than a standard Prius between 15 and 30 miles. I would be interested to see the analysis that supports that. The most simplistic analysis, based purely on EPA figures would have one inflection point for each vehicle. The Prius PHEV should be at about 15 miles and the Volt at about 30. I would like to see this chart based on real OBD data logging.

· Art (not verified) · 3 years ago

The problem with the graph is quite simple. The 15 mile point on the x-axis is in the wrong place; it should be moved over one tick to the right and the 0 origin placed where the 15 is. Then the PIP inflection point goes away and the two plots will overlay from 0 to 15.

· Anonymous (not verified) · 3 years ago

There is something wrong with that graph. The cost diagram should have only one inflection point for each vehicle and two gradients, one in electric mode and one in ICE mode.

Based on the article's numbers, the Prius should have its inflection point at 14 miles, and the Volt at 35, but in this diagram, the Prius shows two, one correctly placed at 14 (although not clear because the graph does not show that both lines extrapolate to (0,0) from that intersection point) and another at 35, which is not true as the Prius does not suffer a behavior change at that point, it is already and ICE and continues being an ICE. I did the calculation myself assuming from the graph that they use 0.3 kWh per mile in EV mode and found the intersecting point at 70, which means the conclusion is correct, but the mathematical representation lacks skills.

· Charles (not verified) · 3 years ago

Anonymous, I second your conclusion. I changed the cost of fuel to 3.75 for the Volt and assumed $0.02 cost per mile while in EV mode for both cars. With the Prius having a 14 mile EV range and the Volt 35 miles. The cross point is at 72 miles. So again the graph is wrong, but the conclusion is correct. None of us are exactly correct. I would assume that the Prius is cheaper than the Volt while both are in EV mode, because the Prius is a more efficient car. The problem for the Prius is that it seems impossible to drive it in a normal manor and keep it in a pure EV mode.

· JeffN (not verified) · 3 years ago

@Mike I.
"The Prius PHEV should be at about 15 miles and the Volt at about 30."

This chart needs to be based on consistent test cycle results. We don't have published EPA estimates or even self-reported preliminary EPA numbers for the Prius so that rules out using the 35 mile EPA combined city/highway electric range estimate of the Volt. However, we do have a preliminary European test cycle electric range estimate that Toyota self-reported during the introduction of the production 2012 Prius PHEV at the recent Franfurt 2011 auto show. Toyota reported an estimate of 23 km or 14.3 miles. The production 2012 Opel Ampera (Chevrolet Volt) has a published European test cycle electric range of 83 km or 52 miles.

A consistent chart would use 14 miles for the Prius and 52 miles for the Volt.

· JeffN (not verified) · 3 years ago

The European test cycle (NEDC) electric range results for the Nissan Leaf are 175 km or 109 miles whereas the EPA range estimate is 73. So here is a handy comparison table:

Prius PiP Volt Leaf
-----------------------------
NEDC 14 52 109
EPA 10? 35 73

If you really want to use 35 miles as the Volt's electric range then a reasonable guess for an equivalent Prius Plug-in all-electric range would be 10 miles.

· Charles (not verified) · 3 years ago

So the bottom line is that the Volt is cheaper to drive if your between charge drives are under somewhere between 70 and 75 miles. If your drives are under 10 miles both cars are about the same. Over 70-75 and the Plug In Prius is your cheapest option.

So for me the Volt would be the cheaper option. My drives range from 10-70 miles a day. I have only a few trips a year go past 75. When the do go past it is closer to 500 miles, where the Volt would cost me about $12 more.

· kballs (not verified) · 3 years ago

I speculate that the pip won't even have an all-electric range under the epa test cycle because the gas engine will kick on under one of the first acceleration cycles. Toyota needs to put a bigger electric motor in that thing. That makes Pike's graph even more bogus than it appears at first glance, the break even point is probably over 100 miles in practice, but in the real world almost nobody drives that far on a daily basis.

· JeffN (not verified) · 3 years ago

@kballs
"I speculate that the pip won't even have an all-electric range under the epa test cycle because the gas engine will kick on under one of the first acceleration cycles. Toyota needs to put a bigger electric motor in that thing."

I agree that your speculation is very likely to be true. The 'weak' link in Toyota's design is actually the small battery which has a maximum power output of 27 kW (same as non plug-in Prius). Even the city-oriented UDDS EPA sub-cycle has one point early in the test that likely draws more than that. The highway aspects of the EPA test formula are all but certain to require more than 27 kW at various times.

For PR purposes, Toyota could ignore the gas consumption and just count the electric assist or they could trim out the parts of the test cycle that require the gas engine and just run the parts of the test that the battery can keep up with. However, if you do that you end up with artificially inflated results because you end up removing the hard acceleration parts of the test that would have generated the worst efficiency results. I suspect the EPA will not include an all-electric range estimate in the official results because the PiP uses a blended design.

The PiP is fundamentally a different design variation than the Volt. It should do a great job at reducing gasoline consumption versus the regular Prius when driven short distances on a charged battery. For people with very short commutes or the ability to charge during the day it may be good option.

For many drivers a Volt will reduce their gasoline consumption further and with only once-daily charging. The Volt will also have the better driving experience of a full-power EV even, to a large degree, after it runs down the battery and switches to hybrid mode because the larger battery can inherently put out higher kW when needed.

It's good to have choices like this! One car design can not fit all needs.

· · 3 years ago

@Charles "Why is there an inflection point at 30 miles for the Prius?"

Yes - there is a problem with the graph. Inflexion point for Prius PHV should be differen and occur around 15 miles - not around 30. I think it is a typo in the data used for the graph.

The cross over would also happen a little later once this correction is done.

· · 3 years ago

@usbseawolf2000
"Volt requires premium gas while Plugin Prius runs on regular. The difference about 40cents per gallon was not accounted for."

I don't know where you are getting your gas, but at Chevron and Shell, I have never seen anything but $.20 per gallon difference, whether the gas was $2.00 per gallon or $5.00 gallon.

· · 3 years ago

"The folks at Edmunds.com’s AutoObserver pointed out that the Prius PHEV will earn the right to drive in the HOV lane in California (because of the low total emissions), while Volt owners won’t have that luxury."

This may not matter for much longer. The state and transit districts want to replace taxpayer paid for HOV lanes with toll lanes. All the clean vehicles, including electrics, are getting kicked out of the replacement toll lanes. Lanes are being built soon for the 10 and 60 freeways.

This is yet another brilliant move by the state wrecking California legislature and leaders, where lining their pockets with tax money takes priority over everything else, including common sense.

· jim1961 (not verified) · 3 years ago

Both of these vehicles are incredibly good, state-of-the-art PHEVs. The big winners in this contest are the consumer and the environment. It will be interesting to see how the Ford C-Max Energi PHEV compares to Volt and PIP when it's EPA numbers are released.

· Anonymous (not verified) · 3 years ago

I believe that it's incorrect to state that Volt is cheaper to drive or own than the PIP if charge period is less than 70 mi. Remember, the graphs only indicate fuel cost vs distance, not ownership cost over distance.

As shown on the graph , the difference is at most 60 cents or so when < 70 mi. Assume that one can get all the tax rebates for either vehicle, price difference is $2000. That means ~ 3300 charges for the PIP to actually cost the same as the Volt. If 1 charge per day (for either vehicle, no 2 charges/day for PIP), that's close to 10 years before PIP actually cost the same as the Volt, if price of fuel remains at the current level. Since most people don't hang on to their vehicles after 5-7 years or so, esp when either of these vehicle's batteries will become non-usable at that point, it's unlikely for Volt's owner to come out ahead, $ wise, against PIP.

Thus, PIP is a winner in terms of real cost of operation.

· · 3 years ago

The inflection point at 30 miles is due to the x-axis interval change from 15 to 30.

I created a new graph with 5 miles interval. I also considered the price difference between regular and premium gas.

Even if I use a conservative 10 miles EV range for Prius Plugin, the two lines interests at 55 miles mark at $3.48.

See the graphs and spreadsheet with calculations at:
http://priuschat.com/forums/toyota-prius-phv-plug-in/99125-prius-plug-in...

· Giuseppe (not verified) · 3 years ago

I don't think the methodology in the article is worthwhile, so I propose a different one. My methodology is based very roughly on the Department of Transportation estimated distribution for all car trips made by American drivers. The battery is recharged after every trip. So I assume that the Prius, with an electric range of 15 miles, can drive 50% of its miles on electricity, while the Volt, with an electric range of 35 miles, can drive 75% of its miles on electricity. Also, the Prius gets 49 mpg and 4 miles/kWh, while the Volt gets 37 mpg and 3 miles/kWh. Finally, assuming the cost of gasoline is $4/gallon (and allowing the Volt to use regular gasoline even though GM says the Volt should have premium) and the cost of electricity is 15¢ per kWh (the national average is presently lower for both gasoline and electricity), every 1000 miles driven costs $59.57 in the Prius and $64.53 in the Volt. Therefore, the difference is $4.96 per 1000 miles. This is a rough number, but it should be about right for the average American driver. If you prefer the author's costs for electricity and gasoline, the difference will change a little. Also, if your driving habits bias you towards shorter trips between charges, the Prius will be more advantageous, while a bias towards longer trips will favor the Volt. However, the most important result seems to be that as long as the price of oil does not increase significantly (it's about double this in Europe) the cost difference is very small.

· · 3 years ago

@Giuseppe,
Don't forget that the PIP only works in EV mode at speeds below 62 mph (100 kph) so that adds another bias to its usefulness relative to the Volt.
Also, while you mention the assumption that oil prices don't increase, many of us have seen gas prices rise from $0.25 per gallon to $5.00 per gallon and realize that India and China are only beginning to become heavy gasoline consumers. We don't see that assumption as being very realistic.
The PIP will meet the oil-free transportation needs of a lot fewer people than the Volt so when gas prices spike, the Volt is going to go a lot further towards saving us than the PIP.
Its good to have the choice but I'll yawn through the PIP and throw my support towards companies who really want to make a significant difference, not just try to squeeze a bit more easy money from their current cash cow.

· Giuseppe (not verified) · 3 years ago

ex-EV1 driver:

The 62 mph electricity limit for the Prius PHEV will not significantly change the amount of electricity used annually. I agree that gasoline prices are likely to rise as China and India raise the demand for oil. My phrasing was intended only to show a limit on the validity of my own calculation. However, gasoline prices are not likely to spike, but rather to rise fairly smoothly over several years, during which time both Toyota and GM will have the opportunity to tweak their PHEV designs. And at the same time, battery prices are likely to fall a little, or possibly a lot if some of the present research leads to a breakthrough or two. A change in the size of the battery would be very easy to accomplish.

As presently designed, clearly the Volt benefits relative to the Prius with higher gasoline prices or lower electricity prices. But remember that the initial cost of the Volt is higher by about $2000, so the overall cost of buying and operating the Volt only becomes lower after a few miles of driving. To get a feel for this, I redid my calculation using $10/gallon gasoline and 10¢/kWh electricity. In this case the fuel cost for the Volt is $21.97 lower per 1000 miles than for the Prius. In order to make up for the initial extra $2000, the owner would need to drive 91033 miles to break even.

· Sparkey (not verified) · 3 years ago

I am a VOLT owner. Currently I have 1233 miles on my VOLT and have used 1.9 gallons of gas. You will NEVER have this option from a PRIUS. You also fail to mention that once a sufficient infrastructure is built the VOLT will be the best value beyond the 80 range you mention.

· Anonymous (not verified) · 3 years ago

@ Sparkey,

Sorry to put ur ambition down, but u r incorrect when stating that a sufficient infrastructure will help Volt's value. When such is available - and I'm assuming QC stations that u r referring to, the Volt will have little to no value. Why? Because you are essentially in electric mode all the time, right? Then it's actually more beneficial to get a EV like the LEAF, Coda, iMeV, etc. which are cheaper in price (except Coda) and lower cost in maintenance.

In addition, PIP will also benefit from such since it can plug in more often as well, thus canceling any benefit that the Volt may seem to have. Seriously, we are dealing with 20 mi EV range here (approx) b/n Volt & PiP. Not that of a big deal. That 20 mi in gas $ vs electricity rate is 'bou $1.50 at today's $4/gal rate. Remember, you've to pay, with all tax deductions and whatnot rebates, $2K more to get the least expensive Volt.

Thus, for fuel cost, the Volt thus have a benefit.
For operation cost, including ownership cost, PIP wins the race.

This is pure finance/math. Has nothing to do with which one is better (technology or brand). If it's for me, I'll get a base Insight if I want to save money and help the environment. I do have a LEAF (lease), because with all the rebates and whatnot, I only pay $1K more than the base Insight (lease). I have saved a lot on fuel, however - $60 for 3000 miles so far, cheaper if I'm not too lazy to use the free chargepoint station 3 mi from where I live.

· Giuseppe (not verified) · 3 years ago

Sparkey:

Your 1.9 gallons of gasoline should be good for about 70 miles, so you have presumably driven nearly 95% of your 1233 miles on electricity. Would you care to share some details about your driving pattern, such as how far you commute, how often you recharge, how far you drive for various errands, and anything else you think is important? The Volt may be the perfect car for you, but I don't think you are the most typical American driver.

· Environut (not verified) · 3 years ago

I can't believe all the bickering and nickeling and diming going on on this page! In my opinion it's really cool that we FINALLY have options for getting somewhere without foreign oil. I'm on my second Prius and love it so much that even my skeptical husband has come around and drives it when I don't need it! I test drove a Volt and can't believe General Motors put a Chevy moniker on it. It drives like a Cadillac and is priced like a Cadillac. If Volts were in Caddy dealerships I think they'd be flying off the lots! General Morons... I was waiting for the plug-in Prius but now I might just have to buy American and get that sexy Volt.

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