Volt Energy consumption, MPG etc.. - Chevrolet Volt Forums: Chevy Volt Forum
 
LinkBack Thread Tools Display Modes
post #1 of 10 (permalink) Old 04-27-2013, 08:26 PM Thread Starter
Junior Member
 
Join Date: Apr 2013
Posts: 5
Volt Energy consumption, MPG etc..

I recently decided to make the step to an electric car and of course chose a Volt as in my mind it is the best alternative today. It is the only one that gives you a full electric vehicle but with the safety net of not being bound by the charging possibilities.
Given the technology is still young, that interest rates are low and that lease incentives on this car is high, I went for a 36 month lease.
Prior to making the jump, I ran a number of calculations to figure out my gas savings so I tough I would share this data for those who may be looking.

But let us be clear, as far as I am concerned, the cost saving is just a Bonus when you use a Volt. The satisfaction is much bigger than just that part 

If someone catches any errors in my reasoning, please feel free to chime in. I also have a link to an excel sheet at the end so you can play with the numbers

Base Parameters
Battery capacity: 16.5 kWh
But as pointed by TSquare, there is an SOC of 34.6% so
Actual usable battery: 10.8 kwh
My average miles per charge: 42 miles
As a result the number of miles I make on one kWh is:
Miles per charge / battery cap = 42 / 10.8 = 3.89 miles /kWh

Cost of gas:
Let us say you have a car that makes 26 miles per gallon like mine did:
Let us say you drive 12000 miles / year or 1000 mile /mth
Take a price per gallon of $4.5
Your gas consumption per month is:
Miles per month / Mile per gal = 1000 / 26 = 38.5 gal per month
Cost of gas per month is:
Gal per month x $ per gal = 38.5 x 4.5 = $173.1 of gas per month

Cost of Electricity:
Now evaluating the cost of electricity for the car depends on a lot of things and it can be a bit complex. To simplify it, you can assume you will be charging mostly during off peak hours and some during part peak (if this is the rate system you choose), or an EV rate if you use a separate meter for the car. You need to figure out the kWh price for these rates, and make sure it includes all the costs.
For me I decided to start without a 240 volts charger, so my charging time is 10 hours
Off peak is only 7 hours per day (midnight to 7AM), so at best I can charge 7 hours off peak, and 3 hours on part peak.
I figured out that my kWh cost are:
Off peak: $0.112 per KWh
Part Peak: $0.17 per kWh
So my average cost for charging 7hours off peak and 3 hours part peak is:
(0.112 x 7 +0.17 x 3)/10 = $0.13 per kWh
If you do 1000 mile per month the number of kWh per month is:
Miles per month / miles per kWh = 1000 / 3.89 = 257 kWh per month
Total electric charge per month = kWh per mth x $per kWh = 257 x 0.13 = $33.4 per month

Savings:
Saving over gas per month: 173.1 – 33.4 = $139.7 monthly saving
Note: If you want to be very precise you would also need to calculate the impact of changing electrical rates on your regular consumption which is a bit more complicated. In my case I did estimate that going from an E1 PG&E schedule to an E9A would increase my other electrical cost by $9 reducing my savings down to $131 / month

Other comparison of cost of gas versus electric:
Looking at the cost of doing 100 miles.
With a car doing 26 miles per gallon and a gallon costing $4.5
Cost of 100 miles on gas:
(Nb of miles / Mile per gallon) x $per gallon = (100 / 26) x 4.5 = $17.31
Cost of 100 miles on electric:
(Nb of miles / Mile per kWh) x $ per kWh = (100 / 3.89) x 0.13 = $3.34
Cost ratio gas (26 mil/gal) over Volt on electric:
Gas is 5.18 times more expensive than electric on the Volt
Note: this ratio varies depending on the price of gas in your area, your cost [per kWh, the number of miles you do on a single Volt charge.
Now let us do the same calculation with a 38 miles per gallon which is the estimated consumption of a Volt while running the electric motor using the gas engine.
Cost of 100 miles on gas at 38mpg: (100 / 38) x 4.5 = $11.84
Cost of 100 miles on electric (same as before) : $3.34
Ratio between operating the Volt on gas or on electricity: 11.84 / 3.34 = 3.54 times more expensive

Looking at MPGe:
Based on calculation at the top of this post
Kwh you get for the price of one gallon: price of a gallon / price of a kWh = 4.5 / 0.13 = 34.65 kwh
(From the Wikipedia article http://en.wikipedia.org/wiki/Miles_p...ine_equivalent


EPA use 33.7kwh as equivalent to one gallon, so I am not far off with my 34.65 kWh <> one gallon)
Number of miles you do on these kWh:
Kwh for the price of 1 gal x miles per kWh = 34.65 x 3.89 = 135 miles on electric for the price of one gallon (my MPGe)
If you take the EPA calculation, they use:
1 MPGE = 0.0292 miles per kWh
My calculation at the top show I get 3.89 miles per Kwh, so my MPGe is:
3.89 / 0.0292 = 133.2 MPGe again pretty close.

Now in the same Wikipedia page referenced above they say the Volt is given for 36kwh for 100miles or 94 MPGe this corresponds to doing 2.78 miles per kWh (100/36) or driving 30 miles on one charge of 10.8 kWh.
So actually conservative numbers

You can find an excel sheet with all these numbers and calculation so you can run simulation based on different gas price, miles on a charge, PG&E rates etc…
It has a simplified sheet and the full original sheet. On the original sheet are my full PG&E calculation which may be hard to figure out, but I left them there just in case
https://skydrive.live.com/?id=4BE668...e668230430efdd

Last edited by scrambler; 04-29-2013 at 02:50 AM.
scrambler is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old 04-27-2013, 09:37 PM
Member
 
TSquare's Avatar
 
Join Date: Mar 2012
Location: Nashville, TN
Posts: 35
I'm not going to check all your math but I did notice one thing.

"Base Parameters
Battery capacity: 16.5 kWh
My average miles per charge: 42 miles
As a result the number of miles I make on one kWh is:
Miles per charge / battery cap = 42 / 16.5 = 2.55 miles /kWh"


Your battery range of 42 miles is a good average, however it depends on weather and driving style, it could be anywhere from the low 20s to well over 50 miles per charge.

16.5 kWh capacity is correct but, you are only allowed to use about 10.5 of that before the generator starts. The battery has buffers built in at the top and bottom state of charge so that it can never be fully charged or discharged giving the main battery a very long life.

If you want to get into some lively discussions with other Volt owners come over to gm-volt dot com, a very active Volt forum.

2013 Crystal Red, D-2516
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

U235 Powered

Last edited by TSquare; 04-27-2013 at 09:41 PM.
TSquare is offline  
post #3 of 10 (permalink) Old 04-28-2013, 12:21 AM Thread Starter
Junior Member
 
Join Date: Apr 2013
Posts: 5
Thank you for pointing out that not all the 16.5 kwh are used. I had not caught that and it changes the whole thing significantly.

Researching what is the actual amount of kwh available before the battery is said to be depleted, I found an article that says they have an SOC of 30% which means only 70% is used or 11.55 kwh.

If that number is correct, then the MPGe is much better.

I have updated the original post and spreadsheet to reflect that and have the SOC as a variable so if we find out it is a different number we can update the numbers.

Last edited by scrambler; 04-28-2013 at 12:27 AM.
scrambler is offline  
 
post #4 of 10 (permalink) Old 04-28-2013, 06:54 AM
Member
 
TSquare's Avatar
 
Join Date: Mar 2012
Location: Nashville, TN
Posts: 35
You might want to check out voltstats dot net. There you can see the real world stats of over 1600 Volt owners. This site automatically pulls info directly from the car through Onstar twice a day.
My stats are here, https://www.voltstats.net/Stats/Details/2194

2013 Crystal Red, D-2516
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

U235 Powered
TSquare is offline  
post #5 of 10 (permalink) Old 05-30-2013, 02:40 AM
Junior Member
 
Join Date: May 2013
Location: Florida
Posts: 5
Cool MPGe

Quote:
Originally Posted by scrambler View Post
I recently decided to make the step to an electric car and of course chose a Volt as in my mind it is the best alternative today. It is the only one that gives you a full electric vehicle but with the safety net of not being bound by the charging possibilities.
Given the technology is still young, that interest rates are low and that lease incentives on this car is high, I went for a 36 month lease.
Prior to making the jump, I ran a number of calculations to figure out my gas savings so I tough I would share this data for those who may be looking.

But let us be clear, as far as I am concerned, the cost saving is just a Bonus when you use a Volt. The satisfaction is much bigger than just that part 

If someone catches any errors in my reasoning, please feel free to chime in. I also have a link to an excel sheet at the end so you can play with the numbers

Base Parameters
Battery capacity: 16.5 kWh
But as pointed by TSquare, there is an SOC of 34.6% so
Actual usable battery: 10.8 kwh
My average miles per charge: 42 miles
As a result the number of miles I make on one kWh is:
Miles per charge / battery cap = 42 / 10.8 = 3.89 miles /kWh

Cost of gas:
Let us say you have a car that makes 26 miles per gallon like mine did:
Let us say you drive 12000 miles / year or 1000 mile /mth
Take a price per gallon of $4.5
Your gas consumption per month is:
Miles per month / Mile per gal = 1000 / 26 = 38.5 gal per month
Cost of gas per month is:
Gal per month x $ per gal = 38.5 x 4.5 = $173.1 of gas per month

Cost of Electricity:
Now evaluating the cost of electricity for the car depends on a lot of things and it can be a bit complex. To simplify it, you can assume you will be charging mostly during off peak hours and some during part peak (if this is the rate system you choose), or an EV rate if you use a separate meter for the car. You need to figure out the kWh price for these rates, and make sure it includes all the costs.
For me I decided to start without a 240 volts charger, so my charging time is 10 hours
Off peak is only 7 hours per day (midnight to 7AM), so at best I can charge 7 hours off peak, and 3 hours on part peak.
I figured out that my kWh cost are:
Off peak: $0.112 per KWh
Part Peak: $0.17 per kWh
So my average cost for charging 7hours off peak and 3 hours part peak is:
(0.112 x 7 +0.17 x 3)/10 = $0.13 per kWh
If you do 1000 mile per month the number of kWh per month is:
Miles per month / miles per kWh = 1000 / 3.89 = 257 kWh per month
Total electric charge per month = kWh per mth x $per kWh = 257 x 0.13 = $33.4 per month

Savings:
Saving over gas per month: 173.1 33.4 = $139.7 monthly saving
Note: If you want to be very precise you would also need to calculate the impact of changing electrical rates on your regular consumption which is a bit more complicated. In my case I did estimate that going from an E1 PG&E schedule to an E9A would increase my other electrical cost by $9 reducing my savings down to $131 / month

Other comparison of cost of gas versus electric:
Looking at the cost of doing 100 miles.
With a car doing 26 miles per gallon and a gallon costing $4.5
Cost of 100 miles on gas:
(Nb of miles / Mile per gallon) x $per gallon = (100 / 26) x 4.5 = $17.31
Cost of 100 miles on electric:
(Nb of miles / Mile per kWh) x $ per kWh = (100 / 3.89) x 0.13 = $3.34
Cost ratio gas (26 mil/gal) over Volt on electric:
Gas is 5.18 times more expensive than electric on the Volt
Note: this ratio varies depending on the price of gas in your area, your cost [per kWh, the number of miles you do on a single Volt charge.
Now let us do the same calculation with a 38 miles per gallon which is the estimated consumption of a Volt while running the electric motor using the gas engine.
Cost of 100 miles on gas at 38mpg: (100 / 38) x 4.5 = $11.84
Cost of 100 miles on electric (same as before) : $3.34
Ratio between operating the Volt on gas or on electricity: 11.84 / 3.34 = 3.54 times more expensive

Looking at MPGe:
Based on calculation at the top of this post
Kwh you get for the price of one gallon: price of a gallon / price of a kWh = 4.5 / 0.13 = 34.65 kwh
(From the Wikipedia article http://en.wikipedia.org/wiki/Miles_p...ine_equivalent


EPA use 33.7kwh as equivalent to one gallon, so I am not far off with my 34.65 kWh <> one gallon)
Number of miles you do on these kWh:
Kwh for the price of 1 gal x miles per kWh = 34.65 x 3.89 = 135 miles on electric for the price of one gallon (my MPGe)
If you take the EPA calculation, they use:
1 MPGE = 0.0292 miles per kWh
My calculation at the top show I get 3.89 miles per Kwh, so my MPGe is:
3.89 / 0.0292 = 133.2 MPGe again pretty close.

Now in the same Wikipedia page referenced above they say the Volt is given for 36kwh for 100miles or 94 MPGe this corresponds to doing 2.78 miles per kWh (100/36) or driving 30 miles on one charge of 10.8 kWh.
So actually conservative numbers

You can find an excel sheet with all these numbers and calculation so you can run simulation based on different gas price, miles on a charge, PG&E rates etc
It has a simplified sheet and the full original sheet. On the original sheet are my full PG&E calculation which may be hard to figure out, but I left them there just in case
https://skydrive.live.com/?id=4BE668...e668230430efdd
Those calculations look sound. The calculations that I did before I bought my 2012 Volt were near the same but not as detailed. There were a few things that I did factor in that you left out which includes the price of maintaining the car (oil changes, etc.) which could alter my numbers a bit.

To summarize though what I came out was that I needed to drive about 12,000 miles per year for about five years to see the full pay off. I drove about 20K miles in the first year so I feel that I am well on my way. I also figured the increase in electric bill to be about $30 per month (full charge at least 5 days per week) and it ended up being exactly that.

Another cost trade off is no car payment versus a car payment if you are trading in an owned vehicle. I got <$4k for my trade in and pay $570/month. But considering the miles I use the vehicle I feel that I am quickly seeing the cost savings.

One important thing that the salesman doesn't point out is if you can't keep charging up your vehicle, you will need to keep putting gas in it. I had a lot of those weeks (putting gas in the car) because my former place of employment wouldn't let me charge up during the day and I would expend the entire Volt charge on the way to work in the morning. However, after a year of running this way, operating solely on gas, I am still getting better than 41.6 mpg. Seems good!

I'm still quite happy with the purchase. The car drives like a dream!
Worlock is offline  
post #6 of 10 (permalink) Old 07-10-2013, 12:05 PM
Junior Member
 
Join Date: Jun 2013
Posts: 3
Was going to raise the same topic myself
cartz80 is offline  
post #7 of 10 (permalink) Old 07-19-2013, 02:46 PM
Member
 
TSquare's Avatar
 
Join Date: Mar 2012
Location: Nashville, TN
Posts: 35
Quote:
Originally Posted by briando View Post
so my questions is, do you really save money with the volt over a straight gas car. somebody please answer this for me
It really depends on your daily driving habits and what kind of "straight gas car" you want to compare the Volt to. You can always find an inexpensive car with good gas mileage that would be hard for the Volt to beat on the cost of ownership. But, if you forget about the initial cost of the car itself and just compare the cost of driving, then the Volt can not be beat.
Personally, for me, I was driving a 2011 Malibu that was costing me about $200 a month in gas. I have had my Volt for 10 months now and I have not been to the gas station yet. I still have about 3 gallons of dealer gas in the tank. My daily commute is about 30 miles per day so I rarely burn any gas at all. I have gone from buying about 12 gallons of gas every week to buying maybe 7 or 8 gallons per year. Also, I now change the oil only once every two years instead of twice a year.
One other note to mention, when you drive a Volt with the gas generator running, you will be getting about 40 MPG.
Do I save money with a Volt? I would say yes.

2013 Crystal Red, D-2516
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

U235 Powered
TSquare is offline  
post #8 of 10 (permalink) Old 07-21-2013, 08:01 PM
Junior Member
 
Join Date: Mar 2012
Location: SE Michigan
Posts: 9
Quote:
Originally Posted by briando View Post
so my questions is, do you really save money with the volt over a straight gas car. somebody please answer this for me
Energy cost per mile absolutely!

There are not too many cars out there getting real world 76MPG lifetime average. My current total operating costs gas/electricity is 5.2 cents per mile driven.

I post stats on my blog;

http://home.comcast.net/~mi_volt/site/?/blog/
MI_Volt is offline  
post #9 of 10 (permalink) Old 09-09-2013, 11:13 PM
Junior Member
 
Join Date: Sep 2013
Posts: 1
Well, one other thing that helped sell me was the fact that its fast too. For an electric car even with four _large_ adults the thing gets up and moves. Is what pushed me over the edge. Sure it makes lots of financial sense... But it's also fun


Sent from AutoGuide.com App
efun is offline  
post #10 of 10 (permalink) Old 10-04-2013, 07:19 AM
Junior Member
 
Join Date: Oct 2013
Location: USA
Posts: 5
If you want to get into some vibrant conversations with other Voltage entrepreneurs come over to gm-volt , a very effective Voltage community. as a friend of mine is also been arguing and has been doing the conversations over there.

A motorhome is the best way to see the sights of Australia at your own pace!

Last edited by StevinStephan; 10-22-2013 at 06:29 AM.
StevinStephan is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Chevrolet Volt Forums: Chevy Volt Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome