Estimated gas savings

[mknox]

I did my own calculations based on the car I was replacing. Sure I could have bought a newer ICE that got better mileage, but I thought it was a good starting point. I just re-visited my numbers after two years of Model S ownership:

Former ICE:
23,000 miles/year @ 21 MPG (my 4 year average with that car) * $4.54/gallon = $4972.38 (I based it on $1.20/liter here in Canada and converted to US gallons even though Regular is now around $1.09, but the ICE needed Mid-Grade)

Model S:
My average all-in consumption, including vampire and charging losses = 447 Wh/mi for the past 2 years (I meter or record all energy going into the car. The car's own display way underestimates the actual energy that the car consumes)

23,000 miles/year * 0.447 kWh * $0.1215 (my off-peak rate) = $1,249.14

Difference = $3,723.24 per year (or $310.27/month)

I'm probably a lot better than that because a significant percentage of my charging is done at public or workplace stations (incl. the odd Supercharger) where I don't pay anything for the electricity. My assumption above was that all electricity going into the car was paid for by me. No one ever gave me free gasoline, so the ICE numbers are pretty solid.

 

[dirkhh]

To state the obvious and keep it simple: 200,000 miles @ 25mpg @ $4/gallon = $32,000.

Number to be adjusted by home charging costs (10%-20% depending on home/SC mileage split and cost of electricity), actual mileage of ICE being compared, and higher/lower average cost of premium gasoline over the period. In most cases, at least half of that will be achieved.

4 bucks a gallon? Not this year. Below $2.50 wherever I look...

 

[CHGolferJim]

.......over the period......

 

[mibaro2]

I did my own calculations based on the car I was replacing. Sure I could have bought a newer ICE that got better mileage, but I thought it was a good starting point. I just re-visited my numbers after two years of Model S ownership:

Former ICE:
23,000 miles/year @ 21 MPG (my 4 year average with that car) * $4.54/gallon = $4972.38 (I based it on $1.20/liter here in Canada and converted to US gallons even though Regular is now around $1.09, but the ICE needed Mid-Grade)

Model S:
My average all-in consumption, including vampire and charging losses = 447 Wh/mi for the past 2 years (I meter or record all energy going into the car. The car's own display way underestimates the actual energy that the car consumes)

23,000 miles/year * 0.447 kWh * $0.1215 (my off-peak rate) = $1,249.14

Difference = $3,723.24 per year (or $310.27/month)

I'm probably a lot better than that because a significant percentage of my charging is done at public or workplace stations (incl. the odd Supercharger) where I don't pay anything for the electricity. My assumption above was that all electricity going into the car was paid for by me. No one ever gave me free gasoline, so the ICE numbers are pretty solid.

Nice numbers.
I wish the model S had a way of keeping track of how much energy we used when charging at public chargers/superchargers. That way we could see how many kw we got for free over the life of the car. Right now we are just guestimating how often we charge for free (at least I am...never was great at keeping those scraps of paper with before and after numbers).

 

[mknox]

4 bucks a gallon? Not this year. Below $2.50 wherever I look...

Yeah, but as I mentioned, I am in Canada. Today, Regular is running $1.099 a liter in my area which works out to $4.16 a US gallon without doing any $CDN to $US conversion. Our higher gas prices make the EV economics a little more favorable. :wink:

EDIT: I see you were referencing @CHGolferJim, but I used $4.54 in my numbers too!

- - - Updated - - -

I wish the model S had a way of keeping track of how much energy we used when charging at public chargers/superchargers.

Agreed, but there's even more to it than that. When you plug in, not all of the energy coming out of the wall makes it into the battery. There are efficiency losses in the on-board charger, power needed to run the cooling pumps and fans and even in the process of converting electrical energy to chemical energy in the battery. When the car is idle, there are the famous "vampire" losses as well. A gas car analogy would be having a car with a slow leak in the gas tank and then also being sloppy and spilling gas at the pump. The gas pump doesn't care how much fuel spilled out on the floor just as the electricity meter doesn't care what happens to the electricity after it passes through it.

I wish the Model S tracked how much energy goes into the charge port. That would be a true reflection of how much power (and cost) is involved in operating the car.

FWIW, I keep a spreadsheet documenting all of this. I have a dedicated meter on my plug at home, I use Smart Meter data to see how much I use at work (I work for an electric utility and have access to these systems), I download any ChargePoint data, note the kWh input at Superchargers and keep a log of use at other stations.

 

[CHGolferJim]

Mknox, is there a rule of thumb on the % loss you refer to? (in order to calculate how much to gross up the usage shown in the car?) Thanks.

 

[mibaro2]

Agreed, but there's even more to it than that. When you plug in, not all of the energy coming out of the wall makes it into the battery. There are efficiency losses in the on-board charger, power needed to run the cooling pumps and fans and even in the process of converting electrical energy to chemical energy in the battery. When the car is idle, there are the famous "vampire" losses as well. A gas car analogy would be having a car with a slow leak in the gas tank and then also being sloppy and spilling gas at the pump. The gas pump doesn't care how much fuel spilled out on the floor just as the electricity meter doesn't care what happens to the electricity after it passes through it.

I wish the Model S tracked how much energy goes into the charge port. That would be a true reflection of how much power (and cost) is involved in operating the car.

FWIW, I keep a spreadsheet documenting all of this. I have a dedicated meter on my plug at home, I use Smart Meter data to see how much I use at work (I work for an electric utility and have access to these systems), I download any ChargePoint data, note the kWh input at Superchargers and keep a log of use at other stations.

And wouldn't it be so much easier if the car just kept track of it all, accurately?
I wish I had put a meter on my 14-50 outlet in my garage when it was installed. But never thought of it.

 

[exLeaf]

Former ICE:
23,000 miles/year @ 21 MPG (my 4 year average with that car) * $4.54/gallon = $4972.38 (I based it on $1.20/liter here in Canada and converted to US gallons even though Regular is now around $1.09, but the ICE needed Mid-Grade)

It is such a delight to see that you decided to dump your gas guzzler. Wonder if there is somewhere stat what people dump to get Tesla and join efficient car market.

 

[mknox]

Mknox, is there a rule of thumb on the % loss you refer to? (in order to calculate how much to gross up the usage shown in the car?) Thanks.

Well, I just looked at 24 months of my useage and see that the car's Lifetime Wh/mi is saying 343 while my calculated actual is 447. That is a bit over 30% difference. This could vary quite a bit based on your driving patterns. I have a daily 90 mile round trip commute and use the car quite a bit which would tend to lower the variance. If the car sat longer (more vampire losses) or was driven shorter distances (more losses associated with battery and cabin heating in the winter), the spread could be larger.

 

[CHGolferJim]

And you have an older car and Canadian winters which both exacerbate it?
What would you guess would hold in North Carolina with a new 70D?

 

[mknox]

It is such a delight to see that you decided to dump your gas guzzler. Wonder if there is somewhere stat what people dump to get Tesla and join efficient car market.

For me, the fuel cost savings was a significant factor in my decision. My former car was a Cadillac CTS which I very much liked, and I may have simply replaced it with a newer model. But when I ran my numbers, the Tesla (even though much more expensive to purchase) worked out to a similar TCO. I have always like the idea of using locally produced energy vs. imported fuel (I do work for an electric utility) and am also kind of a tech geek and like jumping on new technologies. All the stars aligned for me around the purchase of a Model S.

- - - Updated - - -

And you have an older car and Canadian winters which both exacerbate it?
What would you guess would hold in North Carolina with a new 70D?

I don't think the older car has any bearing. I easily see 260 Wh/mi on my daily commute which is about 75% freeway at 70 or more MPH. (300 Wh/mi is approximately Tesla's Rated number, so I'm easily beating that). The winters? Yes. One thing the Tesla is good at is its thermal management. I will see a huge spike in energy as I set out, but as all of the systems get up to temperature, my consumption goes down to near summer levels making my overall trip come in at maybe 20% more than I see in summer. On the winter weekends, when I make many short trips around town, I may see consumption 400% higher than summer! That's because the car never gets a chance to warm up before it cools down again.

I would not underestimate the charging losses and standby losses if you truly want to know how much your car is costing to operate. My 30% may be a bit conservative in your environment, but then your driving patterns may make it such that it's not that far off. It will definately be more than the car's display shows you. The display only seems to track the energy that comes out of the battery when the car is on and running.

 

[CHGolferJim]

Appreciate your perspective, one few others have.

 

[lphe]

I did my own calculations based on the car I was replacing. Sure I could have bought a newer ICE that got better mileage, but I thought it was a good starting point. I just re-visited my numbers after two years of Model S ownership:

Former ICE:
23,000 miles/year @ 21 MPG (my 4 year average with that car) * $4.54/gallon = $4972.38 (I based it on $1.20/liter here in Canada and converted to US gallons even though Regular is now around $1.09, but the ICE needed Mid-Grade)

Model S:
My average all-in consumption, including vampire and charging losses = 447 Wh/mi for the past 2 years (I meter or record all energy going into the car. The car's own display way underestimates the actual energy that the car consumes)

23,000 miles/year * 0.447 kWh * $0.1215 (my off-peak rate) = $1,249.14

Difference = $3,723.24 per year (or $310.27/month)

I'm probably a lot better than that because a significant percentage of my charging is done at public or workplace stations (incl. the odd Supercharger) where I don't pay anything for the electricity. My assumption above was that all electricity going into the car was paid for by me. No one ever gave me free gasoline, so the ICE numbers are pretty solid.

I would be very interested to see how kWh / mi energy consumption varies based on the season. Have you computed the kWh/mi for each month of the year, or each season. I would expect kWh/mi to be significantly greater in the winter vs. the summer.

 

[mibaro2]

Here is a chart I put together for my first year of driving the model S. The first month's numbers are not normal since I was showing off the car a lot and enjoying the quick starts.
You can see the spike in wh/km start in November and go until February.

 

[lphe]

Here is a chart I put together for my first year of driving the model S. The first month's numbers are not normal since I was showing off the car a lot and enjoying the quick starts.
You can see the spike in wh/km start in November and go until February.

Thank you for your reply. Are the kWh's that you are using reported by the car or do you meter the actual electricity consumed by the car from the power company?

 

[mibaro2]

Thank you for your reply. Are the kWh's that you are using reported by the car or do you meter the actual electricity consumed by the car from the power company?

It is reported from the car. (which as MKnox pointed out is not 100% accurate).

 

[lphe]

It is reported from the car. (which as MKnox pointed out is not 100% accurate).

So apparently it takes 268 (feb) / 172 (jul) = 1.55 times as much energy in the winter vs. the summer to drive the car, i.e. range is reduced by this factor. I assume you use the heater in the winter. Do you also remote start or precondition the car in the winter before starting out? Do you generally leave the car plugged in all the time during the winter?

 

[mibaro2]

So apparently it takes 268 (feb) / 172 (jul) = 1.55 times as much energy in the winter vs. the summer to drive the car, i.e. range is reduced by this factor. I assume you use the heater in the winter. Do you also remote start or precondition the car in the winter before starting out? Do you generally leave the car plugged in all the time during the winter?

I would preheat the car in the morning using shore power for about 15-20 minutes. When leaving work I would preheat the car for 10 minutes using the battery.
I generally plug in the car every night in my garage throughout the year and charge at 38amps. I have the start time for the charge set so that it is just finishing as I am leaving. Yes, I use the cabin heater, but generally on a low setting since the car is preheated.

 

[lphe]

Has anyone analyzed in some thread why it takes so much more power in the winter to propel the car? I observe for my car that it takes 40% more energy for the commute to work in the winter vs. the summer even with the heater off. When it is below 0 F, it takes more than three times as much power when when I first start out vs. the amount of power required in the summer to go 30 mph. Is that also true of the Model S? There must be a lot more friction when it is cold. But even when the bearings, transmission, and other sources of friction warm up, the extra power required in the cold seems to be a lot higher than the 15% more predicted by denser air or tire rolling resistance. Maybe someone is aware of a thread that discusses this further.

 

[SeminoleFSU]

You guys in the US make us in the UK and Europe cry with your gas prices for $4 and less.
We get gas prices more like $9 although it has reduced a bit now to $7.5-$8

Best thing about that is it does make the Tesla maths much easier especially when you do 25K miles/yr

Add in the 8yr drivetrain warranty and happy motoring ... well when the delivery wait is over anyway.

That's the benefit of having the world's reserve currency. Don't worry though we are running huge debt increases year over year devaluing the dollar until the point when no one will want to use it anymore. At that point our special American crude oil prices will be history.