Simple formula to calculate "fuel" savings (miles required)

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mbender

Well-known member
Joined
Apr 21, 2013
Messages
824
Location
The Great California Delta, and environs
So, I was wondering how many miles I have to drive to "earn" $1000 compared to driving my old (or any) ICE. And here's what I came up with to estimate it, a bit more generalized:
Code:
                               T
                ------------------------------
M  ==                 ppg            ppkwh          ,  where M = miles required to recoup the target $T,
                 (   -----    -     -------   )
                      mpg            mpkwh                               and...

ppg = price per gallon of the petro-fuel for the ICE           ppkwh = price per kWh paid for electricity
mpg = miles per gallon that the gasser/ICE gets                mpkwh = miles per kWh that you get in the EV/LEAF
So, to "make" $1000 by driving a LEAF vs an ICE, you might get the following range:

------------> High end (drive LEAF hard, high electric rate, replace Prius when gas price is low):
------------> M = 1000 / ($3.00/50 - $0.15/3) = 100,000 miles

------------> Low end (drive LEAF gently, low electric rate, replace 25-mpg ICE when gas price is high):
------------> M = 1000 / ($4.00/25 - $0.09/4.5) =~ 7,150 miles

Quite a range of 'miles-for-savings', depending on all four of the variables (as we all know).

I have to drive about 12,000 miles to make $1000 over my old ICE at $3.50/g. Here's to high gas prices in the future, LOL.

ps. Sorry if the code formatting doesn't work on all screens. I'll replace with an image if necessary.
 
Neat. I get 14500 miles by using my electric rate ($0.05) and my old car (45mpg).

I'm definitely not saving any money. But I like the experience and I feel like I'm making a difference. Maybe.
 
mynameisjim said:
Neat. I get 14500 miles by using my electric rate ($0.05) and my old car (45mpg).

I'm definitely not saving any money. But I like the experience and I feel like I'm making a difference. Maybe.
Hey, $1000 per year or even two is nothing to sneeze at! I'll take it, anyway. ;-)

As for 'making a difference', you are... we all are. Who was it who said, "There are no inconsequential actions -- only consequential ones." ?

ps. $0.05 per kWh?? Many of us can only dream of that price!!
 
My other car is a Tundra. I get 15mpg. If you assume gas is $3 a gallon, and that it costs 5 cents a mile to drive the Leaf, and that I drive 300 miles a week (and I do, and then some, usually), I am saving $45 a week in gas.

My car payments are $459 per month, before receiving my federal and state rebates. 4 x $45 is $180.

I estimate that the rebates will give me between $186 and $293 per month in payments, depending on how the state incentive is eventually calculated.

So, it pretty much pays for itself, aside from the increase in my insurance payments.
 
Thanks for the formula. I'm on the low end, just about exactly what you estimated except I pay $0.06/KWh. I drive about 7000 mi/yr, so saving around $1000/yr. Even over the next 10-15 yrs of ownership, I have my doubts whether there will be any real $ savings over my old ICE. However, it's difficult to $$ quantify the difference in driving experience between a 20 yr old ICE and a new EV.
 
Reddy said:
Thanks for the formula. I'm on the low end, just about exactly what you estimated except I pay $0.06/KWh. I drive about 7000 mi/yr, so saving around $1000/yr. Even over the next 10-15 yrs of ownership, I have my doubts whether there will be any real $ savings over my old ICE. However, it's difficult to $$ quantify the difference in driving experience between a 20 yr old ICE and a new EV.



Recheck your math. I "pay" $0.08/KWh but when I divide the total electrical bill by the total KWh consumed it comes to almost $0.20 !!!

In my case the Leaf costs about 1/3 per mile than the car it replaced when only the "fuel" cost is considered.
 
PV2leaf said:
Recheck your math. I "pay" $0.08/KWh but when I divide the total electrical bill by the total KWh consumed it comes to almost $0.20 !!!

In my case the Leaf costs about 1/3 per mile than the car it replaced when only the "fuel" cost is considered.

Your point that there is more to electric costs than just the energy charges is well taken, but I think you should take the electric bill you had before using any power for LEAF and compare to the bill after using power for LEAF. All of the other fees and charges were there before the car, so why attribute them to the car?
 
kikngas said:
PV2leaf said:
Recheck your math. I "pay" $0.08/KWh but when I divide the total electrical bill by the total KWh consumed it comes to almost $0.20 !!!

In my case the Leaf costs about 1/3 per mile than the car it replaced when only the "fuel" cost is considered.

Your point that there is more to electric costs than just the energy charges is well taken, but I think you should take the electric bill you had before using any power for LEAF and compare to the bill after using power for LEAF. All of the other fees and charges were there before the car, so why attribute them to the car?


My point is that even though your bill says are paying a certain amount per KWh the taxes and fees can double that amount. The other fees are all percentage of KWh used I have not seen any leveling of any of the many fees. (Think "all this for $19.99*" ..................... *plus $18.00 Shipping & Handling and applicable sales tax!)

In my case I have a flat interconnect fee of $16.00 a month for having my PV system on net metering, so they are taxing me 80 KWh of production a month for the use of the grid as a "storage bank". I supply them power during the day when it most in demand and I pull it at night ( I also charge at night). As for the before and after ... we used to run electric heaters from December to March in the bedrooms at night to consume the surplus power as the check we would receive in March would be at wholesale rates and come with a 1099. Since the Leaf we don't have the large surplus and usually have a modest bill January through March that is less than a tank of gas.

No one should expected it to be free and even if you have access to free charging that ride will also eventually end.
 
My '96 Jeep Cherokee typically gets around 23 mpg and gas around here is currently $2.999/gallon. I have solar so I don't pay anything (additional) for electricity, so my mileage efficiency in the LEAF (currently 4 miles/kWh from the wall) is irrelevant.

So, ($1000/$2.999) x 23 = 7669 miles to save $1000

Never actually thought about it that way.

Nevertheless, the LEAF isn't remotely cost effective for me since its cost was high — especially compared to just driving the old Jeep — and my annual LEAF mileage is low, about 7400 miles per year. Saving money wasn't the point of buying the LEAF.
 
mynameisjim said:
Neat. I get 14500 miles by using my electric rate ($0.05) and my old car (45mpg).

I'm definitely not saving any money. But I like the experience and I feel like I'm making a difference. Maybe.


HOLY CRAP 5 cents/kWh!!!!

I pay 30 cents at max tier (California). I need to switch to Time of Use.
 
I had no idea so many would be jealous of my electric rate. I pay 5.85 overnight, 10.1 off peak, and 37 peak. I had to install a new meter for this program.
 
Yup, SoCal rates are between $0.35 and $0.41 kWh at peak times, which I see daily with regular use of the L1 charger. Overnight charges are much lower...around $0.18 kWh. Gasoline is only $3.20 per gallon.

Regardless, I pay about $40-55 per month to commute 40 miles per day.
 
I guess I have it somewhat lucky. Flat $.11 all day every day. I looked at the TOU difference and it just wouldn't have saved money as it tripled during the day but then only went down 1/3 during off hours.
 
I'm in a weird middle.

I go anywhere from 30MPG in my ICE car, and 25-50MPG on my motorcycles. I get about 5.0mi/kWh in the Leaf (probably closer to 4.6 if talking about grid power). Each has its own uses.

Using 4.6… 10k miles costs about $220
Car, about 1150, depending on gas prices
M1 is about $1800, and M2 is $700

That means I can save $1k in as few as 6300 miles. I don't always zip around on my motorcycle though. Add in the cost of oil and tires, and that motorcycle gets even more expensive.

I didn't buy the Leaf to save money. I bought an electric car for energy independence. A 1kW solar system would be enough for 100% solar powered Leaf. Sadly, I rent, so no solar. Hopefully this is changing soon…
 
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