You also need to add (9months*30days/mo*750Wh/day)/0.9 /(miles driven) to your number. For 10000 miles driven over the 9 month interval that would be 22.5Wh/mi. It's perhaps a slightly optimistic number as typically it's more like 1000Wh/day, but it depends. If you drive more, it's better, if you drive less, it's worse, of course.

1) Yes, that’s why I quote a minimum number for these cost calculations (no one does better than these numbers, unless they literally drive all the time...I guess technically if you drive 16 hours a day you might end up with a mile per day). But 3% of the time spent driving is more typical. So 3 miles a day, just like Tesla says, is the minimum, for the long-haul drivers it might be 2.7 miles per day minimum

I take what I paid on my bill and divide by Kilowatt hours used and end up with .093 per Kwhr. So that includes all fees etc.
Previously I would only put Shell 93 Octane in my dino car so I’m saving a lot. I logged my usage in Fuelly so I actually have data. I logged my WRX for about a year.

I take what I paid on my bill and divide by Kilowatt hours used and end up with .093 per Kw/hr. So that includes all fees etc.
Previously I would only put Shell 93 Octane in my dino car so I’m saving a lot. I logged my usage in Fuelly so I actually have data.

That ensures you are not UNDER-estimating the cost of running an EV. However, if there is a monthly meter fee or other expense that would be there regardless of whether you had an EV or not, you need to back those fixed expenses out before dividing by the kWh. Since you are going to have electric service regardless of what you drive, the monthly meter fee (if any) shouldn't factor in (unless you have a meter dedicated to EV charging).

Just to add my 2c, I see several of you using power cost estimates of 20 or even 30 cents per kwh. I would say that vast majority of those who live in the USA do not or should not be paying that much. My rate is 10 cents. I get it that in Hawaii the rate is 35+ cents per kWh, but if you live in Hawaii you really should get solar panels installed, sign up for time of use metering, etc.

I just spend a couple of weeks on Oahu, and I was talking to a guy who could not afford to pay for solar upfront, so he signed a solar lease and is paying 15 cents. I get it that there are those who rent, live in an apartment, etc. But those who rent, AND live in the area with very high electric rates only represent a small percentage of Tesla owners. And some of them should still be able to get time of use metering.

I agree Ivan. I pay 9.5 cents p kw. But there is a monthly 7 dollar minimum per month change in addition the 9 and a half cents per. Here in New England we have Eversource. They don’t have off peak hours anymore which sucks. I used to sell solar and had my house surveyed and I don’t get enough sun. Bottom line is it costs much less to drive my M3 than an ice car.

Since we generally compare ICE vehicles on a gas mileage basis, I created a simple Microsoft XLXS based model in which you input three things:

A) the kwh/mi you are getting (read from the display in your vehicle),
B) the price of a kwh of electricity in your area (include taxes, fees, etc. from your electric bill) in $ format,
and
C) the price of gasoline in your area (need to decide if comparing to regular, premium or ???) in $ format.

For those who are interested, the formula (using the above letters) is:

(A x B)/1000 or A times B divided by 1000 = Cost per mile driven in EV

Then divide C by the above result. The output is the equivalent gas mileage.

For example, my readout is typically around 275 kwh/mi and the price of electricity at my place is around $0.15 per kwh. So my cost per mile is 275 x $0.15 = 41.25. Divide by 1000 = $0.04125. (a little over 4 cents per mile.)

Per the Gas Buddy app, gas in my locale is currently around $2.70 for Regular and $3.25 for Premium

Divide $2.70 by $0.04125 and the result is an equivalent cost of 65.5 mpg on Regular

Divide $3.25 by $0.04125 and the result is an equivalent cost of 78.8 mpg on Premium

For those who are mathematically challenged, I tried to upload the file but the system will not permit me, "The uploaded file does not have an allowed extension."

This allows direct comparison to your buddies who are driving dinosaurs - AND I STILL HAVE ONE

I agree Ivan. I pay 9.5 cents p kw. But there is a monthly 7 dollar minimum per month change in addition the 9 and a half cents per. Here in New England we have Eversource. They don’t have off peak hours anymore which sucks. I used to sell solar and had my house surveyed and I don’t get enough sun. Bottom line is it costs much less to drive my M3 than an ice car.

Your generation charge might be 9.5 cents, but your distribution charge (which includes the $7 customer charge you mention) adds another 13 cents or so. I live on the Cape, not far from you. I am also an Eversource customer. My February bill shows 22.34 cents per kWh. That's 9.2 cents for generation and 13.14 cents for distribution. I'd quote my March bill, but I have solar panels and a net meter, so I am not paying a March bill. Unfortunately MA has the fourth highest average electric rate in the Nation. Only Hawaii, Alaska and Rhode Island are higher. I previously posted a link to the average electric rates.

Using the link above, one can see the average January 2019 electric rates by state. If you read a post wherein someone has posted a rate significantly different, there is a reason, i.e. solar panels (my case), off hour rate (not offered in my area), generation charge only, etc; and that reason should be included in the post. After all, this forum is intended to support, not mislead (i.e. things like $1.16/kWh or 70 amps minimum for charging an EV). As for Super Charging, those who have to pay can assume TESLA will charge above their billing rate (I don't know what it is in MA, but I would guess 24-30 cents). Lucky those who live in states with low electric rates (makes them good candidates for EVs).

I agree Ivan. I pay 9.5 cents p kw. But there is a monthly 7 dollar minimum per month change in addition the 9 and a half cents per. Here in New England we have Eversource. They don’t have off peak hours anymore which sucks. I used to sell solar and had my house surveyed and I don’t get enough sun. Bottom line is it costs much less to drive my M3 than an ice car.

It's amazing how much difficulty people have, and bandwidth is spent, on this question.
Calculate the marginal cost. If tiers are involved then it gets a bit more messy but is no more difficult than calculating taxes when brackets are involved.

E.g.

I paid 34.61 + 8.13 + 3.19 for 444 kWh
1.097395x was added in taxes and for the energy savings program

Total: 45.93*1.097395 = $50.4 for 444 kWh = 11.35 cents a kWh

---
My car's lifetime Wh/mile is 217 Wh per mile so my battery to wheels cost is
11.35*0.217 = 2.46 cents per mile

I guess that meter to battery has ~ 12% losses so my meter to wheels cost is
2.46/0.88 = 2.8 cents per mile

It's amazing how much difficulty people have, and bandwidth is spent, on this question.
Calculate the marginal cost. If tiers are involved then it gets a bit more messy but is no more difficult than calculating taxes when brackets are involved.

As fuel prices fluctuate, differing regions of the country have different prices, I can only share my current experience. Sold 2015 Lexus is250 prior to receiving my Mod 3. I would fill the Lexus weekly for an approximate of $35 (Half tank at $3.12-$3.54. $35 x 4 weeks = $140. I currently charge my Mod 3 twice weekly, usually for 2-2.5 hrs. I drive 36 miles round trip to work, daily. 36 x ~20 days = 720 miles/mos. Here's where the calculations get squirrelly. First 350 kWhr = 10.68 cents. Next 850 kWhr = 12 cents. Over 1,200 kWhr = 14 cents. Without boring you with all the details and math,(I hate math and it hates me!), I'm spending approximately $48/mos according to my breakout on the electric bill. I compared previous 3 mos bills (Winter) in Hawaii (cooler, less A/C) and looked at my difference. So, savings over fuel for ICE = $92. (Don't check my math because math hates me!) That said, I am having a Tesla 2 Power Wall installed at the end of the month (More Fed/State Refunds!) and when it is completed, I will charge my vehicle for...wait for it....FREE! (Yeah, I know! Hey Groovidad, how about the cost of the system?) Yes, yes true yet, not only will I have the power daily to charge the Mod 3, I can use the backup in the evening to run lights, fridge, A/C, yadda, yadda AND whenever there is a power outage. My dad once said, "Go big or don't go at all, son!" So, based on my fathers words of wisdom, I'm going big, "Green big", that is!
Sorry! I neglected to add in the increase in property value! Here in the Aloha State, Solar is "IN"!!

It's amazing how much difficulty people have, and bandwidth is spent, on this question.
Calculate the marginal cost. If tiers are involved then it gets a bit more messy but is no more difficult than calculating taxes when brackets are involved.

I paid 34.61 + 8.13 + 3.19 for 444 kWh
1.097395x was added in taxes and for the energy savings program

Total: 45.93*1.097395 = $50.4 for 444 kWh = 11.35 cents a kWh ??
$58.27/444=$0.013.13/kWh
---
My car's lifetime Wh/mile is 217 Wh per mile so my battery to wheels cost is
11.35*0.217 = 2.46 cents per mile

I guess that meter to battery has ~ 12% losses so my meter to wheels cost is
2.46/0.88 = 2.8 cents per mile

i've had my MR for about 3 weeks now and haven't crunched any numbers (mostly due the fact that I'm still trickle charging and haven't set up a nema 14-50 in the garage yet). I'm still waiting on my electric bill for this cycle to see how much of a difference charging at home has been to the bill

I'm charging at work too for the time being so i guess that's considered free charging and the occasional supercharge

i've told most people that its at least half the cost of an ICE car and they are already impressed (except the hybrid drivers...)

I have a Prius Hybrid. My Model S85D electric use beats it easily. Just a little over a quarter (27%). Prius @ 55 MPG with gasoline at $2.60/Gal. MA has the fourth highest electric rate in the 50, but I have solar panels.

The formula
1. Get the cost of gas per gallon. G
2. Get your lifetime Wh/mi from the car (at least one trip metre must never be reset to obtain this figure). W
3. Get your electricity rate by dividing the amount you pay on your electric bill by the number of kw used during the billing period. P
4. Estimate 15% charging losses. K
5. Total mi/kw. M
6. Total cost of electricity. $
7. Total kw used per mile. T
8. Cost per mile (electricity). C
9. Dimes in a mile. D
10. Number of dimes in a gallon of gas. N
11. Equivalent mpg to match electric. E

W + (W * K) = T
245W + (245W * .15K) = 281.75T
1000 / T = M
1000 / 281.75T = 3.549M miles/kw
P / M = C
0.072P / 3.549M = $0.2029C cost per mile
$ / C = D
1$ /.2029C = 4.9285D dimes per mile
G / $ = N
3G / .10$ = 30N dimes per gallon
N * D = E
30N * 4.9285D = 147.86E mpg to be the equivalent of electric.

This works but is kind of involved.

Instead round the numbers.
Find the number of dimes used electrically
Find the number of dimes in a gallon of gas
Multiply to get the mpg equivalent.
0.072P ~= 0.10P
245W ~= 250T
1000 / 250T = 4D
30N * 4D = 120E

I have a Prius Hybrid. My Model S85D electric use beats it easily. Just a little over a quarter (27%). Prius @ 55 MPG with gasoline at $2.60/Gal. MA has the fourth highest electric rate in the 50, but I have solar panels.

I'm surprised you're able to get 300Wh/mi in your S85D (I thought it was rated 330Wh/mi?). You stated average rate of 4.3cents/kWh earlier I think? 4.3c/kWh*300Wh/mi = 1.29 cent/mi = 27% of 4.7 cents/mi (Prius)

Anyway.

You are definitely in an area where if the sole objective is to save on energy costs for your vehicle, you'd want to get a large solar array first!

Sadly without massive solar arrays in San Diego, they've moved around the time-of-use hours to minimize the benefit of solar. They do offer good TOU plans (with a small monthly fee to get about 9 cents/kWh at night), but when you move to that plan, then you had better not use AC between 4-9PM in the summer (at 50 cents/kWh). If you didn't get forced into the TOU by your quest for cheap EV charging, you could get either a tiered rate (which would usually be much better but depends on your use) or a different TOU rate plan which provides for twice as expensive (17 cents) nighttime charging, but 27cents/kWh for most AC use, up to a point - so giving up those cheaper AC rates (if you use AC) could be an extra cost of owning an EV if you pay for the the ultra-cheap night rate! It's a dizzying optimization problem and I think there are about 5 main obvious plans to choose from, but I think there are something like 20 different rate plans available.
The solution is to go big or go home on your solar - 8kW should support 1 EV fairly well, as long as you don't use much AC. If you have two Teslas a 10-12kW system could be more appropriate. Obviously all depends on how much driving you do. I'm adding in some margin on the solar sizing here because the last thing you want to be doing is to put a bunch of money into solar and then have to pay through the nose for TOU AC use. Figuring out the exact right optimum is pretty impossible without knowing the exact usage patterns. And also affected by whether you can get a west-facing array.

The short formula on the bottom of the original post should account for those as well. Vampire drain doesn't appear to be much, nor does the time spent in park (for me YMMV). I guess it would be considerable if I frequented drive-in movies (yes, there is one around where I live).