Calculating Charging Cost at Home

[Pstreicher1]

Newbie here. Got my 2021 Model X on December 10th, 2020. No problems found luckily and having a ball driving now. I am finding a new way to drive thanks to the electric motors making things quick. Not to mention the nice road handling and so much else.

So, after many charges now, about every two days using the Wall Connector at 47 amps and 240 volts.Tonight I decided there must be a way to put some formulas into a spreadsheet to figure out how much it is costing me to charge.

Tampa Electric or TECO as it's called (a Duke Energy company) charges the below amounts as of my 12/09/2020 billing.

Base charge of $15.05 / kWh

Energy charge of $0.05375 / kWh
Fuel charge of $0.02285 / kWh

Total of the last two is $0.0802/kWh.

Using P=I*E
P=? (kWh)
I=47
E=240
(Not at all sure about the above)

Now how do I complete and or correct this formula to get my total cost to charge
the 165 miles needed to get to the top charge of 334 miles as shown after each full charge?
I haven't used electrical formulas in a long time and I am so confused by it now.
Can anyone shed some light on this for me and maybe other members here?

Thanks in advance,
Paul in Tampa

 

[SageBrush]

Welcome, and congrats on your new car

Using P=I*E
P=? (kWh)
I=47
E=240

I = Amps = 47
V = Volts = 240
P = Power = I*V = 47*240 watts = 47*0.240 kW

E = Energy = P*hours = kWh
Unless you know how much time you charge, none of this helps you.

---
The card in the bottom left of the screen has distance traveled and kWh/mile. The product tells you the total kWh consumed during travel (which does not include ~ 12% charging losses or car vampire losses.)

Your utility has these marginal energy charges

So either 5.495+3.336 cents per kWh or
6.495+4.361 cents per kWh

Example:
Say you drove 1000 miles at 0.35 kWh per mile. That works out to 350 kwh
At the higher marginal cost of 10.856 cents per kWh you spent 358*0.10856 = $38.86 to move the car 1000 miles
Including charging losses of ~ 12% you spent 38.86/0.88 = $44.16
Vampire losses vary (it's a long story) but 0.5 kWh a day is ballpark

---
By the way, since your charging setup at home puts ~ 10 kWh into your battery per hour and your battery capacity is ~ 100 kWh, each hour of charging at home is ~ 10% battery charge increase.

 

[michaelnorbert]

get teslafi and input your "all in" kwh price, you will see how much you're paying.

 

[SageBrush]

get teslafi and input your "all in" kwh price, you will see how much you're paying.

I don't recommend it due to the multiple complaints of much higher vampire losses

 

[dhrivnak]

If you really want to know, i would get a meter for about $15 on eBay. I have installed 3 to track car and HVAC usage and they have worked well for me. 100A AC LCD Panel Digital Power Watt Meter Monitor Voltage KWh Voltmeter Ammeter | eBay

 

[michaelnorbert]

I don't recommend it due to the multiple complaints of much higher vampire losses

i'm not seeing the app causing vampire losses, car is always sleeping at home when it's not being charged.

 

[house9]

I don't recommend it due to the multiple complaints of much higher vampire losses

When configured properly TeslaFi can almost eliminate all vampire drain (at least in my limited experience)

The problem is it isn’t configured to do so by default.

Is Phantom drain a hoax?

 

[SageBrush]

When configured properly TeslaFi can almost eliminate all vampire drain (at least in my limited experience)

The problem is it isn’t configured to do so by default.

Yes, I'm under the same impression. I figured OP has enough new things to learn for now; and it would be difficult for even those comfortable with the trivia of running an EV to separate out vampire drain from overall consumption.

KISS (keep it simple, smarty)

 

[Puma2020]

Base charge of $15.05 / kWh

Are you sure that is for each kWh?

I suspect that is $15.05 base charge just to be connected to the grid.
Then $0.0802/kWh for every one kWh you pull, which I would think would be great. We pay about $0.15/kWh up here in NH.

After that it all depends on how you drive and how far far.
Your Wh/mi value is the important metric.
let's say you get 400 Wh/mi, which is not great. That means to go 20 miles, you use about 5 kWh of energy or about $0.40.
You can factor in the % of the $15.05 base charge as you wish. I remove it since other things in my house require a connection to the grid.
Tires and insurance are assumed to be the same with every car.
No oil changes anymore which is a benefit.

 

[GtiMart]

TeslaFi will not eliminate vampire drain. When configured properly, it will not ADD any vampire drain by keeping the car awake. Using TeslaFi will give a slightly better picture of power consumption than looking at the cards in the UI because it also tries to count power used when not driving. Better yet, don't look at any consumption, look at the charging records. IT should give a reasonably good picture of input power, before losses. The most precise would be to have a counter on your power panel directly.

 

[Pstreicher1]

Thank you all for replying. I like the idea of that power/amp meter to record each charging session.
At least with that I can create a paper or google sheets log if nothing else and maybe be able to figure what it is costing
me each month for charging. People are always asking me how much to charge the car so i want to have some ammunition.
I think I have looked at the Teslafi app once before but will look again.

 

[Rhinodad]

Newbie here. Got my 2021 Model X on December 10th, 2020. No problems found luckily and having a ball driving now. I am finding a new way to drive thanks to the electric motors making things quick. Not to mention the nice road handling and so much else.

So, after many charges now, about every two days using the Wall Connector at 47 amps and 240 volts.Tonight I decided there must be a way to put some formulas into a spreadsheet to figure out how much it is costing me to charge.

Tampa Electric or TECO as it's called (a Duke Energy company) charges the below amounts as of my 12/09/2020 billing.

Base charge of $15.05 / kWh

Energy charge of $0.05375 / kWh
Fuel charge of $0.02285 / kWh

Total of the last two is $0.0802/kWh.

Using P=I*E
P=? (kWh)
I=47
E=240
(Not at all sure about the above)

Now how do I complete and or correct this formula to get my total cost to charge
the 165 miles needed to get to the top charge of 334 miles as shown after each full charge?
I haven't used electrical formulas in a long time and I am so confused by it now.
Can anyone shed some light on this for me and maybe other members here?

Thanks in advance,
Paul in Tampa

Check out Optiwatt - it will track your charging and costs

 

[juliusa]

About 1 kWh for every 3 miles driven. Just take your monthly bill and calculate the cost per kWh. I would use the "above 1000 kWh" rate assuming you were using 1000 kWh before you got the Tesla. Looks like about $.11 per kWh.

Divide the miles driven by 3 and multiply by the $.11 per kWh. If you drive 1200 miles that were charged at your home, that would be 400 kWh of charging. $44.

Another way to look at the same calculation is you drive 3 miles for $.11 - so about $.037 per mile.

 

[Pstreicher1]

Sagebrush, I'm still trying to wrap my head around all of this.
I regularly see the charging rate at around 38-39 miles per hour with the 240v and 47a wall connection.
So, to figure this I divide the 165 miles needed to full charge by let's just say 38, which gives .42, rounded off.
That's 4 hours 20 minutes, which I believe is what the display settled down at after a bit before I walked away.
Using your formula above I would then calculate 4.2 * .24 = 18.8 kwh total kw used. Correct?
Then using my power company charge of $.0802*18.8 = $1.44 to complete the charge of 165 miles.
That doesn't seem right looking at that amount but if correct, wow!

 

[juliusa]

You calculations are little off.

4 hours 20 minutes is 4.33 hours.
240v x 47a is 11.28 kW

4.33 hours x 11.2 kW is 48.88 kWh

48.88 kWh x $.0802 is $3.92

My simplified method:
165 / 3 * .0802 is $4.41

I think if you took actual measurements my simplified method would be closer. The reported "38-39 mph charging" is based on rated miles and does not take into account phantom drain or driving conditions where you get less than rated range. If you read the forums, you will see most people seem to get less than rated range.

 

[SageBrush]

Sagebrush, I'm still trying to wrap my head around all of this.
I regularly see the charging rate at around 38-39 miles per hour with the 240v and 47a wall connection.
So, to figure this I divide the 165 miles needed to full charge by let's just say 38, which gives .42, rounded off.
That's 4 hours 20 minutes, which I believe is what the display settled down at after a bit before I walked away.
Using your formula above I would then calculate 4.2 * .24 = 18.8 kwh total kw used. Correct?
Then using my power company charge of $.0802*18.8 = $1.44 to complete the charge of 165 miles.
That doesn't seem right looking at that amount but if correct, wow!

240v * 47amps = 11,280 watts = 11.28 kW
Since Energy = kW * hours,
4 hours at that rate = 11.28*4 = 45.12 kWh

---
May I suggest a simpler approach ?
Look at the energy data card, located in the bottom left corner of the display
Scroll down to a card that has not been reset, so it represents your lifetime consumption

Read:
Lifetime miles
Lifetime Wh/mile. (Wh/1000)/mile = kWh/mile
The product of your lifetime Wh/mile and your utility rate in cost per kWh is cost per mile

Example: Cost per mile
Say lifetime Wh/mile is 240. That is 0.24 kWh/mile
If your utility cost is 10 cents per kWh then 10*0.24 = 2.4 cents per mile

 

[juliusa]

Example: Cost per mile
Say lifetime Wh/mile is 240. That is 0.24 kWh/mile
If your utility cost is 10 cents per kWh then 10*0.24 = 2.4 cents per mile

Simple is good! I think people usually apply some factor to that to account for charging inefficiency, and energy usage when the car is off which I don't think is captured in the lifetime Wh/mile.

 

[Nodrog D]

Why don't Tesla give us a useful Cost Per Mile calculator in the app and put us all out of our misery instead of all the useless games and things they keep sending us

 

[Pstreicher1]

Having taken in consideration all the above, I did another calculation and came up with the $3.92 approximation.
I then calculated what the same mileage would have cost me in gas for my old '99 Nissan Pathfinder which got 16.5 miles per gallon.
Using my local current gasoline costs at the pump I figured that I am saving around $10 every 100 miles now with a Tesla.

Now to get a couple more electric bills to compare to the year before to see what I can glean from that.

My current bill shows a considerable increase from last year's bill, which I expected. I have not done any calculation to see how much more it has cost from last year's bill. I am really not all that concerned but being a nerdy type I fuss over numbers and details and costs. Feeling the warmth of that cable the first time charging and seeing the 48a charging current on the dash, I knew it was going to add up each month. I also need the information to answer people who will always ask how much is it costing me to keep the Tesla charged.

 

[Pstreicher1]

While visiting my older brother in Clearwater the other night we got some Chic-Fil-A and next door was a WaWa store. Ron was telling me to pull in at the WaWa and have a look at the new Tesla charging stations. I think there were ten of them. It was my first time using a Supercharger and while we ate in the car and talked the battery pack was fully charged in 30 minutes and zero cost per the energy screen.

Question: I have read that when using a supercharger you are charged through your Tesla app. Is that correct and if so, how does that work? I see nowhere to input and apply a credit card. Does Tesla use my checking account from where they got my check for the car's down payment? I am also wondering if WaWa is in some type of promotional period with Tesla to offer this free charging to get more customers into the store. Although the several cars that were pulling into and out of these chargers, no one was leaving their car to go into the store.