Calculating Charging Costs...

[Saibot]

I'm new to this and was wondering how to calculate charging costs. Looking on my electric bill, we pay:
1,000.000 kWh x $0.06329 (over 1,000.000 kWh x $0.07051).
How do I figure out cost per mile/kWh/etc?

I also downloaded Stats for Tesla and there is a place in the settings for my energy cost. I assume I just enter 0.06239? Is that correct? The local Supercharger is 0.31, so just wanted a sanity check since the cost is so much higher.

Thanks for the n00b help.

 

[powaking]

For me I only have 1 rate. As I also have delivery charges what I found easier for me to at least get an idea of how much it costs to drive per mile I just take my entire bill and divide by the number of kWh I used. That will give me a basis of per kWh I pay with all charges and taxes. I then take the wh/m my car is using and divide by 1000 to get how many miles I drive per kW (since I know how much I pay per kW). From there I take the miles driven per kW and divide by the amount I pay per kW and that at least gives me a basis of what I pay per mile. Right now its costing me about as much to drive per mile as it does our small commuter car a Kia Rio (which is averaging 30mpg based on Fuelly).

In your case you have different rates based on how much kW you use in the month so it might be tricky. I can't see why Tesla couldn't add a feature where you can input what your kW cost is and it can just show you what your cost or average cost is within the car display. Why do we still only have 2 Trip trackers?

 

[John Beans]

If you don't have a Tesla yet, the best way to calculate what the energy cost per mile (or km) will be is to take the average energy consumption of the car you want (in my case a Model 3 LR 19" at 253 Wh/mi or 152 Wh/km) and multiply that by your electrical rate.

But the exact model and how you drive (and even weather) affect this. I know my car is 253 Wh/mi because that's the lifetime average of mine over the 23000 miles I've had it.

My car: 0.253 kWh/mi x $0.1155 / kWh = $0.029 / mi
So my car, the way I drive it, at my electrical rates, in my weather over the last year, is 3 cents per mile.

If you want to estimate the energy needs of some theoretical average driver, go to Troy's Teslike chart and divide the green column by the size of the battery in the car to get Wh/mi (or Wh/km).

Teslike Range Table

 

[Squashplayer]

I use Stats for Tesla and it generates all kinds of cost-related numbers, including how much I am saving compared to buying gasoline. I think that looking at numbers is fun and informative and probably look at Stats every few days.

In the settings page, there is a spot to put in energy cost. You can also put in the current cost of gas and the gas mpg so that it can generate the comparison numbers. If you use a non-US based system (e.g liters/100 km), this app will allow you to switch to other measurements.

 

[ewoodrick]

Energy per mile times miles is amount of energy

A 3 can get 250 Wh per mile.
Energy is usually referenced in kWh, so 0.250 kWh/mi

1000 miles * 0.250 kWh/mi is 250 kWh

250 kWh times $0.6329 = your answer

 

[M3-Florida]

New M3 owner here - we also have split rates depending on monthly kWh usage. If I enter the higher tier rate (1000 kWh) then I will average the costs of both rates into my calculation. We also have other utility costs (delivery, access fee) so I will be doing as Powaking mentioned, and getting the TOTAL cost, not just the energy use cost, even though one could argue "you have to pay an access fee even without an electric car.

The last I read, supercharger costs are per state (Florida is .28/kWh) so they average the electricity cost among the utilities in the state) plus maintenance costs, etc.

It is more expensive for the convenience factor as well to keep people from using it as their daily charger if they can charge at home. Imagine if superchargers were the same price as house charging, the waiting in line would be crazy.

Just to note, superchargers are more efficient since they are DC high voltage. At home your car is converting AC to DC which has a loss. There is a 10-15% overhead on charging.

 

[VQTRVA]

For me I only have 1 rate. As I also have delivery charges what I found easier for me to at least get an idea of how much it costs to drive per mile I just take my entire bill and divide by the number of kWh I used. That will give me a basis of per kWh I pay with all charges and taxes. I then take the wh/m my car is using and divide by 1000 to get how many miles I drive per kW (since I know how much I pay per kW). From there I take the miles driven per kW and divide by the amount I pay per kW and that at least gives me a basis of what I pay per mile. Right now its costing me about as much to drive per mile as it does our small commuter car a Kia Rio (which is averaging 30mpg based on Fuelly).

In your case you have different rates based on how much kW you use in the month so it might be tricky. I can't see why Tesla couldn't add a feature where you can input what your kW cost is and it can just show you what your cost or average cost is within the car display. Why do we still only have 2 Trip trackers?

Just putting my actual numbers to your explanation:
1) Billed charge per kWh = Total Bill / kWh used = $115 / 745 = $0.12
2) Efficiency per kW = Wh/mi / 1000 = 250/1000 = 0.25
3) Cost per mile driven = 0.25/.12 = 2.08 <<< Not sure what this represent?

How I am calculating it - using 1000 miles driven in month:
1) Total Energy in Wh used for 1K miles = Number of miles driven * Model 3's Wh/miles (efficiency) = 1000 * 250Wh = 250000 Wh
2) Convert to kWh used = Take #1 / 1000 = 250 kWh
3) Total Electric Cost for month = kWh * cost per kW = 250 * $0.12 = $30
4) Cost per mile = #4 / #3 = $30/1000 = $0.03

vs. Gas on same 1000 miles:
1) Total Gallons used in month = Total Miles / Miles per Gallon = 1000/30 = 33.333 gallons
2) Total Cost of gas (gal) used for month = #1 * $2.56 per gallon = 33.33 * $2.56 = $85
3) Cost per mile = Total Gas cost for month / total miles for month = $85/1000 = $0.085

 

[powaking]

Just putting my actual numbers to your explanation:
1) Billed charge per kWh = Total Bill / kWh used = $115 / 745 = $0.12
2) Efficiency per kW = Wh/mi / 1000 = 250/1000 = 0.25
3) Cost per mile driven = 0.25/.12 = 2.08 <<< Not sure what this represent?

How I am calculating it - using 1000 miles driven in month:
1) Total Energy in Wh used for 1K miles = Number of miles driven * Model 3's Wh/miles (efficiency) = 1000 * 250Wh = 250000 Wh
2) Convert to kWh used = Take #1 / 1000 = 250 kWh
3) Total Electric Cost for month = kWh * cost per kW = 250 * $0.12 = $30
4) Cost per mile = #4 / #3 = $30/1000 = $0.03

vs. Gas on same 1000 miles:
1) Total Gallons used in month = Total Miles / Miles per Gallon = 1000/30 = 33.333 gallons
2) Total Cost of gas (gal) used for month = #1 * $2.56 per gallon = 33.33 * $2.56 = $85
3) Cost per mile = Total Gas cost for month / total miles for month = $85/1000 = $0.085

Had to highlight your message as it was in a totally different color and hard to read.

I may have worded it incorrectly but it goes as follows.

1000/250 = 4. This is the number of miles per 1000kW.
Your rate is $.12/kW so you take that and divide by the number of miles driven per kW. $0.12/4 = $0.03

 

[AlanSubie4Life]

I'm new to this and was wondering how to calculate charging costs. Looking on my electric bill, we pay:
1,000.000 kWh x $0.06329 (over 1,000.000 kWh x $0.07051).
How do I figure out cost per mile/kWh/etc?

I also downloaded Stats for Tesla and there is a place in the settings for my energy cost. I assume I just enter 0.06239? Is that correct? The local Supercharger is 0.31, so just wanted a sanity check since the cost is so much higher.

Thanks for the n00b help.

Mostly what others have said. Your rates are so low that the costs are going to be low. Make sure you include all the transmission and distribution fees. I thought usually in Oregon the total cost per kWh was closer to $0.10/kWh but maybe not.

Anyway, whenever you have that, just take your Wh/mi in the car, and in summer multiply by 1.2, and in winter multiply by 1.4.

So if you have 230Wh/mi on your lifetime in-car meter, your actual costs are probably about:

1.2*230Wh/mi*$0.10/kWh = $0.027/mi

This is assuming you drive about 10-15k/yr.

The 1.2 is to account for charging losses (12%) (and the vampire drain). The 1.4 number is to help account for preheating, etc that you may do in winter (the 1.4 factor may be calibrated to a colder winter environment than Oregon, so you might do better - depends on whether you garage your car, etc.). These are just rough approximations. The important thing is to not calculate costs directly based on the in-car meter - it needs to be scaled up. Less scaling is needed when using Superchargers, as they are inherently more efficient from plug to battery (direct DC). Obviously there are conversion losses built into the high Supercharger rate; they are not magic. (I have no idea how Tesla bills, but presumably only for the energy actually delivered to the battery, in which case it is effectively “100%” efficient.)

For the Stats app I think it does some of this scaling for you when calculating your costs, but I have not paid attention to it (EDIT: just checked, Stats appears to use a scale factor of 1.12 - which is about right for charging efficiency and aligns with the 1.2 number above (as it is scaling up the actual kWh added to the battery, and not using the in-car meter, so already includes vampire drain in the pre-scaled number - so a smaller scale factor can be used). I also cross checked with Chargepoint app and the calculated $ from Stats align pretty well with the Chargepoint numbers if I convert the Stats $ to kWh using my specified Stats rate. Can’t actually compare $ directly since the CP is free to me. You don’t want to use the Stats kWh numbers to compare because that is energy added to the battery, not the energy from the wall.
(For calculating costs all that matters is what you draw from the wall, not what is on the meter in the car or what is added to the battery.)

 

[VQTRVA]

Mostly what others have said. Your rates are so low that the costs are going to be low. Make sure you include all the transmission and distribution fees. I thought usually in Oregon the total cost per kWh was closer to $0.10/kWh but maybe not.

Anyway, whenever you have that, just take your Wh/mi in the car, and in summer multiply by 1.2, and in winter multiply by 1.4.

So if you have 230Wh/mi on your lifetime in-car meter, your actual costs are probably about:

1.2*230Wh/mi*$0.10/kWh = $0.027/mi

Isn't your math output = $27.6?

 

[AlanSubie4Life]

Isn't your math output = $27.6?

There is a kWh and a Wh. I guess I could add *1kWh/1000Wh to make it less confusing, but technically it is correct either way. I just did not explicitly do the unit conversion.

 

[VQTRVA]

There is a kWh and a Wh. I guess I could add *1kWh/1000Wh to make it less confusing, but technically it is correct either way. I just did not explicitly do the unit conversion.

Yeah for a noob like me to conversion rate, that was what was missing.

 

[BestHand]

To calculate exact cost it is not so eazy, as you have to take all things into account, not only rate , but also delivery charge and some surcharges. Some charges take into account KWH consumed and some of them not. But generally you can calculate roughly cost of 1 KWH just dividing your total bill amount on KWH consumed. Let say your bill was $65 and consumed 200 KWH. So, roughly you paid $0.35 for 1 KWH. So, now just multiply 0.35 on every KWH consumed by your Tesla.

 

[Pete_in_FL]

To calculate exact cost it is not so eazy, as you have to take all things into account, not only rate , but also delivery charge and some surcharges. Some charges take into account KWH consumed and some of them not. But generally you can calculate roughly cost of 1 KWH just dividing your total bill amount on KWH consumed. Let say your bill was $65 and consumed 200 KWH. So, roughly you paid $0.35 for 1 KWH. So, now just multiply 0.35 on every KWH consumed by your Tesla.

One could argue that fixed distribution costs and other misc. charges are something you have to pay whether or not you have a EV, so the true cost is the additional KW used by the vehicle times the rate when you charge.
Here in SoCal, changing to EV Time of Use rates will drop my summer KW rate from $.42 to $.13 if I charge outside the high rate periods. (Wife uses the AC a lot.)

 

[jerry33]

To calculate exact cost it is not so eazy, as you have to take all things into account, not only rate , but also delivery charge and some surcharges. Some charges take into account KWH consumed and some of them not. But generally you can calculate roughly cost of 1 KWH just dividing your total bill amount on KWH consumed. Let say your bill was $65 and consumed 200 KWH. So, roughly you paid $0.35 for 1 KWH. So, now just multiply 0.35 on every KWH consumed by your Tesla.

Correct. Electricity cost is the "current charges" on your bill divided by the kWh consumed. ($0.072 in my case). However, there is one more factor. The Tesla only records kW used during driving, so there is also the wall to battery losses (~15%) and time when the car is on but in Park. Some folks have put in a metre to measure the wall to battery losses. I just use $0.10 and call it a day.

 

[AlanSubie4Life]

One could argue that fixed distribution costs and other misc. charges are something you have to pay whether or not you have a EV, so the true cost is the additional KW used by the vehicle times the rate when you charge.

For me, these fixed costs are very small proportion of the bill though (sometimes zero), and the distribution and transmission costs (at least with SDG&E) are scaled according to your usage. It may be different for some locales of course; this is just for SDG&E.

For example, with my SDG&E bill, the only fixed charge is the minimum charge (which is a daily rate of 32.9 cents per day). If you exceed the minimum charge through use of electricity, however, it is not charged (they just want to make sure they extract at least ~$10 from you each month). All the other significant charges scale, so the cost of electricity use really is as simple as when you use the energy and how much (see a couple caveats below). SDG&E provides tariff summary tables with all the various charges totaled up so you don't have to think about it - it just tells you your cost per kWh.

The baseline adjustment credit here is a fixed rebate per kWh, due to my choice of tariff, TOU-DR-P. It just effectively reduces the cost per kWh to around 22 cent/kWh (exact rate depends on which time of day), assuming I don't go over 130% of my baseline allowance.

The biggest things I have to worry about are 1) whether obtaining a low nighttime rate significantly increases my daytime costs due to the rate for the chosen plan being more costly in the day than a competing plan and 2) (with my current plan) whether the EV usage becomes high enough that it pushes me over 130% of my baseline (which would make things extremely costly) - you can see for the winter bill if I had used more than 200kWh (175kWh to battery) more electricity (by charging my Tesla at home) that would have been an expensive problem - could have meant an effective rate of about 38 cents per kWh for some of that charging! I have some margin still though... I may switch to a different tariff in July, though right now I think what I have chosen is cheapest for me - the choice will depend on the status of free charging at work.

 

[Legen---dary]

My 3 gets about 150 Wh/km. Electricity, if I could plug-in at home, costs about $0.1 / kWh.

If I charge 50% over whatever state of charge I'm in, it works out to about 25 kWh of consumption.

25 kWh x $0.1 = $2.50

At the efficiency of 150 Wh/km, or said another way, 6.7 km / kWh that $2.50 should propel my vehicle 25 x 6.7 = 167 km

or said in terms of km/$, I get about 1 km per 1.5 cents. Not bad!!

Supercharging is different in my area. It gets billed by the minute depending on charging rate. Above 60 kW, 50 cents, below, 25 cents, so way more expensive for the privilege.

P.S. I wish the industry would switch to m/Wh as a measure of efficiency. It comes out to a nice human-intuitive number, and can be shortened in daily parlance to something like, "I get 6.7 m per Watt," dropping the hour, or better, when asked how efficient your car is, you could simply respond that it gets "6.7 m." It's also easy to translate to distance per kWh, like miles per gallon.

 

[Curb71]

I've been wondering pretty much the same thing but I didn't see anything here that answers my question. I have a SR+. Charge it to 90% each night. I have a 240v 30amp charger and it says I get 30 miles/hour. I pay .13 cents per kwh. How much does an hour of charging cost?

 

[Legen---dary]

I've been wondering pretty much the same thing but I didn't see anything here that answers my question. I have a SR+. Charge it to 90% each night. I have a 240v 30amp charger and it says I get 30 miles/hour. I pay .13 cents per kwh. How much does an hour of charging cost?

If charging at 7kW, then $0.91 per hour. Easier to round up to $1 an hour in your case.
I get about 45km of range per hour at that rate with the same car.
If you drive 60 miles (~100km) per day, it only costs a couple of dollars for you to recharge.
If you're driving 100km or less per day, I'd only bother charging to 70% rather than 90%.

Edit: people sometimes have a little trouble with kW vs kWh. I think an easy way to explain it is with speed and distance.
Speed is an instantaneous reading, like kW. Doing 10mph; using 10kW.
Distance is cumulative, like kWh. There's a time component allowing a sum of all those instantaneous speed/power readings. Think 10 miles took an hour. Like 10kW for an hour equals 10kWh.
Your power cost of $0.13/kWh just means you are measuring 1kW output for 1 hour. If you increase the power to 7kW for an hour it's just 7 x $0.13 per hour.

 

[Curb71]

If you're driving 100km or less per day, I'd only bother charging to 70% rather than 90%.

Thanks. Yes I did notice it said 7kW which is the only number I didn't understand where it came from. As far as the part I quoted from you, is that it's only for battery longevity or is there another reason?