Getting a handle on cost of home charging

[MtnMarty]

I've had my MY for a bit over 2 weeks now and am trying to figure out a method for determining the cost of home charging. I have a Tesla charger in my garage and by perusing my latest Duke Energy bill, I see I'm paying 13.6 cents/kwh including taxes/fees. (10 cents w/o). My one experience with superchargers on a quick trip to Charlotte cost 29cents. So is there an easy way to determine from the car computer what kWh I'm using in home charging ? It may be obvious, but not to me.

 

[ChrisMPK]

To get a rough idea you can take your miles driven x your average KWH/mile usage, divide by .92 for efficiency and multiply by $.136 to get dollars. This will tell you the total cost since new, which after a month or two should give you an idea of your cost per mile or cost per week, etc.

 

[GtiMart]

The car only reports consumption during drives, not total energy from the wall. You are missing cabin conditioning, energy used when you're sitting in the car in park, etc...
During charging you should be able to see the number of kWh added to the battery. IF you take that and add roughly 10% for charging losses you'll be close to what's pulled from the wall.
Applications like TeslaFi can maintain a registry of drives and charging sessions. They can tell roughly the wall power that was pulled, that would get you closer.
Otherwise you need to track power at the wall with some measuring device, or maybe your charger can?

 

[ChrisMPK]

I should have mentioned that you would have to subtract out any supercharging KWHs as well.

 

[ATPMSD]

So is there an easy way to determine from the car computer what kWh I'm using in home charging ?

From the car, no. But there are 3rd party apps that show how much your car took on a charge. You will need to account for power lost is the AC-DC transformer, which is roughly 5-10%. I do not use any of the 3rd party apps, but I am sure others do and will post what they use.

 

[GtiMart]

Yep. As said earlier I use TeslaFi. It will gather information about charging sessions and much more. You can set your own price per kwh and it will calculate charging costs for you.

 

[andaconda]

It can be straight forward. Look at the charging screen of the phone app just before you unplug the car. It will show there how many KWh that it added to the car. You can do the math from there. As an example from my last charge: 30KWh * .117 = 3.51 then 3.51 * 1.10 = 3.861 So taking in account for my 10% line loss - my total cost was $3.86 .

 

[GtiMart]

...but in that case, you should add 10% to that number to account for charging losses.

 

[MtnMarty]

To get a rough idea you can take your miles driven x your average KWH/mile usage, divide by .92 for efficiency and multiply by $.136 to get dollars. This will tell you the total cost since new, which after a month or two should give you an idea of your cost per mile or cost per week, etc.

so far this method seems just about right for me. What I really need is an approximation. TeslaFi seems a bit much and also is $50/year. Maybe I’ll do that later.

 

[rob1987]

Get Optiwatt app for your phone. It connects to your car and after you input the details of your electrical rate plan, it will calculate energy consumed, efficiently of charging and value both on-going and on a per charging session basis. It also does a calculation of gas savings, though I basically ignore those since it assumes 30mpg and premium gas prices, which don’t compare to what I used to get with my ICE.