How would i calculate how much it cost me to charge?

[jlucero]

pardon my extreme ignorance, ive been driving my Tesla 70D Model S since 2015, but not proficient at anything electrical.

i charge my car at night in my condo, and my wife gave me an assignment to figure out how much we spend on charging this vehicle. so here are the facts, but not sure how to calculate it. any help would be great.

so lets say im at 50 mile range left. my max range is 240, but lets say i limit it to 200. so i need 150 miles of charge. in my condo, i have a Nema 14-50 i believe, looks like this.

https://www.amazon.com/Leviton-279-...locphy=200524&hvtargid=pla-357917644205&psc=1

i believe it is 240V, 50A, but not 100% sure. i dial it down on my car to charge at 20A. usually i think i get around 25 miles per hour charged on this. so that would make charging time around 6 hours.

with Edison Power, i looked up my rates, and i believe it is 10 cents per kWh after 10pm, which is when i schedule the car to charge. does this mean that im paying 10 cents times 6 hours, or 60 cents? or does Amps matter? not sure what other variables are involved.

thanks.

 

[ran349]

pardon my extreme ignorance, ive been driving my Tesla 70D Model S since 2015, but not proficient at anything electrical.

i charge my car at night in my condo, and my wife gave me an assignment to figure out how much we spend on charging this vehicle. so here are the facts, but not sure how to calculate it. any help would be great.

so lets say im at 50 mile range left. my max range is 240, but lets say i limit it to 200. so i need 150 miles of charge. in my condo, i have a Nema 14-50 i believe, looks like this.

https://www.amazon.com/Leviton-279-...locphy=200524&hvtargid=pla-357917644205&psc=1

i believe it is 240V, 50A, but not 100% sure. i dial it down on my car to charge at 20A. usually i think i get around 25 miles per hour charged on this. so that would make charging time around 6 hours.

with Edison Power, i looked up my rates, and i believe it is 10 cents per kWh after 10pm, which is when i schedule the car to charge. does this mean that im paying 10 cents times 6 hours, or 60 cents? or does Amps matter? not sure what other variables are involved.

thanks.

You are calculating incorrectly. I have the same car as you so I can tell you approximately how much it costs you based on your Edison rate of 10 cents per kWh.
It takes about .32 kWh to charge one rated mile. So if you have to charge back 150 rated miles, as per your example, then your cost at 10 cents per kWh would be:

(.32 kWh/rated mile) x (150 rated miles) x (10 cents/kWh) = 480 cents or $4.80 to charge 150 miles.

Or in other words, just multiply 3.2 cents times each rated mile added (based on 10 cents per kWh).

So, in your example, 3.2 x 150 rated miles = $4.80.

 

[Lasttoy]

Teslafi software gives me that with their SW. Along with every detail u will ever want about electrical facts.

 

[Watts_Up]

with Edison Power, i looked up my rates, and i believe it is 10 cents per kWh after 10pm, which is when i schedule the car to charge.
does this mean that im paying 10 cents times 6 hours, or 60 cents? or does Amps matter? not sure what other variables are involved.

If you have a Smart meter, your Electrical company might provides you with some consumption graph.
If so, you can check your hourly, daily, weekly... consumption.

I was travelling for one week and turned everything except my refrigerator.
So now I know my hourly refrigerator consumption, and I can deduct it to have a better idea of my night time car charging.

Teslafi software gives me that with their SW. Along with every detail u will ever want about electrical facts.

This give you the car consumption, but miss how much energy is really needed to charge the car.

 

[brkaus]

At $0.10 it costs you approx $0.48 per hour of charging at 20A.

(240v * 20a / 1000) * $0.10

edit to fix typo in price per kWh

 

[jlucero]

so does this mean if i charge 6 hours to get my 150miles at 20 amps, the calculation is this?

(240v*20a/1000)*.10*6 = $2.88

does ran349's calculation take into account my 20amps?

 

[ran349]

so does this mean if i charge 6 hours to get my 150miles at 20 amps, the calculation is this?

(240v*20a/1000)*.10*6 = $2.88

does ran349's calculation take into account my 20amps?

The formula is correct(assuming 240 volts is correct, but often it is slightly less than that), but it doesn't make sense that you only take 6 hours to charge 150 rated miles at 20 amps.

The reason I say that is because at 40 amps your charge rate would be about 29-30 miles/hour. Therefore, at 20 amps you would be charging at about 14-15 mph (not the 25 mph that you claim), since you would reduce your power by 50%, so in that case it should take you about 10 hours to charge 150 rated miles at 20 amps.

Is your car set to read rated miles or ideal miles? How many actual miles have you traveled when your car has used 150 rated miles? What is your lifetime Wh/mi driving efficiency?

I am asking because something doesn't add up right with your numbers so far.

 

[brkaus]

@jlucero The calculation that @ran349 presented is an approximation based on miles driven. The calculation I presented is how much the power coming out of the wall costs. Different approaches.

Yes, your $2.88 result is correct for 6 hours. But I don't know how many miles that gives you.

Also, if you have time of use with lower rates at night, make sure you aren't reducing the amps too much that charging is going into high rate period.

 

[Graffi]

After the charge is finished and before you unplug check the charging screen to see how many kWh you have added to your battery. Multiply this number by $0.10 for the cost. Keep a log book in your car to know how much each month costs.

Also just keep track of your miles, then multiply by the average cost per mile. If you average 333 Wh per mile, that is 3 miles per kWh, which in you case is $0.10 per kWh divided by 3 = $0.0333 per mile.

So, depending on Gas costs per gallon and electricity costs per kWh you can see that driving an EV is cheaper than Gas. At your electricity cost you can drive about 5 miles on electricity for every 1 mile with gas.