# Forums

## Is there an easy way to calculate how much it costs to charge?

I just had someone ask me what it costs to charge up and use the S...
I figured it a couple of ways on a napkin, but think I may be having conversion difficulties. I searched using Volkerize, but now my head's spinning...

I was looking at the following, from my car:

I've driven 2400 miles, using 770kWh
If I figure that our cost per KW is \$0.39 (thank you LIPA)
770 * (how many hours did it take???) *.39 = ???

Bleh... Tutor?

Kleist | July 23, 2013

The cost of electricity is kWh... so you don't need to know how long the charging took.
Rule of thumb : energy used times 1.25 is energy charged.

770 * 1.25 * 0.39 = \$375.38

Sudre_ | July 23, 2013

For your back of the napkin method that's it.
770kWh * \$.39 per kWh=\$300.30 your done.

There are charging inefficiencies that are left out in that calculation.

2400 miles with a similar car in class which get at best 18mpg is about 133 gallons of gas. The last gas station I passed and payed attention to in STL was at 3.77... so you would have spent \$502 in gas.

stsanford | July 23, 2013

Thanks all. So, for us in NY (Specifically on Long Island), there isn't a huge savings it would seem... Now if our rate was lower, then it might make a difference. May need to switch plan to a TOC plan.

Thanks again!

soma | July 23, 2013

um, there is a calculator on the Tesla site exactly for doing this:

http://www.teslamotors.com/charging#/calculator

pgiralt | July 23, 2013

How are you getting the 0.39? That seems extremely high so I looked it up and found this:

http://www.lipower.org/pdfs/account/rates_resi.pdf

Looks like there is a daily charge of \$0.36 and then the energy rates are all below \$0.10 per kwh. That will make the cost of the electricity for those miles less than \$100.

dortor | July 23, 2013

also if gas goes up in price you may be better than you think - but yeah if kWh prices are above \$.30/kwh and gas is less than \$4.00/gallon then EV cars aren't as good as they could be - long term trends however favor the EV…

bigbit | July 23, 2013

Jeez
Here (NL) it the cost of a lt gas are 1,70 euro and 1KWh is 0,23€
Hmmm let me refrase that 1,7*3,785=6,43 euro*1,32=8,50\$ per gallon and electricity is about 0,33\$
So 2400/18*8,50=1133,33\$
And Tesla 770*1,25*0,33=317,62\$

I must be dreaming, that wouls be 800\$ difference every 2400 miles so...
I just got happier i ordered....

bigbit | July 23, 2013
Tesla-David | July 23, 2013

We are lucky in Washington State as our power comes predominately from Hydopower, with low rates (\$0.08/kwh). Something EV owners should consider is putting solar panels on your homes. I am a net producer of electricity, and my 13.2 kwh solar array (55 panels) produces enough electricity for our all electric home and Tesla charging. Washington State has incentives which make purchasing solar panels/inverters made in Washington State very attractive. I sell every kwh I produce back to the grid for \$0.54/kwh and buy back what I need at \$0.08 kwh. I pay no electric bill and our electric utility writes a check for up to \$5,000/year to reimburse us for power generated over the year. Therefore, my Tesla charging is free at home as we generate everything we need for home and car. I am sure other states have incentives in place to encourage homeowners to consider solar. Other options by SolarCity are currently not available her in WA, but are in many states and are worth looking into.

Xerogas | July 23, 2013

At \$0.12 per kWh (after midnight, EV-TOU2 rate from SDG&E), my total electricity cost is \$2.75 for 60 miles of travel each day. That includes vampire losses, charging inefficiency, etc., because I'm reading the energy usage from my house meter.

So if you figure out how much 60 miles worth of gasoline costs you in your particular car, then you can compare the two. In my case, I was driving a Honda Insight @52mpg, so my gasoline costs for the same 60 mile commute were \$4.61 (assuming \$4.00/gallon). My Honda Accord (at 25mpg) was costing \$9.60 for the same commute.

\$2.75 < \$4.61 << \$9.60

cfarndt | July 23, 2013

LIPA rates should not be more than \$0.16-\$0.20 kWh. I was just checking my LIPA bill.

KennyB@US-FL | July 23, 2013

Basically all I do is take total \$\$ on the bill and divide the kwh used for the month. With all the city, state and federal taxes it works out to about \$.113/kwh.

RZippel | July 24, 2013

In Germany, especially the federal state of "Hessen", that is easy to answer, there is a network of free Type2 32A/3 phase chargers from Mainova, a regional energy supplier, rated at 22kW. If you only use them, the Tesla "fuel" is free (for now).

Zelaza | July 24, 2013

Tesla-David writes: " I sell every kwh I produce back to the grid for \$0.54/kwh and buy back what I need at \$0.08 kwh. "

This says that for every kwh you put into your Model S you don't earn \$0.54. At about 3 miles/kwh, you lose \$0.18 for every mile you drive your EV. Using Kleist's correction factor (mentioned earlier in this thread) of 1.25 to account for charging losses, the electrical power loss is \$0.225 per mile. An ICE @ 20mpg and gas costing \$4.00 per gallon costs \$0.20 per mile. Your EV is not saving you very much money.

Docrob | July 24, 2013

Zelaza, your logic only holds if David is charging his car at home during the day, otherwise he still exports all that power for 0.54/Kwh and then charges his car on 8c/Kwh power overnight. This is one of the nexpected benefits of feed in tariffs, not only do they encourage production. During daytime peak demand but they also encourage shifting consumption to off peak hours to maximise the feed in therefore reducing daytime peak demand even further.

SamO | July 24, 2013

@Zelaza,

Wrong. You are selling when it's expensive, and buying when it's cheap.

herkimer | July 24, 2013

I checked my electrical bill, and here is how it stacks up for me. I don't have LIPA and my rates are somewhat lower but here it is:

Total miles on Model S: 4120
Total kWh used: 1205
Cost of Electricity: .18 per day (base charge) + .08613/kWh

1205 * 1.25 = 1506.25 kWh
1506.25 * .08613 = \$129.73

I have had the car for 60 days, so even if you include base charge of .18 per day for only the car (applies to all electricity for household), that would add \$10.80.

So grand total cost of energy for my Model S over two months and 4000+ miles, comes to \$140.53.

4000 miles with a gas car that got 40 mpg would use around 100 gallons of gas. Gas here costs about 3.60 per gallon. So simple guestimation is that the same miles would have cost me at least
\$360 in a fuel efficient gas car.

360 - 140 = \$220 That's how much I have saved on gas so far.

I would also have had to pay for a 3000 mile oil change on a gas car, so add that at 39.00 (since no oil change needed for Model S) and the Model S savings so far goes to \$259. And this is just the beginning!

Add to all this the sheer joy of driving the Model S and starting with a "full tank" every morning, there is simply no contest!

olanmills | July 25, 2013

\$0.39/kWh? Dang. My cost is more like \$0.085/kWh.

Gas_Passer | July 25, 2013

The DOE has come up with another way to calculate the electric costs of driving an EV: the eGallon. You plug in the state you live in, and it takes the average electrical price for the state and the average kWh/mile efficiency of the top 5 EVs in the US (which includes the MS), and it spits out the price/"gallon" of electricity. The current US average is \$1.18/gallon for EVs. Totally different way of looking at it (with lots of assumptions that may or may not be accurate for MS owners), but one that average ICE drivers can understand.

http://energy.gov/articles/egallon-how-much-cheaper-it-drive-electricity

LionPowered | July 25, 2013

Looks like Hawaii is the least advantageous with gas and egallons being almost equal in cost. They need geothermal or some other way to make electricity!

KWTESLA | July 25, 2013

stsanford

My S average is 321 watts/mile that = .321 X your cost / Kilowatt .12 = .03852 per mile.
Take your average cost/mile and multiply it times number of miles to recharge.

.03852x 180 miles =\$6.93

Some of you pay extremely high electrical rates I have been reading your post at .32 .36 and .39 per KWH. The whole sale price for Electricity hovers around \$32.00/Mega Watt. That puts the wholesale cost at .032/ KW. Someone is making money when you charge your car ! Still far less than gas.

Speed Racer | July 25, 2013

LIPA as of July 2013 charges 8 cents for delivery charge and another 8 cents for power for a total of 16 cents per KWH that is only for the first 250 kwh... after 250 kwh it goes to 9 cents for power (and remains at 8 cents for delivery) so it total 17 cents per KWH... so cut your number by more then half ...

jamesd567 | July 25, 2013

In San Diego, SRE will provide EV owners \$0.15 per kwh pursuant to a TOU (time of use) plan.

I installed solar in 2009. 2.4kw nameplate capacity for \$11K net.
Over the life of the array it should work out close to \$0.10 per kilowatt hour. Since i was paying \$0.18/kwh, its a great deal.

Today, Solar arrays are about 1.30 as efficient and lower cost to install. By the time the extra credits expire ( i hope not, but lets see) solar will still make great sense so when I buy more panels at the same time as I buy a Tesla, then I would estimate its going to cost me about \$6 to "fill up" and at \$5 a gallon average over the life of the car (its \$4.34 here), then at 250 miles, it all works out to 172 mpg.

However, that's only going to get better. 1000 mpg is over the horizon folks, as solar efficiencies and gas prices climb and battery efficiencies rise and battery costs decline.

As gasoline usage declines, gas stations will close. Refineries may close, but I suspect they'll just export more (thats already happening).

Gasoline prices have always risen somewhat faster than fuel economy has (at least since 1970). I'd expect there will be even more upward pressure on gasoline prices, as oil companies try to maintain or improve profits in the face of declining volumes. the oil companies certainly have no problem screwing the consumer for as long as they can.

ramtaz | July 25, 2013

I have 2200 miles in 47 days on my new Model S.
AT a cost of \$434 for gas vs \$63 in electricity, you can understand why my luxury ICE sits in the garage.

Devin B | July 25, 2013

We get \$0.05/kWh from 12-7, been charging my leaf for 2 years at \$10-\$20/month vs my \$220-\$240/month gas bill. Went solar last fall and our electric bills have been negative only offsetting 60% of our usage because we sell back at \$0.35/kWh during the day and charge at \$0.05/kWh at night.

End of the month are net usage is 200-300 kWh, but they owe us \$

:)

Can't wait to get my S next month! Already sold the leaf and waiting......