Mike's wife's monthly Kona EV efficiency report

[JoeS]

@navguy12, appreciate you having the perseverance to publish this every month and that you are doing wall-to-wheels (which is what the US EPA uses) instead of the car's battery-to-wheels display. Twelve years ago I tried the same with my Mitsubishi i-MiEV for 8000miles but eventually gave up as running the heater or aircon would dramatically alter the numbers for that car and there was no way of separating the motive power consumption (which is what I was interested in) from everything else.

Playing with numbers...
Given that your Kona gets 19.36kWh/100km (wall to wheels),
and 1USMile = 1.609km
Thus this yields 311.5Wh/mi (wall-to-wheels)
I am particularly interested in the fuel costs, especially as that is the metric I use to compare with my ICE-driving friends.
CAD$1.44= US$1.00
Using your fuel costs,
CAD$0.0392/km = US.02722/km = US$0.03572/mile = US3.57¢/mile

This is ridiculously inexpensive electricity compared to our costs nowadays here in California, where the going rate is on the order of US$0.60/kWh and which is about what the commercial stations are charging to charge.

@navguy12, using your consumption number of 19.36kWh/100km = 311.5Wh/mi , this means that our costs are US18.7¢/mile, or more than 5X as expensive as yours and about on par with a comparable ICE vehicle, especially considering California's gasoline costs which are very high. I'll stop here, depressed. :-(

OTOH and happily, I have fully-amortized solar PV large enough to be a net annual producer, so my electricity at home is almost 'free'.

Even though I just did a pleasant 500-mile Kona trip to visit family after Christmas (and to gently break in a brand-new motor+GRU replaced under warranty and about to change the oil and put in a Vortex plug), I'll be sticking with my 2013 TMS85 and its free Supercharging for long trips.

... or maybe I made a misteak in the above calculations...

 

[navguy12]

Glad someone else is as obsessed with these things as I am

@navguy12, using your consumption number of 19.36kWh/100km = 311.5Wh/mi

Using your fuel costs,
CAD$0.0392/km

Just to keep apples to apples, the 19.36 kWh/100 km figure is only applicable to the 31 days of Dec 2024 whilst the fuel cost is the average over the whole 4.42 years of ownership.

Looking at the 4.42 year summary page in closer detail:



...the average kWh/100 kms is actually only 16.956.

CAD$1.44= US$1.00

I do caution when using a direct conversion like this as it excludes things like purchasing power parity and the like.

Also, of course, the street rate that one would actually get for a single US dollar when exchanging for Canadian dollars is somewhat less than the "official rate" that is reserved for bank to bank transactions.

Using what my wife actually paid, per kWh, in Dec 2024 (47.7 cents CAD) may also lend some more context to the point you raise.

With a going rate of 60 cents US per kWh in California, if I were to exchange that US figure for CAD at my local bank, it would yield perhaps 84 cents which is not quite double our price, but the point is taken.

... or maybe I made a misteak in the above calculations...

No, it looks like your math is sound.

I'll be sticking with my 2013 TMS85 and its free Supercharging for long trips.

I know that when I travel very long distances and only use superchargers, the energy cost math works out to what it cost me to drive a new Prius, assuming the Prius gets the claimed EPA highway efficiency...whereas I have been known to cruise for hours on end well above EPA highway test speeds

FWIW, I also keep track of my 6.59 year old TM3, in the same manner, here:

https://www.teslaownersonline.com/posts/423903/

 

[JoeS]

CORRECTION and UPDATE
@navguy12, thanks for setting me straight and for the link to the Canadian Tesla forum.

I see that for your overall average consumption, instead of being 19.36kWh/100km, I should have used 16.956kWh/100km

I also see that your average electricity cost has been CAD$0.231/kWh (= US$0.1604/kWh) which is still about 1/4 of what it is here in California.

Here are my revised numbers -
16.956kWh/100km = 272.82Wh/mi
Using US$0.60/kWh results in a fuel cost of US$0.1637/mile = US16.4¢/mile

Comparing this to a small US SUV which gets 25mpg and a present California gasoline cost of US$4.50/gallon yields US$0.18/mile.

Concluding that, sadly, we can no longer (in California) claim that our fuel costs are significantly less than comparably-sized gasoline vehicles. :-(

Happy New Year!

 

[navguy12]

CORRECTION and UPDATE
@navguy12, thanks for setting me straight and for the link to the Canadian Tesla forum.

I see that for your overall average consumption, instead of being 19.36kWh/100km, I should have used 16.956kWh/100km

I also see that your average electricity cost has been CAD$0.231/kWh (= US$0.1604/kWh) which is still about 1/4 of what it is here in California.

Here are my revised numbers -
16.956kWh/100km = 272.82Wh/mi
Using US$0.60/kWh results in a fuel cost of US$0.1637/mile = US16.4¢/mile

Comparing this to a small US SUV which gets 25mpg and a present California gasoline cost of US$4.50/gallon yields US$0.18/mile.

Concluding that, sadly, we can no longer (in California) claim that our fuel costs are significantly less than comparably-sized gasoline vehicles. :-(

Happy New Year!

Yea, it sucks when the true operating costs of ICE vehicles are still externalized onto & subsidized by everyone.

 

[navguy12]

Results for Jan 2025:







Operating costs this month:



Summary of costs as of 31 Jan 2025:



Total operating costs, per km (total costs minus capex costs):

$2.8928 - $2.5096 = $0.3832/km

 

[navguy12]

Results for Feb 2025:






Operating costs this month:


Summary of costs as of 28 Feb 2025:



Total operating costs, per km (total costs minus capex costs):

$2.8530 - $2.4736 = $0.3794/km

 

[navguy12]

Results for Mar 2025:







Operating costs this month:



Summary of costs as of 31 Mar 2025:



Total operating costs, per km (total costs minus capex costs):

$2.8064 - $2.4309 = $0.3755/km

 

[navguy12]

Results for Apr 2025:







Operating costs for month ending 30 Apr 2025:


Summary of costs as of 30 Apr 2025:



Total operating costs, per km (total costs minus capex costs):

$2.7478 - $2.3795 = $0.3683/km

 

[navguy12]

Results for May 2025:







NOTE: actual trip odometer for this month is 317.1; it had not been reset at the end of last month.

Operating costs for month ending 31 May 2025:



Total operating costs, per km (total costs minus capex costs):

$2.7109 - $2.3470 = $0.3639/km

 

[navguy12]

Results for June 2025:







Operating costs for month ending 30 Jun 2025:



Summary as of 30 Jun 2025:


Total operating costs, per km (total costs minus capex costs):

$2.6982 - $2.3354 = $0.3628/km

 

[navguy12]

Results for Jul 2025:







Operating costs for month ending 31 Jul 2025:



Discussion: this is the second time we had to replace the button cell battery in my wife's key FOB in the past ~six months.

Summary as of 31 Jul 2025:



Total operating costs, per km (total costs minus capex costs):

$2.6764 - $2.3099 = $0.3665/km

 

[BobNY13]

Thanks for posting all this. I just started keeping track of similar data for my 2025 Kona EV and see so far 86% charging efficiency (car's record of kWh used/wall record of kWh made up) which agrees well with your 84.4%...so mine isn't far off.

 

[navguy12]

Results for Aug 2025:







Operating costs for month ending 31 Aug 2025:



Summary as of 31 Aug 2025:



Total operating costs, per km (total costs minus capex costs):

$2.6949 - $2.3015 = $0.3934/km

 

[BobNY13]

@navguy12 , when you look at the difference between the car's reported kWh and the actual charging kWh for individual charging sessions, do you note a relationship between the loss/efficiency and the charge set point? (sorry if you've commented before, the search function was not helpful)

I only have a few months of data, but on my normal charges to 80% SoC, the charging efficiency (car-reported usage / actual kWh input) ranges from 86-90% while on the three times I charged to 100%, the efficiency ranged from 80-84%.

 

[navguy12]

@navguy12 , when you look at the difference between the car's reported kWh and the actual charging kWh for individual charging sessions, do you note a relationship between the loss/efficiency and the charge set point? (sorry if you've commented before, the search function was not helpful)

I only have a few months of data, but on my normal charges to 80% SoC, the charging efficiency (car-reported usage / actual kWh input) ranges from 86-90% while on the three times I charged to 100%, the efficiency ranged from 80-84%.

I lost access to the ability to parse that type of data back in July 2022 when we moved from our house (with private garage with individual hydro feed with specific metering of the specific car charging circuit(s)).

If you go to the very first post of this thread, and click and enlarge some of the small embedded attachments, you will see this type of stuff:







The above data (illustrated examples of what I am trying to explain) shows how I was able to separately monitor the circuit feeding the charger that my wife’s Kona was plugged into.

In the first of the three above screenshots is the typical shot from the dashboard, where a simple multiplication of the Wh/km and the km travelled comes to (923 km X .118 Wh/km) = 108.91 kWh.

The next two shots are inline sensors (the middle shot a stand alone inline sensor and the bottom shot a separate, more sophisticated inline sensor (that wasn’t online for the whole month being measured, thus the red handwritten information with some added kWh) that essentially show ~128 kWh actually consumed by the circuit for that month.

In this example 108.91/128 = ~85% charging efficiency.

The month before we moved, June 2022, the amalgamation of the previous 34 months of this type of data showed as:

do you note a relationship between the loss/efficiency and the charge set point?

Unfortunately, our charging characteristics were/are always the same…charge to 90% and then drive it (usually for a few weeks) until it needs charging…so I cannot tell you if the charge set point has any effect on overall charging efficiency.

However, anecdotally, if the month of data included a “long” trip (such as a trip to the inlaws and back for an aggregate of ~500 km in two days), the charging efficiency numbers were always better than the global average.

 

[navguy12]

Results for Sep 2025:







Operating costs for month ending 30 Sep 2025:



Summary as of 30 Sep 2025:



Total operating costs, per km (total costs minus capex costs):

$2.6784 - $2.2869 = $0.3915/km