Efficiency comparison Normal vs HV mode

I have been keeping detailed stats since I purchased the car in Dec 2017. I had an '15 Accord I was leasing that I was using on trips and just used the Clarity around town until I turned in the Accord in Mar 2018. Now that I've been taking the Clarity on trips and actually using the gas engine now, I felt it was time to do a comparison between driving the vehicle in Normal mode (i.e. using up the battery and then auto HV) vs strategic use of HV mode (using only on sustained highway drives that are beyond my electric range).

So far my results indicate that it is more efficient to strategically use HV mode vs driving the car in Normal mode.

In April 2018, I went on 2 trips the first half of the month and just let the car select the propulsion (Normal mode). During the second half of the month I went on another 2 trips that were to different places but the mileage and driving conditions were nearly identical and good enough to do a comparison. This time I strategically used HV mode on the highway.

From the picture, for the first half of the month, the vehicle attained a 57.9 mpg-e rating using Normal mode. For the second half of the month, the vehicle attained a 56.4 mpg-e rating strategically using HV mode. Yes this is lower, but to compare apples to apples we have to mix the same amount of EV driving to the second half of the month that I did during the first half. Once you hypothetically equalize the EV driving (i.e. same amount of Electricity used) to make an apples to apples comparison, the vehicle attains a 63.7 mpg-e rating. So far, the stats support using the propulsion sources advantageously.

 

By the way, my overall cost per mile, the best "where the rubber meets the road" figure to compare against a gasoline car is $0.045 per mile. The Accord hybrid was $0.057 per mile.

 

Fair enough. I will continue to post my results in the coming months.

 

Tangible, sure no problem. What I mean by strategic is basically this:

1) Determine whether your trip is going to take you beyond your current available electric range.
2) If answer to 1 is yes, then push the HV button when you get on the highway.
3) If/when you encounter slower, stop and go driving thru towns/cities, push the HV button again and go back to EV mode.
4) Push HV button again when you are back to sustained highway speeds.
5) Repeat 3 and 4 until you have determined that your current available electric range is sufficient to get you to a place to charge.
6) If you are within the available electric range to get to your charging location (home, for example), turn off HV and finish the drive in EV mode.

I would only use HV charge if you don't have enough charge in the battery to take advantage of step 3.

 

I'm not sure there is one Demian. Electric is more efficient than gas any way you slice it. In Mar 2018 when I drove nearly 100% EV, including some highway speeds around town within my electric range, my cost per mile dropped down to $0.036 from my overall average of $0.045. I can still get 100 mpg-e at highway speeds around town.

Sounds like an experiment you could conduct and report the result.

 

That's the great thing about this car dstrauss, it gives you the options. You could just get in this car and drive, no button pushes required, for convenience. Or you can strategically use the gas and electric power sources to maximize efficiency and comfort. Best car I've owned.

 

Using the navigation system certainly helps with that HV -> EV switch over on the last leg, but as @Kendalf pointed out, it's probably best to give yourself a little mileage buffer before the switch is made. For me, it's mostly highway driving to home, including a short stint at turnpike speeds (75+mph) before I get there.

Electricity is more efficient in any driving, the issue with our cars is the energy storage. Since it takes more energy to drive at sustained high speeds (I have had the same observation as @Kendalf on the 65 mph threshold), and the bulk of this energy is in the gas tank, not the battery (7 gal of gas x 32.78 kWh/gal) vs (14.3 usable kWh in battery), it makes sense that in these situations the gas tank should be used. This is also where the gas engine is most efficient. Better to save that limited electric energy to capitalize on the vehicle's supreme efficiency in the slower/stop and go town/city driving.

 

@Demian Johnston do you have a level 2 charger at home? If so, do your 20 mile round trip then charge it and log the kWh to recharge it back to full. Then, on your second round trip, use HV mode instead. After you get back, charge it up (shouldn't be much at all since you used HV mode), and fill the gas tank up and report the gallons used. Convert the kWh used to gasoline gallons (32.78 kWh/gal of E10), and then compute your mpg-e for both trips and compare. My guess is that EV would win in efficiency. The second part of the calculation (and the real truth of the matter) is the cost. Attain your cost per kWh from your electric bill (mine is $0.119/kWh), and the cost to fill up the gas tank. Then compare costs. If you can do this experiment, report the result to us. Thanks.

 

You can do a rough calculation using the HondaLink app. You have to make note of the % charge in the Battery tile when you first start charging. Then multiply the % difference by 17 kWh to approximate the amount of kWh used on your 20 mile round trip.