When is switching to HV most efficient?

My commute is a lot farther than my range, so I run in HV when it's the coldest part of the day, which is also at the fastest speed. (67MPH) That seems to get the highest mileage overall.

 

Probably. But just make sure you use up the EV range before you get home to charge (or to work to charge if you can charge there). Otherwise, you'd be burning gas you wouldn't need to burn. Then again, with gas prices being so crazy low in much of the country, there might not be a very large difference in cost per mile between HV and EV.

 

Which efficiency are you trying to improve? Are you looking for more EV range or better mpg under the HV mode? If you just want overall efficiency improved, you can just drive and let the car take care of the switch. I have driven my 2017 PP for my commuting of ~40 miles. It was just a few miles longer than my EV range in summer, but almost 20 miles short in winter. I have driven my car with EV until it automatically switches to HV when the EV range runs out. This gave me better HV mode mpg, but the EV range is always limited and EV efficiency could not be increased much above 5-6miles/kWh. I changed my driving style and switched to HV mode in the middle of the commute to increase EV range and efficiency. Specifically, use HV mode on uphills and quick acceleration, but trying to keep the engine warm-up cycle to minimum. With this method, I improved EV efficiency well above 8miles/kWh, but the mpg is down. For me, electricity is more expensive than gas, so better EV efficiency with less mpg gives me better overall cost/mile.

 

Temp can make a HUGE difference, though I really wouldn't try to micromanage it. I may have been able to get higher overall mpg by micromnagement, but it really is more pain than it's worth when you figure out how much gas difference there is between 100MPG and 120MPG -- it's not very much!

 

I use HV for the hills I encounter and EV for the remaining sections, regardless of speed.

I have a 38 mile one way commute and I average 34 miles of EV each way utilizing the HV for hills approach.

Free charging at work helps with economics as well.

 

lochnersm in response to your OP and asked again post #7, in my opinion the answer is yes, EV can be more efficient at slower mph than at faster mph. ie if you can find a flat stretch of road with few stops. no traffic. for 50 miles and drive it at creep home speed the car will deliver nearly the max EV range. The numbers look something like this 8.9 Kw traction pack takes 6.6 +/- kw to charge and delivers approximately 5.5 kw where the wheels meet the road. So take 5.5 kw * 10 M/kw = 55 miles EV
I doubt anyone has ever achieved 55 mile true EV only range, I know I haven't, but in theory it is possible.
So again in my mind, generally going slower in EV will get you more available EV miles and generally be more efficient than driving in EV at higher speed, for sake of argument such as EV at 84 mph which is the Primes EV only cut off mark. Run the numbers at both very low speed and very high speed and it should become more clear, minus all the other variables at play during a regular drive to work or town.

 

There's something else to remember, the ICE is more efficient at slower speeds as well...

 

It might be an interesting assignment for someone interested in getting the engines real world efficiency curve
and listing all the variables encountered while getting the results.

I haven't looked closely, but I'm thinking the engine at - very low - speeds is not it's most efficient area.

It's much easier to tell ( do in part to it's limited availability in Prii ) in EV how much of a difference such things as wind resistance at higher speeds, strong head winds, cold weather, rain or water on the road, etc effect range and / or efficiency.

Just wondering, if the power split was opposite ( bigger motor and pack with a small engine that also powers the wheels ) if it would be easier to measure the engine efficiency than it would be to measure the motor efficiency as a driver in real world scenarios

 

It depends on what you mean by very slow speeds, but I can for sure say that I get better mileage when going 30 than when going 50, and by a decent margin. The real time MPG is just as much a hint as to efficiency as to what you're using to figure out your EV efficiency. Maybe a tad slower, but it's there. I think we're both on the same page about maximising EV to maximise total efficiency, but it's not always easy to find the best way. Trial and error is how I did it.

My commute: Start, putting it in HV mode immeditaly, then about 15 miles at ~67MPH (at the coldest time of day too), a town, then 22 miles rural highway at 62. No charging at work. Leave work in EV mode and run it until it's out, which happens to be in the same 15 miles streatch as morning at 67 MPH. I've gotten up to 114MPG on that run, but average in the low 90s, depending on speed anywhere in my commute. The slower the better, the faster the worst unfailingly.