EV mode is wasteful / less efficient on the highway - Misconception

shmoo11 · Feb 24, 2021

I've heard people in a number of places talk about driving in EV mode around town or whatever and then when getting on the highway, putting it in HV mode because EV mode is less efficient on the highway, or should I say at highway speed. I don't get this logic and I think it is based on a misconception, but I'd love to hear other thoughts...

Yes, ev mode on the highway is less efficient than it is around town. The same goes for HV mode. The faster you drive, the more drag the vehicle has to contend with, and it is non-linear meaning doubling your speed requires much more than double the power to overcome the increase in drag. The source of power that moves the vehicle forward has nothing to do with this. You will get fewer EV miles on the highway than around town in most cases, but the same goes for HV miles. If you have a 100 mile trip, 50mi on the highway and 50 miles driving ~40mph off of the highway, you're going to use roughly the same amount of (combined) electricity and gas no matter how you split up the EV/HV driving.

The only exception I see here is that if the engine is running, you're not consuming extra energy to heat the cabin since you can use waste heat for that from the heater core.

Now I do still believe that AUTO EV/HV can be worth running on the highway for longer trips. This allows the car to pull less current from the battery by using the engine to assist under high loads, which is better for the battery and requires less use of the a/c to cool the battery.

CH420 · Feb 24, 2021

I would not say that EV is ever less efficient at any time. But with a limited amount of EV (battery availability), I run the ICE on the highway because it is more efficient at highway speeds relative to stop and go in town traffic. If you have more than enough battery capacity for your entire trip then I would run EV for the full duration. My understanding is that AUTO EV/HV gives preference to EV and quickly depletes the battery. I never use that mode. I’ll select either EV or HV manually depending upon trip length and driving conditions.

shmoo11 · Feb 24, 2021

ICE in a hybrid setup, just like with an EV, is generally more efficient in stop and go and city driving than at highway speeds. Non-hybrid ICE powertrains are more efficient on the highway than in stop and go. AUTO EV/HV does give preference to the battery but uses the engine in cases where more power is needed, which seems to make sense.

michaeljeff said:
It’s actually pretty simple. The 42 miles estimated from EV applies to low average speeds. If your average speed is 70+ then you might only get 30 miles on a charge. If you travel all low speeds, you might get 50 miles on a charge.

The efficiency is the same for gasoline, the faster you travel, the lower mpg you get.

Agree totally, what seems off to me is the idea that switching between ev/hv depending on highway or regular roads makes some kind of sense. If you're taking a trip that is long enough to deplete batteries, I think the amount of gas you use will be roughly the same no matter when you use ev/hv. If you're taking a trip that won't deplete the battery, I see no reason to use hv mode unless you're in situations where you will encounter high engine/powertrain load, in which case auto ev/hv seems like your best bet.

michaeljeff · Feb 24, 2021

It’s actually pretty simple. The 42 miles estimated from EV applies to low average speeds. If your average speed is 70+ then you might only get 30 miles on a charge. If you travel all low speeds, you might get 50 miles on a charge.

The efficiency is the same for gasoline, the faster you travel, the lower mpg you get.

Illinibird · Sep 23, 2022

This is exactly the question I was going to pose. On a full charge my EV range is only 35 miles and I thought maybe something was wrong. Now I think I understand that the GOM (guess-o-meter) says 35 miles because we have used the EV mode mostly at highway speeds so far. My assumption then is if we had used the EV mode mostly around town, the GOM would say the range is closer to the 44 miles which is advertised on the window sticker. Am I correct in this assumption as per the above post?

RussC · Feb 25, 2021

Electric for me is half Dino Juice

We just filled our Prime gas tank after 6 months ownership.

I drive to work 56 miles round trip 70 - 85 mph in EV and cold days 2.0 -2.2 miles per kWh

Lately with temps in the upper 40’s low 50’s I have been hitting 2.6-2.7 miles per kWh.

Last Aug when we purchased the Prime I consistently hit 2.8 per kWh and I drive fast

Around town driving 30 mph I can get 3.2 miles per kWh.

I have nothing to compare but 2.7 miles per kWh is $1.31 to travel 39 miles compare to gasoline the same distance I am half the cost Dino juice.

cometguy · Feb 25, 2021

HV mode makes sense when you're driving outside of your battery range and driving > 40-45 mph. EV makes sense when you're driving < 40 mph, while you're driving within the range of your battery. Auto-EV/HV makes little sense at any time, because it runs in hybrid mode but runs the battery down very quickly; it might make sense if your drive between charging is like 50-100 miles, but makes no sense if your distance is > 100 miles. HV essentially runs in hybrid the most efficiently, keeping the battery at about the same charge level, when driving long distances. Yes, the air drag on a car increases exponentially as your velocity gets higher and higher, but because we have very limited energy through our 18-kWh battery pack (compared to our 14.5-gallon gas tank), the electric driving takes a big hit much more quickly at high speeds, and ICEs tend to be much less efficient than electric motors in slow, stop-and-go traffic. So drive in all-electric at slower speeds, and drive in hybrid (HV) mode at faster speeds. You don't have to touch any buttons on a long road trip, and the car will just go into "Auto-EV/HV" mode once your battery is drained (which will be very quickly on a long road trip). I will routinely use EV mode at up to ca. 83 mph on the expressway locally when driving short distances, within my EV range, simply because its much more enjoyable to drive in electric mode than with the ICE on (at any time), even if that drains the battery much faster -- but that's just me. If I have to drive 40 miles on expressway, I'll just put it in HV mode when I get to highway speed and then pop back to EV mode when slowing down again; this way I almost always have plenty of battery for that stop-and-go slow traffic.

shmoo11 · Feb 25, 2021

I'm a bit confused by this, I'd think HV mode makes sense when you're out of battery power or want all 300hp, otherwise EV mode makes sense. Auto-EV/HV does not "run in hybrid mode". It runs in ev mode but uses the engine occasionally when more power is needed, i.e. you give it a lot of gas or you're driving fast up a steep hill. It lets the powertrain computer decide when it is best to add engine power. ICE engines only have this inefficiency in stop-and-go traffic when they are configured in non-hybrid powertrains. As a hybrid, the engine is not less efficient in stop and go traffic...

You can't be in auto ev/hv mode when the battery is drained, when you run the battery down you are automatically put into HV mode.

rsl360 · Feb 25, 2021

I feel like I have to defend Auto-EV/HV. It gives you the full power of the car, and yet you can tool around mostly in electric mode. Imagine that the RAV4 was a sports car. It would make a lot more sense. 302 hp at every traffic light and stop sign. And yet quite and serene gliding along the rest of the time. I agree it's not that useful to most of the present owners. But I think that's becasue we are not the right market segment. Also, if you think about it, Auto-EV/HV is really just a few lines of code. It's not like there is a ton of expensive hardware.

RussC · Feb 25, 2021

If you drive less than 40 miles EV which in my case is 90% of my driving.

If I know my trip will be more than 40 miles I just run the EV dry and let her switch to HV and enjoy 35 -37 mpg freeway driving.

Wind and outside temperature , I have found knocks my EV range.

The heat pump draws 30 amps and until things warm up my range is 1.6 miles per kWh.

After the heat pump has warmed things up after a few miles the range settles in around 2.2 miles per kWh if it is cold outside but when temps are above 60 F I easily get 2.7 miles or 39 miles of range driving 70 mph

cometguy · Feb 25, 2021

CyprusCorner · Feb 25, 2021

Another reason it's worthwhile to save EV for city driving is that EV mode will prevent the engine from turning on as much. Most city driving is stop and go, and sometimes leaving the car for 5+ minutes to run errands. If you can reduce the total number of warm ups the engine experiences, you're going to gain a lot of efficiency.

Billyk24 · Feb 28, 2021

Has anyone measured/documented battery temperature while driving in EV at high speeds (freeway-up long hills)? There is a limited number of battery cells and the speed(stress) placed upon these limited number of cells may cause temperature increases beyond what one really wants for longevity purposes.

NoelinColorado · Nov 2, 2021

I don't see this as an issue, using EV mode for freeway speeds at least in the 65-70mph range. It takes huge input of energy to accelerate to 65mph (compared to 0-30mph, about 4x more to go from 30 to 65mph), but maintaining that 65-70mph doesn't require all that much input--just observe the power meter on the left side of the display--it's typically right in the middle of the Eco range, at least on the relative level.

wscan · Sep 23, 2022

You are pretty much correct in your assumptions. Your car is new and the GOM starts with a low EV estimate. You will probably see some increase in the GOM after a few weeks, assuming that you drive at 70 or below. If you are a high speed driver, the range probably will not increase much.

newrav4p · Sep 23, 2022

I set my R4P to show miles/kWh per trip. Multiplying that number by 14.5kWh for the "usable" portion of the battery yields the expected mileage range if that type of driving is done until the battery is depleted. Sometimes I get 2 miles/kWh, which comes out to around 30 miles. A few times I've seen 5 miles/kWh, which comes out to about 70 miles! The EPA rating of 42 miles assumes 3 miles/kWh.

RussC · Sep 23, 2022

I drive to work on the interstate with a full charge nearly 28 miles reaching speeds of 85 miles per hour for brief periods of time in EV and generally averaging 75 miles per hour in EV.
Looking back at my Charge Point data 10.5 kWh has been the highest and most have been 10.1 kWh charges to travel 28 miles.

28 miles / 10.5 kWh = 2.66 miles per kwh

I have 14.5 usage kwh x 2.66 = 38 miles of range averaging 75 miles per hour with a few bursts to 85 mph.

Note: This is my most inefficient usage over the last month. The average of 10.1 kWh for 28 miles averaging 75 mph is 40.1 miles of range which is pretty good considering I am averaging 75 miles per hour over 28 miles.

Winter driving in Utah (already have been through two Winters with temps in the 20’s and 30’s) the range will drop 20% or 40 miles of range to 32 miles interstate driving at 75 mph. The heat pump pulls 30 amps and you will know when it is on when you hear a loud train horn sound on occasion when first operating in EV.

My recommendation, lower the cabin temp set the defrost on the control near the right side only (don’t tough the defrost on the left gas will turn on) set seat warmer to low and if needed turn on steering wheel heater and use my invention which is a silicone kitchen cabinet bumper placed on the steering wheel heater control so you can feel to turn off and on. Toyota placed that control in a hard to see location while driving.

I also dress warm with gloves when I drive in the winter with the cabin temp set low.

Russ

wscan · Sep 23, 2022

RussC said:
The heat pump pulls 30 amps and you will know when it is on when you hear a loud train horn sound on occasion when first operating in EV.

The train horn issue can be fixed. There is a TSB out.

RussC · Sep 23, 2022

Cheap but works

newrav4p · Sep 23, 2022

This link has some interesting power efficiency and relative range versus speed curves. Even though the curves are for Tesla, I'm guessing that the shapes of the curves are similar for R4P. Essentially, max efficiency or range is achieved somewhere around 35-40 mph. EPA numbers are usually at 55 mph, which can be anywhere from 5-15% lower than max efficiency/range. At 75 mph, the drop-off relative to 55 mph can be 15-25%.

Salmon · Sep 24, 2022

I drive mostly in EV because most of my driving is short trips. When I drive 100 miles RT to my daughter's house I drive to the Highway and get up to speed in EV then switch to HV on a downhill section and leave it there until I get off the highway where I switch back to EV mode. On the return trip I do the same except I switch to EV once I am close enough to home to almost drain the usable charge. Why do I do this?
1. The ICE is needed for the trip so I would rather run it continuously than on/off/on/off.
2. EV is quieter than HV but that is only noticeable at slower speeds since road noise generally makes the ICE less noticeable.
3. This method drains the EV charge level down from MAX fairly quickly and leaves it well above MIN until I am almost home. I have heard the more the SOC stays away from the extremes the better it is for the battery.

As for what is most efficient I don't know and I doubt it makes a very big difference. But people like to argue about that so have fun. I am sure there are holes in my strategy but that's what makes the most sense to me so that's what I do.

Illinibird · Sep 24, 2022

This is a newbie stupid question but here it goes anyway. When we drove to where we volunteer each week (about 38 miles away) the RAV4 had a 100% SOC and the drive was set to Auto E/HV. For the drive there, we used 100% EV and were on the tollway with speed limit of 70 mph. On the way home, the car started out in EV but after a mile on two the car switched to HV and remained on HV the entire high speed (70 mph) home. Our overall mileage was high but I didn’t record it. Now my question: isn’t this the way one usually runs the plug-in hybrid? If not, and many start out only in HV what button are you pushing to force HV only from the start of your trip? Is it the HV Charge button? On the EV button it either is EV or Auto EV/HV correct? Does the HV Chg button change with the number of presses from HV Charge to just HV? I know these are probably dumb questions and I should know but I’m really unsure how you force HV mode and whether using Auto EV/HV isn’t the way the car is intended to be driven on long trips. It eventually would run on total HV once the SOC on the chargeable traction battery is depleted on the SOC gauge shows 0% so why “force” your car to use just HV on the highway and keep the SOC of the battery high for when you arrive at your destination where you could then switch to total EV? If you had used up all your EV charge and the car then runs in HV at your destination what harm is there in that until you have a chance to plug-in again at your destination (or overnight at a friends house or hotel on 110 volt outlet or lucky enough to find a L2 EVSE and replenish there for 4.5 hours). I’m trying to understand everybody's strategy for running the cars efficiently with the settings people use for different driving. I thought I had this figured out but after reading this thread I’m not sure that I do.

old timer · Sep 25, 2022

In 18 months of driving the Rav, I have never had an issue with acceleration. For the most part, there is plenty with just the EV. That includes many miles on I5.

NoelinColorado · Sep 25, 2022

I'll stick with warming up the ICE by departing from my garage or other parking area when it's cold and I can warm it up sufficiently at low to modest speeds, because there is no compelling reason to do otherwise. Certainly won't switch to HV mode because I'm about to enter a freeway, when the ICE hasn't warmed sufficiently. There is no good reason to.

Hey anyone w/ a HUD: go from a cold ICE into HV mode just prior to entering a busy freeway onramp and describe how the RPMs behave it would be telling to actually know. And to be useful--give it plenty to see at what point the ICE kicks in, if it does.

chuckles70 · Sep 25, 2022

I do it all the time. Engine doesn’t rev until it’s warmed up unless you give lots of skinny pedal. Way more than normal acceleration to get it to rev.

Sometimes i misjudge EV range and ice kicks in just before I get home, and I have to climb a super steep hill. Same situation, engine doesn’t rev despite being well into the power band on that climb.

IMO this just isn’t something to worry about. The car will take care of itself, within reason.

NoelinColorado · Sep 25, 2022

I don't worry, I just do what makes the most sense and it completely fits with how we use the car. No matter how the car was engineered to cope with short, sporadic use of its ICE I really like the idea of discreet uses of it to fully warmed up. This approach leads to no inconvenience whatsoever, so there is no downside, only upside. The other reality is I'm sure Toyota factored in the fact the ICEs in plug-in hybrids do not need to go 200K miles as they simply, on average, do not get used nearly as much as their all-gas counterparts do. If they go 75K miles that's amply enough in fact it's probably way longer than it needs to run.

wscan · Sep 26, 2022

The ICE in the Prime is the same engine that is used in many of the larger Toyota hybrids: RAV4, Sienna, Highlander. I am sure the engine is built to go well over 100K in those vehicles. The Prime is based on the same firmware that those hybrids use. From my experience in the Sienna, the ICE also starts and warms up at 1300 rpm. The traction battery is used to power the car until it warms up, you really step on it, or the traction battery runs too low (which happens more often in the Sienna with its 1.9 kWhr battery vs. about 4.5 kWhr in the Prime that is reserved for HV mode).

NoelinColorado · Sep 26, 2022

It's somewhat of a moot point anyway as I say because many just won't put a lot of miles on the ICE. I'll continue to practice what I preach as it's easy, makes sense and I know it will most likely be significantly kinder to the ICE than disregarding these fine points. Remember--the main issue focused on how important/useful/etc is it to turn HV mode on as you enter a freeway onramp on a cold engine. There is really no good argument for doing this anyway--as Chazz mentions he starts his at the top of a long downhill so the engine isn't revving excessively when cold--it happily ambles along at said 1300rpm.

Chazz8 · Sep 27, 2022

NoelinColorado said:
as Chazz mentions he starts his at the top of a long downhill so the engine isn't revving excessively when cold

^I never said that. I live at the bottom of a hill. When I start in HV mode from home going up hill, I feel/see acceleration/power, but ScanGuage and OBDLink say that ICE stays with cylinder fire timing value of 5-6 (I read that means at top of stroke = min power but good heat) and all (locomotion) power coming from EV systems.

I have tried to force ICE on by flooring it on a cold winter morning in EV mode. The R4P stopped accelerating when it hit the POWER tick and would not send the needle into the POWER zone. I will try to force ICE on in HV mode with ICE in warm-up cycle today. I don’t think it will turn on, but we don’t know until somebody does the experiment.

chuckles70 · Sep 26, 2022

Those millions of ICE only drivers traveling billions of miles every year on cold engines. Crates upon crates of spare engines stacked up at the dealership to rectify the ensuing carnage. Most cars north of the Mason Dixon line tapped out after 75k miles.... Oh wait...

It's the same myth as idling. https://www.washingtonpost.com/news...9/the-biggest-winter-energy-myth-that-you-need-to-idle-your-car-before-driving/

So a lot of us are greenies, bought the car to cut CO2. But we don't trust the Toyota engineers that they thought of the warmup cycle so we do just a little "extra". That "extra" is many tons of CO2 across the fleet / time.

EddieJoe · Sep 26, 2022

Perhaps I have read the other posts incorrectly, but I’m not interpreting them as advocating long idling to warm up the ICE prior to operation. If that is what you are reacting against, I think you are mistaken. Prior reading on my part, and the ensuing choice I made with my previous ICE engines, was to start the engine, give it 15 seconds or so to let the oil circulate, then proceed in gear and drive normally, but avoiding hard acceleration for a few miles while the engine warmed up. This procedure was described as the best to rapidly warm the ICE and avoid long idling, thus saving fuel and lessening emissions.
The circumstance folks are concerned about is going from EV to HV at either higher speeds or higher throttle, essentially putting the ICE under heavy load with little warm up at all. One can (I’ve done it once, when testosterone crazed) when in EV, punch the EV/HV button to engage HV, twist the Sport dial, and floor the Prime. It doesn’t remain @ 1800 rpm, it goes like a bat out of hell. So, most of us, when contemplating using HV, which for me is going out of town, start out in HV, drive at normal speed, and essentially warm up the ICE while driving it , but NOT at a high load.
That’s it.

richguess · Nov 5, 2022

I’m surprised by how much the mileage drops as speed increases. Our Touareg diesel got 30 mph hwy at 75+ mph. Our R4P drops from near 40 mpg to 33 mpg at those speeds. The hybrids don’t like high hwy speeds. Our Ionic 5 range drops with those higher speeds too, but when just driving locally, and putting it in sport mode, it’s a real pocket rocket. 0-60 in 4.5 sec.

EddieJoe · Nov 5, 2022

It’s not because hybrids don’t “like” highway speeds, it’s because at highway speeds the ICE is running nearly all of the time with no EV assistance, and the ICE is the same one found in the regular model but pushing a heavier vehicle (battery weight). Overall mileage is also affected by no regenerative braking at steady higher speeds. Diesels get about the same mpg regardless of speed.

wscan · Nov 5, 2022

The reason hybrid mpg drops more at high speed is that the high mpg is a result of the ICE being able to shut off at times. Higher speeds reduce the amount of ICE off time thus reducing mpg.

NoelinColorado · Nov 5, 2022

Yes and the obvious increase in drag which is substantial and why all cars lose mpg at freeway speeds on up.

BGA206 · Feb 26, 2023

^ Something else must be causing your engine to turn on, it isn’t the 18mph threshold.

moapys · Feb 26, 2023

I found my answer after posting; we don't have a "Prime" apparently: 84 miles per hour on EV mode in a RAV4 Prime, and approximately up to 25 miles per hour in the RAV4 Hybrid.

CoffeeBear · Feb 26, 2023

Reading through this thread it's mentioned that auto mode gets you the full 302hp. I assumed hv mode also did this. Is that incorrect?

I get why ev only would not. And maybe also charge mode. But auto or hv seem like they would both potentially have full power on tap. Can anyone enlighten me here?

SDGTR · Feb 26, 2023

I have no way to measure actual hp but in Auto and Hybrid modes it does feel like I'm getting full power when I nail the gas pedal. EV mode is significantly slower. I've been driving in EV mode when I have enough charge but I actually prefer Auto because it will run in EV mode when the car thinks it's more efficient but also has the full power on tap if needed in a situation in which it is necessary or helpful. Merging onto a freeway with a short on-ramp in rush hour traffic is much easier with the full 302 hp.

EV mode is wasteful / less efficient on the highway - Misconception

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