My 2015 one did poorly in deep snow. After one winter I traded it away. I think weight ratio between front and rear is off(too much weight in the front). In deep snow rear wheels float up instead of digging in. Other vehicles I had did not do that. Acura MDX, BMW X5, Audi SQ5, Benz ML550 under same condition. IMO, the OP's test does not really simulate deep snow condition.

 

And none of you asked, what happens when hybrid battery is low... and you must have AWD... where's juice for it coming from then....

 

 

Simply not a good car for cold climate. I had it for 1 year and went back to regular AWD car. When cold fuel saving goes down a lot too.

 

 

This shouldn't happen unless there is an issue with the charging system. At that point, it needs to be looked at.

 

Agree with your tire opinion. The tires were developed for MPG, all other capabilities are secondary.

I will say this. I was originally looking at Highlanders (none to be had, another story). Anyway, some of these video bloggers tested one for its AWD snow capabilities and it did fairly well. I will go out on a limb and say it with the right set of tires, snow performance should be adequate. But as usual, individual results my vary.
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Charge/discharge occurs simultaneously = Float charging.

 

on the 3rd gen RX, the normal mode has the rear drive motors engaged until about 22mph. In the snow mode, the rear motors are engaged until about 40mph. but the throttle tip-in is super slow. Obviously you are not driving fast in the snow.

 

Ok, let me ask you this. You are at 2 bars on battery gauge. Which is nothing abnormal. And you MUST have AWD kick in. Will it have enough whoomp to power both front and rear electric motors? Ah, say you, ICE will kick in, right? But ICE charges battery, not provides power to MG.
It's hypothetical though plausible situation... As battery charges slowly and rear motor depletes it fast. OR, it simply does not engage and front only is prioritized. So you lose AWD.

 

You can tell me, based on this simulator:
http://eahart.com/prius/psd/

Can the ICE generate enough power to spin the rear motors? Looks like it to me.

 

I don't have the RX, but have the Highlander Hybrid and spent a lot of time in the snow these past few weeks. It performed phenomenally. The rear wheels were always powered from a stop, so they didn't need to wait for slipping to happen. They stayed powered until about 20mph.

Since I was driving slow - around 25 mph due to conditions, I was on electric power a lot. I was somewhat concerned that I'd run out of power to drive the rear wheels but that never happened. Once I got down to 2 or 3 bars the engine would kick in to recharge, so I never found myself in a situation without battery power for the rear.

I am not sure if the RX450h is any different, but I sure was impressed with the Highlander in our 8" of snow. It drove very similarly to my 3rd gen RX350 AWD, which is to say, despite snow and hills, and lots of stopping and starting, I never had any traction issues, despite cars all around me struggling to get moving.

 

Heading up the mountains to Keystone from Denver to go skiing a few weeks back I saw lots of cars struggling to make it up a high incline area while my 2016 RXH handled it just fine, no slipping, no issues whatsoever despite stopping and starting on multiple occasions. Overall comparing it to other SUV's I've driven (GX470, Q7, Highlander AWD) I'd say it's easily on par for the best of the bunch in snow/ice handling and that's with stock tires. Disclaimer: I have not yet experienced snow over 8" with it.

 

I think you might be overestimating the power draw from rotating the rear wheels. Forget the hypothetical AWD mode. A far more common scenario for your example is If you put the car in reverse. Remember, only the rear electric motors are in play when backing up; and when was the last time you heard of a hybrid driver not being able to back up due to their batteries running low?

Pretty sure the engineers would have accounted for keeping enough battery power to allow for a simple maneuver like backing up into a parking spot; which would likely need more power than the occasional burst of AWD mode from the front wheels slipping.

 

Not true. I live in the Colorado mountains (Grand Lake) and have never had a problem driving through snow up to 12 inches. I never have felt the tires spin in deep snow, so I can’t say if there is any hesitation, when the motors kick in. When the snow gets pounded down to packed and very slick snow/ice, I can feel the front start to spin when moving from a stopped position on a hill, but then I feel the rears kick in and keep the car moving very well. I have the OEM tires on it, which are all that is needed to drive on graded or paved roads. It is not an off road vehicle, so the need for 4WD vs AWD is not required. My wife has a 2016 RAV hybrid and it goes equally well in snow/ice. She also has the OEM tires (all season).