What powers Prime HVAC in winter?

the HVAC is an independent unit. It is electrically powered. It does not care whether the car is being pushed by gas or volts.

Earlier models of the Prius have included PTC (resistance) heaters in the defrosters for absolutely instantaneous heat. Not a lot of heat mind you, but it really does accelerate the overall process. I expect they will do the same for the new model.

Once it is cold enough, the car is just going to start the engine based on demand for heat. And why not? Burn some gas to heat and move the car out, then use your battery to come back home.

 

prime has an electric heat pump, instead of resistance heat. it is much more efficient and doubles for cooling and heating.
you don't need the engine down to the temps you mention, but as it gets colder, it is less effective and at some point the engine kicks on.
then you have to wait a few miles or minutes for engine heat, but it doesn't take too long.

in maryland, it should work pretty well for you

 

I'd hate to think that you have owned such cars in the past. I had a 1968 Oldsmobile that took forever to provide heat to the cabin. I only had a 6 mile commute to work, so it was not really worth turning the heater on. I wore gloves and a parka in the morning.

But that was 55 years ago, when the cars still had carburetors and chokes to make the fuel mixture richer in order to start it. Those were the days when a lot of the non-essential engineering was based on "well, that worked OK the last time we tried".

Once you try actually driving a Prius, you will probably be quite pleased at how well it does what it's designed to do. Note the wording. It does what it's designed to do well. It's not designed for hauling trailers, so don't expect success when you find there is no place to install the hitch for a 20 foot long third wheeler. But I have the 2017 model and can assure you that it quickly provides heated air shortly after turning on the climate control.

 

That's true for your moderate climate conditions.
Heat-pumps are a very complex and involved topic. Much more so than even Air Conditioning.

Until the Gen5 Prime specs and uses have become available, no one can say how the heat-pump system will work in a Gen5 Prime, in any condition (temperature, humidity, etc).

Just look at the specs and designs of heat-pump systems.
In general, PTC (like the home ceramic heaters), provide heat much faster, and under wider (colder) conditions.
However, heat-pumps are often much more efficient, especially in temperatures above 35F (above freezing).
Below ~35F, to get heat-pumps to work, and to gain efficiency, it takes cost and weight.
You won't find many people in Florida spending the extra money for a heat-pump systems that provide heat at -30F.

For the Gen4 Prius Prime, imho, the heat-pump is okay down to ~50F outside temperature.
Imho, without direct sunlight (e.g. unheated detached garage), by the time the outside temperature gets below ~45F, it becomes near worthless.
Example, at ~35F, it can take 30+minutes (3 or more remote cycles), just using the "remote temperature control" and the heat-pump, to defrost a window. Yes, defrost. (e.g. car outside during the winter)
If someone has to ask why defrost at 35F, then they should google how that big yellow thing in the sky, effects the daily temperature cycle.
I also picked 35F, because, in general, most heat-pumps work pretty well above freezing (actually "X-degrees" above freezing ).

Note, every heat-pump system, especially for EVs and PHEV is very unique.
Saying "heat-pump" as a generic heating ability, is even more incorrect than saying "window AC", considering that you can get a window AC between 2K BTUs (some hose-based 'portable systems') and 40K BTUs.


Fwiw, for the Gen4 Prius Prime, with it's small(low in mass) and very efficient engine (different then the Gen5 engine) and exhaust heat-recovery system, when the engine is started the first thing in the morning, the cabin heat starts very quickly and so does the windshield defrost.
Still, next Summer, I'm likely putting in aftermarket remote that starts the engine, and turns on the front defrost (~$1,000+, installed). Note, the aftermarket remote start system works for the Gen4 Prius and Gen4 Prius Prime.
For any Gen5 Prius, any aftermarket remote start system will require a different interface and programming. If/when an aftermarket remote start system will support a Gen5 Prius is unknown.


Good Luck with you upcoming purchase - enjoy!

 

Air Condition performance and Heat performance, are design/cost decisions that must be made for every heat-pump EV and PHEV system.

Air Condition performance on the Prius Prime, is very different than the heating performance.
For high-end EVs (e.g. MB EQS), they will both be very good.

For the Prius Prime, the Air Conditioner functionality (of the heat-pump system) is powered only by the hybrid/traction-battery.
So, with a fully charged battery, or a hybrid-battery charged above ~10%-15%, the gas-engine has no effect at all on the Air Condition performance.
Once the hybrid-battery gets to ~15%-10%, the gas-engine will be used as a generator, to charge the hybrid-battery, as needed.

I don't live in a very high heat area (like Phoenix, Las Vegas, etc), nor a very high Dew-Point area (like at the equator), nor near the equator (stronger sunlight).
So, I can only comment on the Gen4 Prius Prime Air Conditioning performance in regards to a max of ~105F, ~72F Dew Point, and with a New England latitude.

Imho, for New England (Conn coast to Northern Maine), *I* have found the Gen4 Prius Prime AC performance to be awesome!
Oops, I wanted to add, that I use a CoverCraft, close fit, custom sunshade. And, I have vent shades. And, when no rain is expected, I'll also use black mesh window shades (I got the idea from Nikki and Camper). For me, parking at work and home is safe, so I don't have concerns about people breaking in the Prius. Also, a Gen4, with Toyota's new smart fobs, would be very hard to steal.
Btw, keep your key fob in a good Faraday case (e.g. Silent Pocket), or far enough away from any outside wall.


Imho, the Greater Phoenix area, is one of the most challenging cooling areas(population wise) in America.
Yea, yea, Death Valley may be more challenging cooling location. But, according to Google:
"More than 300 people live year-round in Death Valley, one of the hottest places on Earth.".
I take that to mean, that a big apartment complex in Phoenix likely has more people than all of Death Valley. Of course, that's just a guess.

From: Tides on 71st - 7007 W Indian School Rd Phoenix AZ 85033 | Apartment Finder
Tides on 71st is located in Phoenix, Arizona in the 85033 zip code. This apartment community was built in 1986 and has 2 stories with 1012 units.


Good Luck!

 

I'd watch this video.

 

Weird. I have a 2017 Prime, I live in Colorado, and my heat pump works well, effective in 30 seconds or so, right down to 12F.

 

Depending on your parking situation you may be able to preheat the cabin, say running a 120 volt AC cord out to an electrical heater in the car. Taking advantage of grid power lessens the needs imposed on the car.

With our 2010 hybrid we similarly use a block heater.

 

Very weird!
How about other Gen4 Prius Prime owners?

I have a number of different parking situations.

• unheated detached garage
• outside at night
• outside at work
• outside, upper level garage, at work
• "outside", lower level garage, at work

It's the same in each case.
When it's below ~40F, regardless if it's in the morning, or going home in the afternoon, even though I always Toyota App "pre-condition" (for ~5-10min), the first thing I do after I turn on the car, is to put the car in HV mode, to get some heat and to defog/defrost the front windshield.

As for the rear window, my Gen4 Prius Prime, using the Toyota App "pre-condition", does an average/good job at defrosting/defogging the rear window.
It's the cabin temperature (almost the same, when it's below ~35F), and the front windshield that are just about the same.

 

Thanks to your suggestion, I did get a block heater.
However, I haven't yet had a chance to install the block heater.

Also, so far (lowest in the teens), using my engine, I get heat amazingly quickly!
Imho, I'd say the closest car would've been my ($50 ) Chevy Vega, with it's 140CID 4cyl all aluminum engine, running rich, with no cats to suck up the start-up heat.

 

Don't put if off, it's so much fun to install... Kidding...

One tip: hold off applying the heat-transfer grease till you've managed to dry-fit the heater element. in the recess. It's NOT easy getting it there; there's so much cr@p in the way. Then back it almost out, apply the grease (probably from below the car, purely by feel, impossible to see what you're doing), then ease it back in. Try to rotate it as it goes in and keep it centred, to avoid scraping the grease off.

Honda's have an easier system: there's a large diameter bolt on the the engine block for coolant drain. The block heater is a similar bolt, with the heater element embedded. Much easier access during install, and the heater element is in the coolant, no heat transfer grease to fuss with. I'm leary of Toyota's system too, suspect the heat transfer grease may vapourize over time. Who knows.

 

As pointed out, the heat pump is electric, so its operation is independent of the engine's.

As the heat pump name implies, it works by moving heat around. For heating, it is basically an air conditioner in reverse. How well it heats depends on how much heat is outside. Colder out, and it needs to work harder and longer. The gen4's spec was able to provide heat with out side temperatures down to 14F or 15F. How well it does so depends on local conditions and individual preference.

Below those temps, and the car will turn on the engine for heating. It might do so for something else, like the battery, being too cold during winter. It will also turn it on for the front defroster. That job needs warm, dry air, something a heat pump can't provide well on its own.

I think it's a safe assumption Toyota will use the same heat pump in the new Prime as the old.

Heated seats and steering wheel do help out.

All my cars in the past twenty years were able to start heating the cabin within the mile it takes to get to the highway, without idling at start. Leaving the heat off until the engine reaches operating temp speeds that up.

 

what do you mean gen 4 prius prime owners? 2017-22 are gen 4.

 

The G4 Prime heat pump is quite the beast. See: How does the heat pump work in a Toyota Prius Prime plug-in hybrid? (greencarreports.com) for an explanation on how it works. My 2017 has worked fine in temperatures below 20 F in my mid-Atlantic location.

I seem to remember when I got the car a description that there was an engine coolant circuit to steal some heat from the catalytic converter to warm the engine more quickly if it did need to come on. The catalytic converter comes to temperature in seconds and can spare some heat to help out. I expect that is why if the engine is needed for heat, it is available faster than in my previous cars.

 

Correct.
Iirc, the Gen3 PiP had a PTC heater, not a heat-pump.
Plus, it's reasonable to assume that Toyota would update the heat-pumps between generations. Heat-pumps, especially automotive heat-pumps, are rapidly advancing.
Like with hybrid/EV battery technology, the older technology is often not the best "bang for the buck", nor is it often is even the cheapest.

Fwiw, for a Tesla Model 3, in sub-zero weather, the older PTC heats faster until ~~40-50F inside cabin temperature, verses the new heat-pump systems.

Code:

https://www.youtube.com/watch?v=4CHF0sKPQiU
Model 3 Heater Race! Heat Pump vs PTC In -20F
Out of Spec Reviews
Dec 26, 2022 
Kyle and Alyssa freeze their asses off for yet another cold weather test! This time they race the PTC resistive heater in a 2019 Model 3 against a 2021 Model 3 with a Heat Pump

 

The old Prime's heat pump is an impressive unit. It's why I don't think Toyota is going to spend more to change it for the new.

The gen 3 Prius got an exhaust heat recovery system that heated coolant off the upper exhaust pipe for faster engine warm up. It continued into the gen 4. Is that what you were told about?

 

On the Gen4 Prius (and Prime), after the first catalytic converter, there is an in-line heat-exchanger in the exhaust.
See:
Engine coolant inside catalytic converter | PriusChat

The Gen3 Prius had a similar setup (but not exactly the same).

 

... which is pretty much what any Prius's HVAC "auto" mode will do: you'll notice the in-cabin blower being off at first, and gradually ramping up as the coolant comes to temp.

The heat exchanger for that is downstream of both catalytic converters, so it doesn't "steal" any heat from them, really. Some of the heat it's collecting will be heat the reactions in the converters produced. You're only depriving the muffler and tailpipe of that stolen heat, which nobody was counting on anyway.

In Gen 4, that heat exchanger also has an unfortunate reputation for stealing coolant, too. Maybe it's trying to give the muffler and tailpipe something in exchange for the heat it deprived them of.

 

The Gen4 Prius Prime heat pump is a very old and very expensive design, it's "obsolete".

The Gen5 Prius will likely go to a newer heat-pump system, like the one that the Rav4 Plug-In uses.
It's "unlikely" to be the same exact system as the Rav4 Pug-In, since the Rav4 has a much greater heating/cooling BTU requirement, and the Gen5 Prius is already significantly more expensive that the Gen4 Prius.