gen5 prius phev reliability/TCO

Toyota hybrids(including plug-in hybrids) are generally the most reliable and lowest cost of ownership vehicles around. With the caveat that I'm speaking of regular Toyota hybrids, not the Hybrid MAX and i-Force MAX hybrids on the trucks and big SUVs.

I'm going to lightly ask whether a PHEV is really right for you and not a HEV or BEV, but that's a question you need to answer yourself, and it seems like you might have.

Since you say you don't know much about hybrid powertrains, I'm going to give some basics. This is the internet, so I'm sure others are going to disagree on particular points. Listen to all of us, do some of your own research, and then listen to the real professionals. I recommend TheCarCarNut for maintenance/repair info, and Technology Connections for overall hybrid powertrain info. Weber State's(WeberAuto) videos on the hybrid system are great, but they might be too in depth for someone still learning the basics. But up to you.

The internal combustion engine on a hybrid can be just the tiniest bit less reliable than a non-hybrid. That's because the more numerous start/stops of the engine can cause issues with the engine oil. Mostly fuel dilution and an increase in stuck piston rings. This can be solved/avoided with regular oil changes(6m/5k mile) no matter how much or little the ICE actually runs. People who work on these engines for a living say that the less the engine is used, the harder it is on the oil. There's also the choice to use a cleaning oil like Valvoline Restore & Protect. The only issue there is that the 2026 model year Prius switched to 0W-8 and VRP doesn't come in that viscosity. They just started making it in 0W-16 about 6 months ago(I'm on my first oil change with it).

The eCVT transmission/transaxle is the most reliable unit on the market right now. Don't be scared by the CVT letters in the name; it's a completely different system than those. Fluid changes at 6y/60k is nice, but they're honestly pretty indestructible unless you're stupid or get into a bad accident. I bet you could go out to 9y/90k and the transmission would still outlast the rest of the car two or three times over.

The hybrid inverters have a bit of a potential weakness if you don't change the coolant on time. The pink coolant gets acidic over time, and it can start attacking the insides of the inverter if you let it go too long. Acidic coolant can also attack the head gasket coating, so it's just good practice to change it on time as well; 5y/50k for both. The inverter failures seem to start around 100k-150k miles, and usually in cars that never got coolant changes. Inverter failures aren't common or anything, but they do sometimes happen on higher mileage/older cars.

The HV battery should last the life of the car unless you let it overheat. In a HEV, that means keeping the airflow clear under the rear seat. In a current Prius PHEV, that means maintaining the car's A/C system. If you get an A/C fault, you HAVE to get it fixed right away. The car uses the A/C(technically a heat pump) to cool the HV battery. Without it, the battery might overheat and be damaged. It's also important to note that the car can continue to function fine as the battery degrades over the long term. You'll lose range 10 or 15 years out, but the car will still drive fine. I think the battery needs to drop well under 50% capacity before you'll start seeing fault codes. That's probably 15-20-25 years out.

You've seen others describe the issues with the 12V battery. I'm on my 3rd, but I live in a very nasty climate for them. The fan issue might or might not be linked to the refrigerant-cooled HV battery in the PHEV. It's possible the extra long tubing runs and all the extra o-rings might be increasing the likelihood of leaks. Toyota is using a completely different system on their new BEVs and the new RAV4 PHV, so maybe they acknowledge the problem(but there's no way to feasibly retrofit the Prius PHV without a complete(and extremely expensive) redesign). It might be enough for me to go with a regular HEV Prius or a C-HR or bZ, depending on my needs if I had to buy today. But YMMV.


Now for all the things you DON'T have to worry about:

No starter to go out
No alternator to fail
No belts at all to replace
No belt tensioners or idler pullies
No mechanical water pump
No power steering pump/lines/fluid
No A/C clutch to go out
No torque converter, clutch, clutch packs, or valve bodies to fail
Brake pads and rotors that often last 80k-200k miles(depending on driving habits)


Things you should do if buying new to give yourself the best chance:

First oil change at 700-1000 miles
Oil changes at 6m/5k after that (whichever comes first)
Always use quality oil(Toyota, Mobil 1, VRP, etc.), and Toyota filters are just fine
Always use a fresh oil drain plug gasket and never overtighten the drain bolt
Test brake fluid with a moisture tester about once a year
Change both coolants at 5y/50k
Change transaxle fluid at 6y/60k
Check engine air and cabin filters regularly and change when needed(interval is totally dependent on your driving conditions)
Keep a jump pack in your car just in case and know how to use it
Have your A/C system checked regularly(PHEV only) - Toyota says something like 10y/125k, but I might go way below that considering the reports from owners. But that's an expensive service because of the new refrigerant, so... (I'm just thankful I own a HEV for this one.)


I think that's most everything. Take everything I say with a big grain of salt and listen more to the professionals that actually know what they're talking about. Pretty much none of the active posters on here(including me) fall into that category. (though I know there are some real professionals that lurk from time to time)

Good luck on your decision and purchase.


Oh, and I'm at 3y/36k of ownership of my HEV AWD Limited. While I've put a lot of money into my car, it's all been voluntary. No problems besides recalls and the 12V battery. I am extremely happy with my car. The only things I wish it had were the auto heated/cooled seats and auto heated steering wheel that come on the new RAV4, dual climate zones would be nice, and I would kill for the truly integrated dash cam recorder that also comes in the new RAV4.

 

Nice writeup.
Heat pump for HVAC in phev?

 

In regular hybrid mode probably true, but if you're plug-in charging the battery, you can go something like 40 miles without using any gas.

 

it took about 10 years to recognize the weaknesses of gen 3. gen for has just gotten there and is looking pretty good. gen 5 has a ways to go, but I'd say so far, so good.
that's all we really know.

 

You mention TCO and thinking of purchasing a Prius PHEV.

Although the current Prius is a bit unproven, Toyota has an excellent reputation for reliability and a good warranty. Beyond reliability, key issues are your ability and cost of charging a PHEV and your typical driving patterns.

For me, the cost of electricity from 11pm to 7am is very low. And most of my driving is less than 80km (50 miles) per day at speeds under 80 km/hour. therefore, I run my Prius SE about 90% EV and I save significantly over a typical gasoline car. And for long road trips I have eliminated the range anxiety that comes with a pure EV. Also, there was a government incentive for my purchase that made it a “no brainer”.

If I had high cost electricity and lots of highway travel a hybrid or gasoline car would make more sense.

 

If that question is for me, I'm not sure I understand what you're asking.

 

A heat pump doesn't seem practical in a car to this layman.

 

Okay. I don't know your base knowledge in this subject, so I'm sorry if I'm telling you some stuff you already know. No offense intended.

And super sorry about the insane length of this post.



What is a heat pump?

Let's first define what a basic heat pump is. It's a collection of parts that includes refrigerant, a compressor, an expansion valve, a condenser coil, and an evaporator coil. It uses these parts to move(pump) heat from one area to another. Heat pumps that move heat in only one direction are extremely common. You already own several. Refrigerators, freezers, dehumidifiers, and air conditioners(both automotive and residential) are all examples of single direction heat pumps.

Now if you take a basic heat pump and add some bidirectional valves, you create a two-way or bidirectional heat pump. These heat pumps can move heat from inside to outside(cooling mode) as well as from outside to inside(heating mode). One of the benefits to this is that moving heat is many times more efficient than creating heat. That's why residential heat pumps can claim to be way over 100% efficient. They're being compared to furnaces that can only create heat. And it takes heat pumps far less energy to harvest 10k BTUs of heat from the outside air than it does for any electric, gas, or oil furnace to create 10k BTUs of "new" heat from a fuel source. And they're not even that much more complicated than a standard A/C unit. (They're also not new technology. My home has had a heat pump since it was built in 1978.)


Why heat pumps in cars:

So why go from a one-way heat pump(A/C) to a two-way heat pump in a car? In a straight ICE or normal hybrid, there's no reason. The best engines in cars today are around 40% efficient. The 60% remainder is waste heat. Since the engine is already producing vast amounts of waste heat, it's a no-brainer to harvest that waste heat and use it to warm the cabin. And that's what we've been doing for about the last century.

But what about PHEVs and BEVs? PHEVs spend long periods without running their engines, and BEVs don't even have engines to run. These cars need to need to heat their cabins somehow. They could use resistive heating elements(like space heaters), but those are insanely inefficient. BEVs that only use resistive heat for the cabin are why you see range figures drop by at least 40% in winter. The lost range is because the car is using significant amounts of electricity to heat the cabin instead of using it for propulsion.

I think you can see where this is going. All cars already have one-way heat pumps inside them. And heating via heat pump is many times more efficient than generating heat. So it's worth it in PHEVs and BEV's to add a little complexity to the A/C system to save significant amounts of range as temperatures fall. The limitations of heat pumps are that it gets harder and harder to collect enough heat from the outside air as ambient temps drop below freezing. Some residential heat pumps get around this by adding inverters or other tech. I honestly don't understand how these systems work, but they allow heat pumps to acceptably harvest heat down to -15F or even less in exchange for additional complexity and increased build costs. Since we're not seeing these types of heat pumps in cars yet(to my knowledge), I have to assume there are engineering or economic reasons preventing it for now.

In a PHEV like the Prius Prime/PHV, the car will use the heat pump down to around 30F. After that, the car will start the ICE and use its waste heat just like any other hybrid(with my climate, this is one of the reasons I chose to go with the HEV version of the Prius). In a BEV, the car will have backup resistive and/or infrared heating to take over from the heat pump as the temps drop below freezing.


What more does the heat pump in the Prius Prime/PHV do?

Since Toyota was already putting a full heat pump setup in the PHEV Prius for cabin heating, they also decided to use it to cool the HV battery. Toyota has been using air cooling for their HV batteries for 30 years, but the combination of lithium battery tech and the large capacities of batteries needed for PHEVs made air cooling inadequate. Adding a battery cooling loop to the heat pump probably seemed like a good idea. It's not like it's new tech or anything. But since new Toyota BEVs and PHEVs are no longer using it, I'm guessing Toyota has realized it's not as good of an idea as they thought. The current system Toyota is using on their BEVs and RAV4 PHEV is to use something closer to a geothermal/ground source heat pump as opposed to the far more common air-source heat pump.


What is Toyota now doing in their BEVs and the RAV4 PHEV and how does it work?

Back to simple stuff. In a residential/commercial ground-source heat pump, you use a liquid coolant(often propylene glycol) that flows through tubing in the ground. Then, instead of harvesting or dumping heat into the air, you harvest or dump heat into the coolant. Because liquids have massively higher heat storage potential compared to air, ground-source units can be even more efficient than air-source ones.

So what Toyota is doing now is connecting a refrigerant loop in the heat pump system to a refrigerant-to-liquid heat transfer unit. They then run a traditional liquid-to-air radiator on the front of the vehicle in place of the traditional A/C condenser coil in the case of a BEV, or they tie it into the HV inverter loop in the case of a PHEV.


Stay with me, we're getting there.

So let's look at the different parts of a BEV or PHEV that need heat and/or cooling:

Needs heating:
- HV battery (sometimes)
- cabin (sometimes)

Needs cooling:
- HV battery (sometimes)
- HV inverter
- cabin (sometimes)
- ICE (in PHEVs)
- drive motors (in BEVs potentially)

What Toyota's new* system does is actively harvest heat from systems that need to be cooled(like the HV inverter) and redirect that heat to the areas that need it. If no areas need it, or excess heat is being generated, they dump that heat into the liquid coolant and use the front-mounted radiator to dissipate it. If more heat is needed than the HV inverter and battery are providing, the system will try to harvest heat from the radiator. If that's still not enough, the system will use the ICE(PHEV) or resistive/IR heating to make up the difference. The heart of this system is a 5-way coolant valve in the engine bay. (Some Teslas actually use an 8-way valve, so Toyota's 5-way isn't especially exotic.)


This sounds complicated. How reliable is it all?

While it sounds complicated, it's really not. The core technology is actually really, really old. The real key to reliability is the quality of the materials used in the cooling loops. If the hoses are made of cheap rubber, the system won't stand the test of time. If the fittings and valves are made of cheap plastic, expect them to fail long before the life expectancy of the car. In a Tesla or Hyundai/Kia/Ioniq or BMW/VW/Merc, I'd be worried and would expect a high cost of ownership once these items start to fail and need to be replaced. But I'm hearing great things about the quality of the materials/components Toyota is currently using. I'm expecting the bZ, C-HR, Highlander EV, RZ, etc. to be bulletproof in terms of powertrain reliability and to have extremely low costs of ownership for the life of the vehicles. If Toyota made a hatchback, car-based BEV where the top trim had AWD and a 325+ mile range**, I'd be actively shopping to trade in my Prius(and I love my Prius).


Again, sorry about the length, but I wanted to cover most of the bases up front.



*not saying Toyota is doing something no one else is, just comparing it to the older systems they've used before
**because I take 100+ mile round trip drives in winters where the temps can be -20F or colder(where the heat pump has no chance of working), I need that extra range for safety's sake in case of getting stuck and needing heat while waiting for a tow

 

FWIW; you've got a 10 year/150K mile on the EV portion of the power train in a CARB state.

Op hasn't been back since posting.....