My 2026 Plugin Prius Buyers Regret...

I don't think the Prius transaxle can actually do that- that is, generate enough power to significantly charge the PHEV battery while also driving at highway speed and holding the gas engine to a low RPM all at the same time.

Engine noise during acceleration and hill climbing was always part of the Prius experience. I don't think I would have expected that to go away when they added part-time EV capability to the PHEV model.

Though, I can see where it's a sharper contrast in sound when the PHEV model allows more of your total driving to be done in the quiet EV mode.

Also there's a bit of a "well there's your problem" statement to be made if you aren't regularly plugging the thing in- I don't mean that to be a cheap shot gotcha. But if you paid for that capability, why not take advantage of it?

 

At highway cruise speed, the constantly-running engine is in its efficiency zone - doing more work to fill the battery to use the charge later is a net loss - charge/discharge losses mean you're burning more fuel to fill the battery than it would have cost you to use hybrid mode later.

Battery filling by choice only makes sense efficiency-wise when you would otherwise be running the engine significantly below peak efficiency, so the efficiency gain from taking more engine power outweighs electric charge/discharge losses. .

At low speed, a constantly-running low-loaded engine would be inefficient, so it does make sense to alternate between charging the battery and stopping the engine and using charge - that's the standard hybrid operation.

The speeds where OP would like to use EV are the speeds where you could be slowly building up charge efficiently. With a bigger battery you could run the standard hybrid algorithm on a bigger timescale - rather than alternating once or twice a minute while in town, you could alternate every few hours of driving. But it still wouldn't make sense (efficiency-wise) to fill it up while highway cruising.

So the car doesn't do what OP wants - the aim is to be an efficient hybrid with plug-in ability, not a fuel-powered EV.

New regulations are the reason the Charge mode button went away in America - new CARB rules required that emission measurements are done in the most polluting user-selectable drive mode, which would have meant testing in Charge mode. Charge mode remains available outside North America.

So elsewhere you do retain the option to spend fuel now to avoid running the engine later, but it's not generally the smartest thing to do - if you want to run EV later, you should have filled from wall charge, and be running hybrid now to save charge to run EV later.

 

I get some of the reason they got rid of Charge mode, but I was also mad when I noticed the feature gone. 1) I dont think there would have been much of a EPA change from 2025 to 2026. Hell under the new admin they have been cutting back on allot of the bs letting Dodge and others bring back more v8s. 2) Then you find out that Parts of Canada and Europe that have higher restrictions get that option even on 2026s which rub it in more.lol. Which also adds in the oil type difference between here and there. I have been unable to find out the exact change if its just a switch change or if there is a switch and software change and if that can be put back with Toyota tools. Service people and the main Toyota call centers dont seem to know chit. Hell the lady just read stuff off without really understanding what chg mode was. lol I understand its something that shouldn't be used much, but if others have it I feel cheated. Either way I love the car.. I just have to tuck my head down more getting in.

----The 2025 (formerly known as the Prius Prime) features distinct EPA ratings depending on the trim level, with the base SE model offering superior efficiency and range compared to the heavier XSE trims.

• SE Trim: Rated for 44 miles of all-electric range, 52 MPG combined fuel economy, and 127 MPGe (miles per gallon gasoline equivalent) when operating in combined electric/hybrid mode.
  
  
• XSE and XSE Premium Trims: Rated for 39–40 miles of all-electric range, 48 MPG combined fuel economy, and 114 MPGe
  

---The 2026 Toyota Prius Plug-in Hybrid features EPA ratings that vary by trim level, with the base SE trim offering the highest efficiency and range.

• Electric Range: The SE trim provides an EPA-estimated 44 miles of all-electric range, while the XSE, XSE Premium, and Nightshade Edition trims are rated for 39 miles.
  
  
• MPGe: The SE trim achieves 127 combined MPGe, whereas the higher trims earn 114 combined MPGe
  

 

I didn't say EPA, I said CARB.

The new rules for 2026 added this:

 

I don't really care because I don't own a Prime/PHV(and wouldn't use charge mode even if I did), but the modifier in me is 99.9% certain you could add the charge button to new models that don't have them if you really, really wanted to. The annoying part would be adding the wiring from the center console to the Main Body ECU and/or the Hybrid ECU.

If the Prius PHV still has charge mode in Europe(and Japan?), that means the ECUs still have the programming. You just need to add the switch. Buy a new one from Toyota or a used one from a wrecked 2023-25 Prime. Look up the wiring diagram for a 23-25 or any EU PHV and run the switch wiring to wherever it says. Boom, charge mode added.

 

But it's not a separate switch, like the American Gen 2's omitted EV mode.

You enter charge mode by long press of the HV/EV button. The button hasn't disappeared, just the "HOLD CHG" marker.

I think that means it's almost certainly an ECU change, unless it's a very advanced button sending press length over some sort of network protocol.

 

Sounded like an advanced button from some sources on the subject.

If it is just a change in the ECU software, an interested tuner with figure out how to flip the 'switch'. It has happened in Sonics for E85 and flexfuel use; older GMs with Holden roots for lean burn mode, and the CARB hobbling in i3 RExs.

 

The CHG mode is handy for certain conditions. I have used it to build up a charge on a road trip for car camping. It will charge the battery to just over 40 miles of EV range which is usually enough to run the climate control overnight. I have also used it when I have a long wait for a ferry coming up so that I can sit in the car without the engine coming on.

I have checked it on long trips to run EV in city and HV/CHG on the highway and it does seem to be quite efficient and not much different than HV mode.

Hopefully you'll find a way to enable it.

 

Ahh. I thought it was a separate button. My bad.

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(does research this time)
...

So it's not a separate button in any sense of the word. The whole parking brake switch assembly is one unit.

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(plummets down the rabbit hole and pays for access to US and EU tech sites)
...

Still can't give a solid answer.

Things I know:
1. No wiring changes from 2025 to 2026
2. There is only one wire involved (labeled EVHV)
3. The hybrid ECU changed part numbers from MY25 to MY26
4. US MY26(w/o charge mode) and EU MY26(w/ charge mode) still use the same hybrid ECU (so the change isn't hardwired in the ECU)
5. The switch assembly has a new part number (but that could be just because of the printing on the switch)
6. The new version of the switch assembly is 13% cheaper than the old version

So there are two scenarios:
1. The change is software-based and done when the hybrid ECU is initially programmed(why US and EU ECU's are still the same)
2. The old switch is different internally and sends a special signal when it's been pressed and held


It will cost someone with a 2026 US PHEV about $110 to test. They'd have to buy the old version of the switch assembly and see what happens. The install is fairly easy. The piano black portion of the center console needs to be popped up to access the four 10mm or philips screws that hold the switch assembly to the trim from below. With a small ratchet or stubby screwdriver, a person might not even have to fully remove the trim section(it includes the cup holders and storage tray). Four screws and one electrical connector and the job's done. Maybe 5-10min for a trained tech; 15-30min for a novice. For testing purposes, a person wouldn't even have to remove the old switch; just pull up the trim enough to unplug the old one and temporarily plug in the new.

These are the three versions of the switch assembly:
84390-47110 - HEV, 2023-onward
84390-47110 - PHEV, 2023-2025 US, 2023-onward EU (w/ charge labeling) - $215.55 MSRP, $149.03 today, $111.78 during 25%-off sale
84390-47140 - PHEV, 2026-onward US (w/o charge labeling)


I'm going to guess 60/40 nothing happens if a 2026 owner swaps to the older switch. I lean toward KMO being correct and the change is in the ECU programming. But the drop in the switch price and the fact that the US and EU hybrid ECUs are still the same part number means a physical change to the switch is still in play.

Besides a '26 owner buying(or borrowing) an old switch to test, another way to know for certain would be to attach an oscilloscope or other advanced reader to the wire* on a 2023-25 PHEV model(while everything's plugged in and the car's running) and see if there's a signal difference when the button is held for the needed amount of time. Does the button send two distinctly different signals, or is it just a single continuous signal for as long as the button is pressed?

But I don't have the tools or the car to do the testing, so that will be up to one of you guys if you really want to know.


*probably pin 6(blue - EVHV), but possibly pin 3(gray - EVMS - EV Mode Select)