Charge Mode ONLY mpg

As others have tried to communicate and have said, there is not an official average number when using charge mode. EPA doesn't require it, because it's not a "standard" mode. My assumption is that they test "as the car froms from the factory" to give the official milage. For example, the car is likely in Normal vs Eco or Performance driving mode.

There are significant effeiciency loses when burnging gasoline to charge the battery, just like the regneerative breaking doesn't give you 100% of the energy you used to accelerate the car.

If you search the forums here, you will see this issue has been discussed a number of times. People have given some estimates, but it is highly variable and no matter what, efficiency will be worse than not using charge mode. If you do some experiments, please report back, I'm curious too--but not curious enough to run my own experiments (e.g. "car sitting in the driveway in 50F weather, in charge mode, how much gasoline does it burn to go from hybrid mode to a full charge", or similar).

 

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Someone posted the driveway experiment thing to one of these Charge Mode or Prius Camping threads.
It wasn't pretty, but iirc it wasn't as bad as my example in #11

The other issue is that many Prime owners try charge mode once or twice without knowing anything about how it works, and seeing the MPG results declare it as a Useless feature and worse. And one of the threads got into a B mode discussion that lasted for 5 or 10 pages and seemed to never end even after a few tries were made to point it back towards a charge mode discussion.

I get kind of suspicious when I see a request for info and continuous complaints from the OP about the way others are responding to a post.

 

New 2020 prius prime owner here. I experimented briefly with charge mode as i am trying to figure out which driving settings yield me the best results. I would never consider running your car in the driveway to charge your battery. That is just a waist of gas. I have a oneway 30 mile commute mostly on the highway with various hills and cruise set to 65 mph. According to the car i got 44 mpg in charge mode on the way to work and was able to charge the battery fully (80%). On my return trip home i used EV mode and got 123 mpg (depleting the battery). I have more testing to do to see if it’s more efficient to drive in hybrid mode all the time or alternating between charge mode and EV mode. I suspect alternating between modes will be more efficient but am unsure until I do a full test starting with a full gas tank of each style of driving.

 

It's more efficient to let the car make those choices. I average 65+mpg on mine; so 44mpg really sucks and is 6-10mpg below the EPA sticker. If you really wanted to help efficiency; kill EV mode on the highway. MG2 is most efficient around 40-45 mph, not so much at 65mph - where gas/hybrid operations is more efficient. Switch back to EV mode on surface streets; off highway & stop-n-go traffic. There's also the question of what your paying for electricity vs gasoline. My electric bill went up by $25 a month, but my gas bill went down $65 month when compared to my old PriusC; over the same commute. You can only imagine the savings going from a full ICE to a gen4 prime.

Hope this helps.....