What do the "power settings" actually do?

I have a 2017 Prius 4. The different modes just change timings and throttle sensitivity. Power usually kicks the ICE on earlier in the pedal travel. There isn't "extra power" to be had or a sudden increase in acceleration or top speed. I have mine in Power mode all the time. Less pedal mashing to try to accelerate. If I was in ECO I would need to put the pedal to the floor before the Prius knows that it should haul nice person vs say half to 3/4 of the pedal travel in Power. I'm still getting 50mpg. Even though I'm in Power mode, I can be light enough on the throttle that it can still feel like ECO. I've also been able to keep it in EV mode from stop to 50mph by being very light on the throttle in Power mode.

 

In the USA: I can definitely tell you that ICE will not start unless it is below 32 degrees (I believe, I live in Florida and noticed this on vacation in 20 degree temps) unless you are demanding heat with the climate system. I have to hit my climate control off or drop down the temp right when I fire up my car. IE I have AC set at 71 and outside is at 70, it will fire the ICE when engine is cold. I have a decent sized parking lot and the engine will not start then until either going over 20 MPH, battery falls down to two bars, or I hit the pedal too hard.

 

I only use the power setting. My avg so far after getting the car in Dec is 5.8lt/100km. I drive it like I drove my Rav...not pussy footing it around. It's actually pretty quick up to about 60km/hr.

When the warmer months hit I can see that avg dropping.