Ok, so it's not really KY and TN but that's what the gauge reminds me of. I can keep it out of far eastern TN in the panhandle area, the little pwr window, at least 99% of the time so ECO stays on. That's pretty easy to do. What's challenging is staying on the KY side of the line behind the picket fence rather than the solid white TN fence. I manage a fair amount of the time, not sure how much, but it's more of a challenge, especially holding that fine line of EV mode and maintaining a steady speed. It's fun trying it all though.
Ha, it took me a minute. You're describing the HSI as the shapes of Kentucky and Tennessee. The two places I visit most are western Kentucky (CHG through light EV) and western Tennessee through eastern Tennessee (engine cruising and accelerating). Central and eastern Kentucky (medium to high EV) put too much drain on the hybrid battery. This YouTube video is often posted on Prius Chat:
Yes, I don't have all the acronyms down yet and it just reminds me a little bit of those states. I'm mostly over in the ECO area but when I'm coming home the last 3 blocks are usually always EV plus a bit here and there the last couple of miles before that.
Yes, it's good to use ECO when you need the power, but you're right. Sometimes a little EV is all it takes.
EV can be practical if used correctly. However, there is NO free lunch in the EV driven Prius. The lower the battery gets the longer it will take for the regen or the ICE to fill it back up. Gliding is a little better alternative than straight EV driving. When done correctly, one can easily surpass the EPA ratings. If you try to EV all of the time, the battery pack just won't cut the mustard. It just isn't big enough. Unless you have a Plug In Prius, the energy must come from either regen or the ICE and the conversion process is not 100% either, so again you are still fighting a losing battle. If you are really interested in maximum MPG in your Prius, learn how to "Pulse & Glide". Then add to your bag of tricks along with air pressure settings in tires, keeping car aligned, along with maintenance of your vehicle.
When you're accelerating on level roads, I'd aim for half to 3/4's of the way on that bar graph: economical yet efficient. If you're starting off on a light-or-greater downhill, you maybe able to keep it below the median, avoid engine start up completely. On uphill starts, you'll likely encroach on the power zone, the only thing I'd say there is to definitely don't overshoot your target speed, and back off as you get close to that target.
