Battery only

Unless you install the EV button, it won't really be up to you whether the gas kicks in. The car decides when to run on electric only, etc, and will automatically kick in the gas engine if your battery is low and needs recharging. There are ways to alter your driving style to try to convince the car to go into a certain mode (ie, go into electric only a little earlier than it would have by itself or so that there is no energy flow to or from battery), but you really don't have to worry about monitoring the battery and altering your driving conditions to charge the battery. You really can just drive the car. Hope this makes sense/helps.

 

As betshsu said, just drive it The MAX in EV only is 42 mph, but that doesn't mean that it will use EV only until the battery goes too low, then kick the engine on. Even very slight upgrades will kick the engine on. It is nearly impossible to leave a stop or traffic light on EV only unless you accelerate VERY slowly and there isn't anyone behind you. You might actually start looking for the lane with the heavily loaded semi to get behind. People don't get POed when they don't do 0-40 in 4 seconds.

Unless you have another almost immediate stop, inching up on EV will only use a larger percentage of the battery potential to do the hard work - getting the mass up to speed, leaving the engine to do the easy part - keeping it at speed, while it recharges the battery.

You'll find that if you can keep a fairly constant speed ie. not many traffic controls or you can leave enough gap that you limit your stops, and the terrain is fairly level, the car, once warmed up, will pop in and out of EV (use the cruise control) all by itself. As betshsu also said, you can also learn to encourage it but you really can't force it to stay there if it doesn't want to.

 

Hm, I don't think not driving over 40 mph will wear on the battery any more than any other type of driving. You're not going to be spending all your time in EV mode, even if you don't drive very fast. The majority of my driving is very similar to yours (local driving, usually not going faster than 45 mph, slight uphills and downhills) and I spend some portions of my drive in EV only but never the entire drive.

 

I'll guess that you will see really good gas mileage with your Prius, 30 miles under 40-45 miles an hour is what the car is designed for to get the best mileage. Wish my commute was around 40 miles an hour, I'd probably make 60 miles to the gallon.

 

my best mileage comes from that low speed driving too, but its difficult to maintain since every stop robs you of momentum that is needed to maintain the high mpgs.

i find that my best mileage with any consistancy comes when on country roads with minimal stops that are usually at 50 mph. ive frequently done stretches of 40-50 miles at 70+mpg in the summer.

also realize that even at 30 mph, you might be in EV mode maybe 90-100% of the time but the ICE will still run 25-35% of the time too. the reason for the more than 100% totals is the biggest reason why the Prius is so well designed.

the car does the thinking for you. you just drive. for max efficiency, it is NOT better to run the EV at constant speeds of 35-40 mph. you will get higher mileage overall by running the ICE. what kills the mileage is accelerating. you will find that while maintaining speeds, the ICE alone is capable of getting GREAT mileage.