Plugin hybrids have the worst of both options as well as the best.
They have to carry with them an entire gas engine, plus large electric motors, plus a huge battery. That's a lot of mass. This makes them inefficient as gas vehicles, and less efficient as EVs.
Take a look at the Toyota Prius Prime, considered a great PHEV. It's got almost the same gas milage in combined city/highway driving as my 2012 Honda Civic (around 50 mpg). The Prius has got a slight edge. But that's combined, which presumes 45% highway and 55% city. You don't want to take that car on a road trip because once the battery is dead, you'll be needing to stop to refill the gas tank every 90 minutes. My Civic will drive 600km or more on highways, easily.
PHEVs are the best vehicle if you drive less than 60km per day, and mostly have stop-go city driving (so you can recharge on braking).
I'm a bit confused by your numbers, and I suspect we may be mixing multiple units of measure (maybe due to different definitions of gallon?).
The 2021 Prius Prime is rated at 53mpg highway. Let's assume that is optimistic and it gets 50mpg. Its fuel tank holds 11.4 gallons, but you don't want to run it dry - let's say 10 gallons are usable. That is a 500-mile (~800km) range after the battery is dead. At 75mph, that requires stopping to refill the gas tank every 6 hours and 40 minutes.
The most efficient 2012 Honda Civic is the hybrid, which is EPA rated at 44mpg highway. That is very efficient. However, 44mpg -> 53mpg is a 20% increase in distance per gallon of fuel. The Prius Prime is significantly more efficient. Since we're intentionally ignoring electric range in these numbers, I think the efficiency gains are mostly from the 9 years of R&D that passed between these two cars being built.
Interestingly, the non-plugin 2021 Prius Eco is also rated at 53mpg highway. I do think it's odd that the extra weight from a larger battery didn't have a bigger impact on fuel economy. It looks like that makes a small difference in town, where the Prius Eco gets 58mpg vs the Prius Prime's 55mpg.
The new Prius is probably larger & faster and meets more safety & emissions standards as well.
And it will get much better fuel economy than the Civic as soon as traffic gets bad or some city driving is required.
Picking highway MPG cherry picks the solution that makes the Hybrid or EV look the worst compared to the traditional ICE car.
Not that the Civic is/was a bad car. But all cars are a lot bigger and safer than they were, so it's almost always cherry picking to go back and take an example of an old fuel efficient car. A lot of those old cars could not pass modern emissions or safety testing, they got their good fuel economy by being a) Slow b) Light. A big part of light was not having extra mass for safety or emissions. On top of all that the mileage ratings for cars have also changed, so you can't even directly compare the ratings for an old civic with a new one.
To be fair, the EPA changed the way they calculate mileage ratings in 2006 (affecting window stickers in 2008), so the 2012 Civic is a valid-ish comparison. Also, I chose the most efficient Civic available, which was the hybrid model.
I do wholeheartedly agree with you, though. Even when cherry picking data (highway mpg's, ignoring miles driven in EV mode, choosing the most efficient Civic) and ignoring other factors (larger, safer, lower emissions), the Prius Prime is much more efficient. I think plugin hybrids have their place.
I'm gonna to be blunt: after reading more reviews, I picked a very poor car to use as my example of a bad PHEV. Prius prime actually sounds like a pretty solid vehicle.
The general complaint that I hear about other PHEVs is that car manufacturers publish the "combined highway/ city" rating, which is weighted heavily in favor of city driving- which is where a PHEV is incredible thanks to regenerative braking.
But if you're not using the brakes and just driving a long distance, your battery stops helping after 30-ish minutes and now you're just in a gas car with an undersized engine carrying a very heavy battery.
Better to go pure EV instead, which is what I'm on a damned long waiting list to do right now.
I really think you should test drive one. It doesn't have a huge battery and ice engine, it has a small battery and a small engine (at times frustratingly underpowered if out of battery). For short drives, the small battery saves you from hauling an extra 500 lbs of battery. For long drives a PHEV is still my preferred option over a BEV, because refueling every 300 miles is faster than recharging every 300 miles, and I'm not looking to have a spirited drive anyway.
Weight is not that important for highway driving especially, where the vast majority of resistance comes from air and not rolling resistance. It’s mostly bad for ICE stop and go, where you have to get the whole car moving again from a dead stop repeatedly.
> you'll be needing to stop to refill the gas tank every 90 minutes
This is just wrong. The Prius Prime has an 11.4 gal tank and is rated 53mpg on the highway [1]. If you drive 70mph you'll need to refill after 7+ hours of driving and 500+mi.
I have a Chevy Volt, with smaller gas tank size (9 gal) and highway fuel economy (40mpg highway real-world). I fill gas every 6 hours of highway driving after the battery dies.
> PHEVs are the best vehicle if you drive less than 60km per day, and mostly have stop-go city driving (so you can recharge on braking).
Nit: it's the low average speed of stop-go driving (less air resistance) that makes city driving more efficient for EVs. You'd get even better efficiency for the same average speed if it weren't stop-go driving.
They have to carry with them an entire gas engine, plus large electric motors, plus a huge battery. That's a lot of mass. This makes them inefficient as gas vehicles, and less efficient as EVs.
Take a look at the Toyota Prius Prime, considered a great PHEV. It's got almost the same gas milage in combined city/highway driving as my 2012 Honda Civic (around 50 mpg). The Prius has got a slight edge. But that's combined, which presumes 45% highway and 55% city. You don't want to take that car on a road trip because once the battery is dead, you'll be needing to stop to refill the gas tank every 90 minutes. My Civic will drive 600km or more on highways, easily.
PHEVs are the best vehicle if you drive less than 60km per day, and mostly have stop-go city driving (so you can recharge on braking).