People always ask "If a Prius is electric, then where's the power cord?", and you have to patiently explain that you don't plug it in because it generates its own. Now here's one that you do plug in. Huh?
Normally a Prius harvests electricity when its engine has power to waste, or when it's coasting. That electricity is used to help the engine when it needs it, or even to push the car along engine-free for up to a couple of miles. The Plug-in Hybrid Vehicle (PHV) version has a bigger battery, which you can charge from the mains. This gives about 12 miles of gentle electric-only driving.
Hmmm: 12 miles. If you knew your car had just a litre or two of fuel left in the tank, you'd probably just drive around looking for a petrol station. By the same token, isn't a 12-mile electric range a bit pointless?
No. Because this isn't just a plug-in vehicle, it's also a Prius. So you don't need to worry about running out of electrons, because when that happens the engine starts up and it behaves like an ordinary Prius. Same performance and economy. When commuting trips and errands are less than 12 miles, it can ‘graze' electricity at the end of each small journey - home, office, electrified parking meter. Especially because 12 miles-worth of electricity is less than most EVs, it'll charge in an hour and three-quarters.
The Prius PHV actually uses the same electric motor and petrol engine as a normal Prius. But it runs a higher voltage, so the motor makes more power. The rest of the electronics are uprated to suit, and the battery is a lithium ion one. It sits under the boot floor as usual, but is bigger, so the floor's a few inches higher. No big loss.
Even so, the Prius PHV's electric motor only makes 50kW- that's 67bhp. That's a lot less than a Tesla or a Chevy Volt. Accelerating flat-out in electric mode, you'd have a pretty hard time seeing off a double-decker bus, and top speed is only about 60mph. But it doesn't matter, because even in electric mode, if you floor it, the petrol engine cuts seamlessly in, and off you go just like in a normal Prius.
If you find a socket, any journey under 12 miles becomes almost free since electricity is so cheap. And because the battery is so much smaller than in a Tesla or a Volt, it won't cost as much to buy either. Though we don't know how much less, because so far Toyota is still at the experimental lease stage.