The Leaf to Home power station in the above photo Plugs into the CHAdeMO port. The power take-off device(PTD) on the Mirai is a CHAdeMO port in the trunk. I'm guessing CHAdeMO was selected over the AC charge recepticle because the power station is a more efficient inverter than the onboard charger, and/or it has less restrictions on the amount of current being drawn from the car to the house. As for the Prime using CHAdeMO using this, it was mentioned in the Japan event thread as one of the reasons that North America won't see the home power option.
They do in Japan, there was a request here to expand it to other territories, perfectly logical don't you think?
So did my 2004 Matrix, but for whatever reason, Toyota isn't offering this on Prius Primes outside of Japan, and neither did they on exported PiPs. For those that want to be able to use their Prime for emergency power, what Toyota offers on the car outside their market doesn't help them. Until Toyota offers the AC outlet outside Japan, these people are stuck with installing an inverter themselves as the only option.
By the way, it would be helpful to find out the 12V sustained amperage rating of the G4 and of the Prime. It is 100A on my G2.
Off topic but interesting: The label on the flip cover of the charge inlets in Japan shows AC 100V/200V and 15A/20A which are probably the ratings of the onboard charger? Also shows DC 400V. See post #15 here.
Yeah, would be handy to be able to buy one of these power out adapters with U.S. specs. Here's more on it from Toyota's japanese page (in Japanese, can run through a translation filter): トヨタ プリウスPHV | キャンペーン | 電源供給サイト | トヨタ自動車WEBサイト
Option for the charger timer to stop charging at ~80% of full (say, 20 miles). Could be useful for those who are living on top of a hill. OK, I know, 80% may not be sufficient to some but 80% for 80% is also something.