Wired writing about my Mazda:
You can’t sneak off to the bathroom at its Hiroshima plant without someone reminding you the rotary is a part of their DNA.
And later:
Even if you run it on gas instead of hydrogen, a rotary is better suited to being a range extender than a conventional engine. That’s because it’s especially efficient at low, constant engine speed (rpms)—which is exactly how a generator runs. Its compact size helps, too.