First, let's remember that with a reasonably sized engine at cruising power, there is not much to be recovered by an exhaust turbo, without paying for it in back pressure. However, for an optimised setup operating near full throttle, the Napier Nomad turbo-compound engine hit the magic 50% efficiency forty years before the turbo-charged ship diesels managed it.
Napier Nomad - Wikipedia, the free encyclopedia So, if you want to spend a few thousand bucks on a ten-hp. generator for your hybrid, there are fuel savings to be had, assuming that turbos can be scaled down without loosing too much to the square-cube law.