The other night, I caught an episode of the Canadian CBC show, The Nature of Things, hosted by David Suzuki. The episode was called "Build Green" and was a fascinating tour through Canadian examples of single dwellings, buildings, and even whole communities, that are "green" and more self-sustaining. I highly recommend it if you can catch a re-broadcast. Definitely makes you wonder why this kind of planning/building isn't done more often.

Anyway, one example was a very small home--a micro-home, you might say. I believe it was off the grid. The architect/occupier of it showed the sleek, small power plant just outside the house, and described it as a Stirling engine, which he fed with biodiesel. He didn't mention the manufacturer, but after some digging around, I'm quite sure he had a model made by WhisperGen of New Zealand. From their website, it seems these engines may be used in various situations, both marine and terrestrial, on-grid and off-grid.

In this particular case, this single small Stirling engine produced all of the heating, hot water, and electricity for the house, combined with a small bank of batteries, along with some solar.

Anyway, my main question is, if anyone has any first hand experience, how quiet are Stirling engines? I have read in various places that Stirling engines are relatively quiet, but I have no idea what that means. The sound of a running generator could be a liability, whether during normal times in a dense urban neighborhood or when everything is very quiet, like during a power outage. Are they noticeably quieter than your typical portable genny?