On Sat, 6 May 2017 19:28:12 -0000 (UTC),
(Andrew Gabriel) wrote:

It was done - Whispergen and another I forget made domestic boilers
with 1kW electricity output. They weren't viable and the companies
abandoned the domestic products when the development subsidies were
withdrawn.

Sounds about right, one was a free running piston and the other used
three cylinders and a swash plate IIRC

AJH