In article , David Hansen wrote:
There is something to be said for a mini CHP installation burning
gas to produce electricity as well as hot water. However, if going
for that the heating system needs to be designed for it, not a bog
standard system installed by a plumber. Assuming a Stirling engine
the key is to ensure the unit runs for long periods, with long off
periods between, to maximise electricity generation. At least one of
the manufacturers recommends a thermal store.

I think that's probably equally applicable to fuel cell based mCHP
systems. Or will be, once/if household size ones reach production.
http://www.baxi-innotech.de/index.php?id=27&lang=1
http://www.cerespower.com/ProductOve...esidentialCHP/

(I have a thermal store, and a boiler I don't expect to last much longer....)