General priciples discussed a while back here
https://groups.google.com/forum/?hl=...-y/7W2oLZE-rII

People are looking at this the wrong way around. It's an electricity
generator first and foremost. The Carnot Cycle means that rather more
than half the energy used will be waste heat that is just dumped at the
power station or used to heat the nearest greenhouses. With this
mini-CHP, that waste heat will be used to heat your home. That's the
theory, anyway.