Yeah, they also live in Australia where it's likely that with their climate water is going to heat much faster anyways. How many rocket water heaters have you built or had direct experience with (particularly in cold climates)? I am eager to construct one within in the next year here in zone 5 Michigan.
So you are the Ernie in Paul's videos I assume? I have some questions about the greenhouse you were building with the rocket mass heater in the bed... Will one fire create enough heat to keep the ambient temperature in the bed above, say, 40 degrees Fahrenheit through a night in the middle of a zone 5/6 winter? I'm really intrigued by that design and want to learn more about what sort of advantages it has on season extension.