On Thu, 06 Aug 2009 16:39:28 -0600, Robert Neville
wrote:

Oren wrote:

Not with gas units. They have a spark igniter - just like your gas
grill. Gas works when the power is out!

The flow of the water generates the spark? (I'm envisioning someone having to go
press the red button on thhe unit late at night!)

Don't hold my feet to the fire, but Bosch TWH indicates the spark
takes place after the hot water is requested from inside the house.

...hydro-generator..?

BTW TWHs can last many years and is easily serviced by the home owner.