Hi Dan-O
I was heating my hotwater today with 107 watts of solar PV power..
But, not by choice..
Within a week, I hope to be heating with a full 500 watts of PV.. (1,706 BTUh).
Solar Tracker Project - Page 7 - EcoRenovator
That 107w ~ 367 BTUh might have made up for some of the losses,
because my oil burner hasn't come on today (yet)..
Good luck with your gas bill..