Welcome to the forum.
I looked at the Jayco online brochure and I couldn't tell from that if the HWH has electrical heating elements or not.
As far as I know, HWH with electrical elements have a switch to turn electrical heating off and on, not automatically switch between electric and propane.
Sherm & Terry w/rescues Steve (std Poodle) & Eydie (min Schnauzer)
2015 Jay Flight 27RLS (Camped: 102 nights 2015, 90 nights 2016)
2006 Ford F350 6.0 PSD, Lariat, 4WD, CC, LB, SRW, auto., Camper pkg.