We switched from an electric to propane water heater 5 years ago mostly for
comfort during power outages. Propane cost has gone up so much - over
$2/gal while electricity is still $.06/kwh. Now we could save 20% going
back to electric. Even if it would never pay back, I still like the idea of
not emptying the propane tank so quickly.
I am thinking of installing a medium size tankless electric water heater
in-line ahead of the propane water heater. It would shift about half the
energy use to electric while preserving the 40 gallon reservoir. Maybe a 40
amp 240V unit, something like 1 gpm at 70F rise or 1.5 gpm at 45F rise.
What's good or bad about doing this? Is it OK to preheat the water into any
old propane water heater? Do I need to look hard for a tankless unit that
has no flow restriction, since I'd still want the full flow through the