As an Espar owner (Hydronic 10), here a a couple of my thoughts:
1. They aren't all that reliable. Even the owner's manual says that if the unit doesn't start, to shut it down and try restarting it. I just don't know if I'd count on it to keep cats alive.
2. It's a significant project
to install one. We have four registers on our boat and I think I spent over 80 hours installing the whole thing. It called for 6AWG duplex wire to be run from the battery
to the boiler, for example.
3. The west coast
distributor for Espar heaters told me that I should not run it on diesel but rather on kerosene as, according to him, the diesel in the US is too dirty (not with actual dirt but it generates a lot of soot which can plug
up the units - it happened to ours). Apparently it's different in Europe
, where they're made and most common.
4. I spent almost twice as much on our Espar heater for our boat than I did for a furnace for our 2,000 square foot home. They're not cheap
Fair winds and calm seas.