What would really be useful, if they had "zoned" heating. You could set main cabin "zone" to desired temperature and basement/belly "zone" to 38-40°. That way when you're running electric heater and tank area, gets cold, furnace kicks on, until that zone is satisfied.
I run electric wall heater off, thermostat set at desired temperature and furnace set couple degrees cooler. When I have power, electric heater, takes care of it, until about 28° outside temp and then furnace kicks on. This has been working to keep tanks plumbing warm enough. I tested it last year, down to single digits, (thanks Texas) with 1,000watt floor heater. This year, I upgraded to "cadet" 1,500watt wall furnace. I'm not sure, if more powerful heater, will allow furnace to run often enough. Hopefully I don't run into single digits, this year, to find out.