Every persons reply got me on the right track. Geosierri, I think the heater you use is also used for heating soil under a planter to start plants. Where I found it. I saw a review on amazon where a person said it scorched his pillow and melted. I lkied the idea of using one but saw a different brand I liked  All the ones I saw used 120vac.which I will have from grid power.   Horse fly, I looked at your honey bee heater. I kind of think I might go with that but might need a converter to get 12 vdc. I just ordered a new 48 volt inverter today but do not know if there is any 12vdc output or not. Also I have another 24 vdc inverter system. I plan on dedicating to my water pump where the inverter will be in sleep mode till pump needs power. I am going to use my off grid power to run 2 ductless heat pumps and my water pump.  I will be working this spring to get it all running. I started it last summer and got the covid and was on oxygen for 3 months. So I will finish it this year.  PS I was also thinking of using an electric heat tape that is used to keep waterpipes from freezing. I think it comes on at 38 degrees and off about 42 degrees or something like that. I used it on a chicken water tank and it never froze. 

I guess I need to explain my system a little better. I am grid tied and plan to run a 240  vac line from house to my solar shed.  I have an old 24 vdc fork truck battery about 12 years old and just want to dedicate it to my deep well pump with a trace inverter and  and auto transformer  that I have. . IT will be in sleep mode most of the time. I bought a 48 vdc growatt inverter To connect to the 9 solar panels I already have so I can power a bosch 18,000 btu  mini split heat  pump To heat and air condition my house. Going to buy a couple of those rack mount lipo 4 batterys from Signature solar.com. Originally I bought 9 solorworld 290 watt solar panels and was going to have a 24 volt system with a midnight solor charge controler but decided to go with the growatt inverter. What I like about it is it also has a 100 amp charge controler and has a ac battery charger and can get power from the grid to add to the load to run the minisplit. That wayI don,t have to bother with a transfer switch. If I have too many low power days I still have the propane for a backup. When the gaswell that I had quit around thanks giving It cost me about $,4,000 dollars to get a used 500 gal tank and 400 gallons of fuel. I decided to go the mini split route when I was told that it is cheaper to heat than propane. My daughter had her 500 gal tank filled a couple weeks ago and it cost over $1,000.00 to get her tank filled and her tank is the same size as mine. For people that don,t know you only fill a propane tank 80% and have to leave the other 20% for expansion when the sun heats up the tank.