An electric fireplace? With a 1500w heater? That isn't going to last long on two batteries unless they are huge like 4 or 8-D's. I would suggest replacing the bulb in it with a LED and using the furnace for heat. It will use a fraction of what a 1500w heater will.
Last year we had 490w of solar and 345 Ah of battery and could do pretty much anything but run the air conditioner. This year we wil have 750w of solar and 675 Ah of battery and will be able to even more electrically including running a small window air conditioner and even cook with electric when the sun shines.
So you can set up a system do do just about anything but you have to know what kind of power you need, have the battery to hold it and the solar to replace it. You may have more room on the roof and definitely more storage than I do in my trailer. Set up a system that meets your needs.