The amount of BTUs required for your home is dependent on several factors such as the climate in your area, and several features of your home including the size, the floor plan (single-storey or two-storey), the room layouts, the quality of insulation, the quantity of windows, and the location of the fireplace / stove. On average, 5000 BTUs can heat up approximately 450 square feet, depending on floor plan, windows, ceiling height, etc.
If you are deciding on the BTUs for your ethanol fireplace, please refer to this guide: What is the Largest Ethanol Fireplace for your Room?