We recently built a new 2 story home; 3700sf (my wife's idea; I would have been happy with a small A frame cabin). It's about 2000sf downstairs and the rest up. We ended up putting in a RSF Opel 2. I've gone two winters without turning on the heat pumps once. I'm in eastern Oklahoma, so not super cold winters, but we do have times when it runs 20-30s for a couple weeks at a time. The key to the Opel 2 is the ability to run a duct off the fireplace and blow heat up to 50 feet away (IIRC). I ran a duct into the upstairs TV room on the opposite end of the house that the fireplace is located (downstairs). I can keep the house a pretty constant 70-74 pretty easy. I don't think I could do that without the ducting ability. Not sure if your question if relating to a new construction home, but if so, I'd highly recommend a zero clearance fireplace that can be ducted. We couldn't be happier with ours.