The warmth of an open fire resonates deeply in our species, but 90% of the fire heat goes up the chimney and much of the heat in the room goes, too. If you generated that heat with another system, you’re wasting twice as much fuel.
You might consider a fireplace insert instead. Alternately, you can place a wood stove in front of your fireplace. Small Farmer’s Journal has an article on how to do just that.
For more, check out this EPA deep dive into fireplaces and fireplace inserts.
The two variables of of heat loss are a) geographic location, and b) building performance. Together they will determine the quantity of heat needed to maintain comfort.
Geographic location drives the building's “design day." Your design day is the difference in temperature between the inside and outside of your house on the theoretical coldest day of the year; so in the northeast we calculate a day that is -10ºf outside and comfortable 68ºf inside. This is referred to as the “delta-T” value. A typical delta-T for the northeast is 78º.
Building performance is the big one because there’s nothing we can do about geographic location. Today we can build a really tight thermal envelope, but most of our heating pollution comes from the millions of homes built over the last 100-150 years. We are getting better at buttoning-up those old buildings with insulation and weather sealing but weatherization is still never going to be enough to overcome the heat loss from a 78º delta-T. That means we need heating systems that can quickly put a whole lot of heat back into those old houses on the days that are really cold.