It might be different where you live, but where I've lived, most gas-burning fireplaces are only for ambiance...they never seem to make much heat, just a pretty flame. Consider this - gas is one of those commodities whose price fluctuates up and...up. Doesn't really ever go down. With wood, you can get creative about where you get it. We frequtnly get a cord of wood in exchange for helping our friends clear off a hunk of their land. A days' work seems to be equal to a cord of wood, or at least a pickup truck full (half a cord). We have a free-standing wood-burning stove, and it provides a LOT more heat than the fireplace that we replaced with it. The fireplace has fans that re-direct air from around it. With those fans not going, it produced effectively zero heat - caused more cold air to come in the house than hot air that it produced. With the fans going, it would warm the room it's in, but required at least twice the wood as the free-standing stove. If the power went out, we could not use the fans, and the fireplace was warm only if we sat right next to it. We got a stove with a glass window in the door, and we like the ambiance just fine, about as good as the fireplace was. We live in timber country and have a good supply of firewood, so that certainly biases our decision. We get a lot of power outages, and now that we can heat completely with wood, we're feeling a lot less vulnerable. Our last power outage was long enough for the house to get down to 43 degrees (all-electric furnace; no natural gas available here). A bonus for us, in this small house, is that the wood-burning stove, even with the required masonry pad, takes up less room than the fireplace, which we now plan to remove, along with the wall in which it sits. Which is better for you will vary by what's important to you. But for most, the free-standing stove is the most efficient heater, and using wood as a fuel is better for disconnecting you from the grid - making you less vulnerable to the ever-increasing prices of fossil fuels. You already know the big downside of wood - it takes work to chop, split, haul, and then tend the fire.

I would ask the gas fireplace manufacturer and/or the heat pump manufacturer or installer.

Thanks, Will. Ten degrees several times during the winter sounds about right. Sometimes I forget just how cold it gets here. We are in the city itself. I keep the thermostat around 68 degrees. On a cold day outside when it's 68 in the front of the house, it's about 63 in the back (ie, the new addition). Thank you for framing it in terms of heat deficit vs. distribution. The ducts are basically vented to the front half of the house; partly because two were taken offline in the process of building the addition. And partly because it's awkward to run them to the furthest part of the new addition without getting in the way. (Thus the reason why we're in this predicament of considering a fireplace). We had a blower door test done - house is circulating 30% of its air each hour. And we did have a heat load calculation done - that's how we arrived at the 75K figure. But it would be great if the current furnace could handle the whole load. So all of this is to say, I'm still curious to know what size fireplace we might install. I'm guessing it wouldn't have to be very big. Anyone want to estimate what we would need?

If you are seeking a free-standing gas stove, Woodstock has a very attractive 17-inch stove that can be wall-mounted. It is perfect for a room no larger than 600 sq. feet, e.g. a den, bathroom, or perhaps a boat or mobile home. Be sure to vent it correctly. Here is a link that might be useful: Woodstock small gas stove