Yes, I could put a lot of coal in my 118 when it's finished, but that roasting pan with a 20 pound turkey in it just won't fit through the loading door !
And yes, the kitchen ranges are not meant to run as long as the Oaks and box stoves, but for sake of discussion of stove designs as heaters and their efficiency, I snuck it in.
My kitchen range won't hold near as much coal as an Oak - only about 25 pounds of nut (one #16 coal scuttle full) fills the fire box. At usual settings for our cooking temps, it will go about 4-5 hours before needing a good shake-down and reload. But, damped down like I do for "night mode" when it's just being used as a heater, it doesn't run much cooler, and it will consistently go 11 - 12 hours - unattended- on that 25 pounds.
When I come downstairs in the morning, my un-insulated, large kitchen, which has 9 foot ceilings and tall windows (oh, those crazy Victorians), stays at 65 degrees, . . even when outside temps are down below zero. The left end area of the stove top stays at least into the upper 500 degree range, more often into the low 600 degrees. At 30 inches above the stove top (just below the stack damper) the pipe is down in the low 100 degree range. Most mornings you can keep your hand on the pipe. And it may run a bit longer than that once the old girl is rebuilt and properly sealed.
So, for the sake of discussing efficiency (heat output per Lb of coal), if we can extrapolate a bit, . . if I could fit 50-60 pounds of coal in that same kitchen range, I think it'd very likely run as long - maybe even longer then a base heater.
I know that my Oak, even with the indirect back pipe added, has a lot less surface area to extract and radiate heat than my kitchen range. And, with an 18 inch fire pot, my Oak is one of the bigger ones of it's type, while my kitchen range is one of the smaller. However, small as it is, it has 8 feet of flues inside it when it's in indirect mode (oven on), with a lot more outside surface area to shed that heat before it gets out of the stove. That's more internal passageway than the 118 and possibly as much as many base heaters.
Speaking of which. This old range did go 23 hours once, when I was away for an over-night in January a few years ago. I set it up my usual way for night heating mode and left at 1 pm. Got home at 12 noon the next day and it was still going. Just opened the dampers, gave it a good shake-down, added more coal and the old girl was rolling along within about the usual 10 minutes. Wish I knew why, . . and how to get it to run that long again.
Now tell me, . . how'd that big dinner you cooked on your base heater turn out ?
Just funnin'. I find this to be an interesting topic and I hope no one takes offence at my ribbing.