You burn wood, and smoke goes up flueway.
You're not running chimney smoke through ductwork so you have a heat exchanger.
What kind of heat exchanger?
probably air since you're running through ductwork?
How much hot air or hot water is coming off heat exchanger?
How big of a space can be heated with that amount of heat?
Is the exchanger located in optimal location?
One room log cabin with fireplace will not stay very warm.
One room house with big wood burning stove in center, with hot flue pipe running across the room and exiting on far wall, will get warm-hot, but will cool off fast.
Because the BTU output of firewood is much less than electric, coal, oil, or gas.
Otherwise they would have made wood-burning steam locomotives. But the locomotive boiler cannot get hot enough with wood ... the boiler needs coal to produce enough BTUs to boil water fast enough to rotate the turbine and turn the wheels.
Maybe your wood stove output should be measured.
Don't forget a huge percentage of fire heat goes straight up flueway.