Depending on what you burn wood in, it can be more expensive than coal, even if you get the wood for 'free'.
The expense of dealing with creosote, chimney cleaning, the bugs, dirt and snow tracked in every few hours to feed a wood stove. UGH! Repainting the rooms from the smoke yellowing, the constant smell of a wood fire. double UGH. Been there, done that. for many years.
In my outside boiler, the size of a wood fire to create enough heat is a pile of wood about like a wheelbarrow full. This lasts about 2-3 hours, If I fill the boiler's firebox [about 2-3 wheelbarrow loads] and damp down the air to the fire, then there is the smoke and creosote issue. This quantity will burn 6-7 hours. And the firet temperature fluctuates wildly, causing boil-overs or heat dumping.
With coal, I just loaded it up with 150# or so of coal, and left it alone for 10-12 hours, depending on how cold is was. MUCH easier than wood.
I have acres of free wood on my farm, it is so time consuming to cut, split and stack that I am better off paying for coal. I give away the wood usually.
I don't burn anything in the house, all burning is in the outside boiler in it's own 14'x20' building. I doubt if I'll ever burn in my house again.
So if I were to pay for good wood, oak, ash, maple etc split, and stacked, I'd be paying 2x or 3x as much as for coal. And I'd have to tend the fire every few hours.
I have this year converted my boiler from coal hand-feed to coal stoker-feed. This is even better, I fill the stoker's hopper once every day or two, and empty the ash pan twice a day. Done, thermostaticly controled, burns less 'cause it won't burn extra unless the aquastat calls for heat, it coasts during warm sunny days. A major improvement.
This summer I'm revamping my coal bin, and putting in 25-40 tons of coal, this way next winter will be mild or I will be prepared for whatever Mother Nature throws at us.