Some facts and figures.
From start up, December 31 through January 31 at 7PM, the system used 7.61 Tons of pellets.
Cost per Ton delivered was $172 so total fuel cost to heat 23,000 sq ft $1,308.00
Using DOE data of 16.5MMbtu per ton x boiler efficiency of 85% nets out to a bit under 107 MMbtu for the period of 32 days or roughly 3,330,000 btu / day......138,980 / hour.
Equivalent cost at local LP Gas price of $1.85/gallon
107MMbtu / 86,500 btu per gallon (net) = 1,237 gallon at a cost of $2,288
So just a hair under $1,000 less for pellets during the month of January.
When I figured the installed cost of and LP vs pellet system for him the difference was a wee bit over $28,000 additional.
I advised the owner that all other things being equal it would take him 5-6 years to pay back the difference.
The huge assumption there is LP prices remaining stable at <$2.00 per gallon. He was acutely aware of what happened during the brutal cold of last winter when LP prices went to $3.50+ because that's what his house runs on. He saw his YoY cost for gas nearly double from 2013 to 2014 and did not like to contemplate that happening in his work shop.
Last year heating about 8,000 sq ft he used a little over 2 semi loads of cord wood + the big CB would not produce enough heat to keep the shop at 60* buring wide open. Using wood to heat the whole building he'd would be looking at 5-6 loads at a cost of $4,000 - $4,500 to heat the whole 23,000 sq ft. Using his present time logs as a guide, the owner figured that would equal an average of 17 man hours per week labor for one of his guys at $15/hour. That adds about $13,000 annually to the cost of burning wood + maintenance on saws, fuel, chains, etc etc. Call it close to $14,000 using cord wood as the heat source.
In addition to that, he would have had to purchase at least one more OWB or a decent sized gasifier of some kind to crank out the required btu's.
That being said, If he would have gone to a gasification system with storage the fuel quantity would have been maybe 3-4 instead of 5-6 so labor costs would have been lower too.
In the end the labor costs with wood were the deciding factor for him.
In short for his particular case, pellets made the most sense.