Taking a homes kWh usage for a month and converting it to Wood BTU

[Plissken]

I have a home that past two years averaged 169 CCF over the coldest 5 months of the year.

So my season is 845 CCF. What is the proper method for extrapolating this out to the same amount of wood like White Oak, Hickory, Apple, Maple, etc. for sizing the load of wood I would need to keep on hand to make it through a season with an EPA certified add on furnace?

So it my math is correct:

So my 845 CCF is 84 million BTU's?

So I would need something like 5 cords of White Oak / Hickory / Apple? Properly split and seasoned to take into account about 65% real efficiency?

 

[Wood Duck]

With an outdoor furnace the calculations reveal about 6 cords. Ok, there were no calcs, but I bet I am close. I am sure you can Google the number of BTUs in a card of firewood, but have you accounted for all the inefficiencies in the new system? Is the 65% efficiency provided by the manufacturer? I bet real-life efficiency is lower than the reported value.

 

[Plissken]

I am looking at the Drolet Tundra and they have a stated optimum efficiency of 76%. So I was giving myself a fudge factor of ~12%.

I'm taking into account the chimney draft, the wood being used etc... Manufactures zealousness ;-)

I think I can net a cord of hardwood for about $70 per cord. So if I spend about $350 on wood heat for a winter it will be ~3 - 4 years to pay back the cost of the furnace in savings vs the $600-700 in natural gas.

Thanks for the napkin math to confirm my thoughts.

 

[CountryBoy19]

I am looking at the Drolet Tundra and they have a stated optimum efficiency of 76%. So I was giving myself a fudge factor of ~12%.

I'm taking into account the chimney draft, the wood being used etc... Manufactures zealousness ;-)

I think I can net a cord of hardwood for about $70 per cord. So if I spend about $350 on wood heat for a winter it will be ~3 - 4 years to pay back the cost of the furnace in savings vs the $600-700 in natural gas.

Thanks for the napkin math to confirm my thoughts.

Have you taken into account the inefficiency of your gas heat? If your gas is say, 90% efficient then really you're only putting about 75.6 MBTU into your home, and a 65% eff. wood heat would need 116 MBTU (4.5 cords of Oak). That assumes your 845 CCF = 84 MBTU (I didn't verify that).

 

[Plissken]

I do believe that 845CCF = 84 MBTU.

So 120 MBTU ~5 cords of white oak or shag bark hickory (common around Northern KY).

 

[Plissken]

Thanks everyone. You are all a great resource.