I recently caught a video from Woodruff Outdoors on YouTube explaining the savings with firewood. He did oil, gas and propane calculations. I have electric baseboard heat throughout my house, that I would use if it wasn't for my stove. So here are my calculations for electric compared to firewood. My types of firewood average about 22 million btu per cord. There are roughly 3400 btu per KWH. That comes out to 6470KWh per cord. I got my total rate per KWh by dividing my total bill by amount used. So total bill of 124.52 divided by 639KWh used comes to roughly 19 cents per KWh. So .19 per KWh multiplied by 6470 in a cord comes to 1229.00 dollars. So I can personally value a cord of wood for my heating purposes at roughly $1200. Correct? Or am I off with something?
Electric resistance heat is 100% efficient. Wood heat is not. So if you multiply your value per cord by the efficiency of your burning appliance, you will get a more realistic figure. So say $1229*0.8= $983/cord. If you wanted to get a little more into the weeds, you wouldn’t include your grid connection charge. Unless you truly have the ability to go off grid, you would retain that charge regardless..
Appliance efficiency, and also wood moisture content...so for wood at 20%, you take 20% off the available BTU's, if its 25%, you take 25% off. So if you use 22,000,000/cord as your average for the wood, then take 20% off for the moisture, and 20-30% off for the appliance...leaves you with 14,000,000 per cord if you have an 80% efficient wood burner (which is really good)
I wish I had your electric bill Pricey106. We had a few electric baseboard heaters when we moved in a 5 years ago. They were in the hall and a small bathroom. I took them out. Not really needed IMO. We have oil. With the current cost of oil and our old home, probably need 3 tanks a winter at the minimum, I think we're probably saving 4k at this point.
If I were to buy HHO @ $5.48/G, x 1000G/yr = $5,480 spent (not including electricity to run the furnace) OR I burn 6 cord of wood. Each cord is valued by me at $913.33. If I save $200/yr on electric for the furnace..... If I save $200/yr in electric because I cook on the wood stove when I can... $980/cord. Since I am not set up to sell, this is the way I heat my home. . . .
I was going to say efficiency of the wood burner, but others mentioned it. Many of the older stoves may only be in the 70-75% efficient range. Also the amount of MBTU's in each cord may not be achieved depending on MC in the wood.
I don’t think the relationship is quite so direct with respect to the moisture content. From what I have read, wood releases between 8600 and 9000 btu’s per pound of wood fully reduced. A pound of wood with 20% moisture content (dry method) has 0.2 lbs of water in it. Specific heat of water is 1 btu per pound. Heat if vaporization is 970 btu/lb and specific heat of steam is about .5 btu per pound. So 1 lb of wood coming from 20 degrees outside would need approximately 192*0.2*1.0 + 970*0.2 + 400*0.2*0.5 = 38.4+194+40=272 BTU’s to warm and vaporize the water inside (assuming flue gas temps around 600 degrees) at 20% moisture content resulting in 8328-8728 remaining BTU’s or 96.8-97% of the original heating potential. Reduce that by the appliance efficiency and I think you could determine a rough estimate of your overall efficiency when burning wood. Of course, over a certain moisture content would reduce efficiency until the point that combustion is not sustainable in a conventional heating appliance. Shoot holes in it at will.
Its pretty close though...good enough to get the average firewood hoarder in the ballpark. Here's an explanation, and a calculator...scroll down toward the bottom of the page for the calculator. Btu per Pound of Wood Calculator
Any idea what this statement is referring to? “Loss due to moisture from the combustion of hydrogen reduces the amount of potential Btu's by about 6% .”
I think that is referring to the moisture that is made by combustion...like how your car drips water out the exhaust until it gets hot enough to just evaporate the moisture...same with the newer HE gas furnaces...water is generated by combustion. I've always heard that hydrogen powered cars have only water as an "exhaust", or "waste" product.
Not to hijack the thread, but since this concept was brought up in relation.... So, the "20 degree wood....btu's needed to warm and vaporize the water inside........" Is this a major issue? Is this a large reason for people having wood racks inside? I thought that was mainly for convenience. I can understand it if the wood is that cold (frozen) it making sense to help the wood come up to temp...but is it a major deal if the wood is just cold, ie temps haven't been below freezing much (low-mid 30s and up)? I also get that you shouldn't put wood with ice/snow in the stove...
I don’t think it is a big deal. In my humble opinion, cold/frozen wood would only be an issue if it was not properly seasoned and had a high moisture content..
All the wood I burn is first stored in an indoor woodbin, in my root cellar, doesn't go below 45 in there, then brought near the stove, which I always keep about a 3 day supply.
If it helps to just dry the wood prior to burning it, putting it in a bin isn't a bad thing. Adds moisture to the air while it waits. Wood isn't a sponge but I find it has a complex setting when it is dry and then is subject to rain over time. Take a pallet for instance: they are often heat treated and dried out often in their journey all over used constantly. Then they hit a rain puddle or left outside after a load or two, it gets pretty soaked but after a few days of being out in dry weather it should be dried up enough again to burn. With all the explanation here is just to demonstrate that given that the wood was dry in the first place, it shouldn't have problems drying out near the stove. However even rain soaked wood has heaviness to it and might be easier to let it dry out before it gets dealt with again (i.e. moving from stack to stove). My wood covers often being tarps would have issues with side winds that really make it a PITA to deal with but I'm working on putting more weight on them and less fighting the rain and wind.
I see things the same way. Without wood heat, we'd be screwed with the cost of hho...What started out years ago trying to reduce heating costs by 25% a year turned into a lot more savings than I ever thought possible.
