Consideration of some Components for Firewood Economics

Author: Martin Twer
Update: 2/14/2014

This is an online adaptation of MontGuide MT8411.
It provides an estimate how much heating your home with a "traditional, open-faced fireplace" is costing you, and if/how much investing in a new, EPA-certified wood stove could potentially save you over time.
You can also estimate if substituting your existing fuel source with firewood would make financial sense at current market prices.

All default values can be changed!

STEP 1 - Calculate the Unit Cost of your current Fuel

Look at your utility bills to find the total energy charge for a given time period (e.g. month, quarter, semi-annual, annual) for the fuel used for home heating. 
For example, if you heat your home with natural gas, and your utility bill shows two fuels - e.g. electricity and natural gas - use the charge shown for natural gas only. 
To determine the per-unit-cost of your fuel, enter the amount (in USD) you were charged, and the amount of fuel used for a given time period.
The cost of fuel (per unit of fuel) is generally expressed as: $/gallon for heating oil, $/therm (or ccf) for natural gas, $/kWh for electricity, $/gallon for propane, $/ton for coal.

Example: Assuming 53 MMBTU (15,533 kWh) as average annual heating demand, estimates for a household could be

Amount charged Amount of Fuel used Fuel Type
$1,860 477 gallons #2 Heating Oil
$1,744 15,850 kWh Electricity
$2,050 683 gallons Propane
$590 625 therms Natural Gas

 

 

Amount charged Amount of Fuel used   Cost per Fuel Unit
 
If only a portion of this Fuel is used for space heating, enter the estimated percentage here: %

STEP 2 - Calculate the Costs per 1,000 BTU (British thermal units)

What fuel are you currently using to heat your home?

Heating Oil
LPG/Propane
Natural Gas
Coal, Bituminous
Electricity

Conversion Factor   Cost per 1,000 BTU

STEP 3 - Determine the Heat Yield from the Wood you are planning to burn.

The heat yield is the amount of heat that you can actually capture from burning wood (air-dried, 20% Moisture Content) in your stove. It is expressed as 1,000 BTU/cord.

What kind of wood are you burning predominantly?

Aspen
Birch
Cottonwood
Cedar, Western Red
Douglas Fir
Fir, Subalpine
Fir, Grand
Hemlock
Tamarack/Western Larch
Pine, White
Pine, Lodgepole
Pine, Ponderosa
Spruce


What is the overall efficiency of your wood burner?
Examples:

EPA-certified Catalytic Wood Stove (72%)
EPA-certified Non-Catalytic Wood Stove (65%)
Single Stage, airtight Stove (40%)
Franklin-type Stove (30%)
Improved Fireplace (20%)
Open Fireplace (10%)

Gross heat (MBTU/Cord) Combustion Efficiency   Heat Yield (MBTU/Cord)
 %
 
The amount of the selected wood species with a Heat Value Equivalent calculated from step 1 (Amount of Fuel adjusted for Percent used for Space Heating), would be approximately  cords.

STEP 4 - Determine the Break-Even-Value (BEV) for purchasing Firewood

The BEV is defined as the amount of money you can spend for a cord of firewood to break even on your current utility bills. If you can obtain a cord of firewood for less, then the difference is how much you will save per cord of wood burned.
If you are spending more for wood than the BEV, you are subsidizing your bill and would be better off economically to heat with other fuels.


    Break-Even-Value
   /cord

However, in order to compare the BEV with the price paid for firewood (if purchased), the cost of the wood stove should be considered as well. In an analysis of this type you should consider the costs on a "per cord burned" basis, which we will do below.


STEP 5 - Determine the Cost of a Wood Burning Unit on a per Cord Basis

Cost of wood burning unit (purchase, installation, BOS)
Annual maintenance costs
Expected lifetime of wood burning unit  years
Expected number of cords burned per year
Costs per cord  $ 

STEP 6 - Determine Chain Saw Costs on a per Cord Basis

Chain saw costs (Fixed)  
Chain saw
Maintenance, repairs and personal protective clothing
Salvage value
Expected lifetime of chainsaw  years
Fixed Costs per Cord  $ 
   
Chain saw costs (Variable)  
2-cycle Gasoline/Oil Mix (1 gal/cord)
Bar Oil (1/2 gal/cord)
Chain (assuming new chain (@$25) every 10 cords)
Variable Costs per Cord  $ 
   
Total Chainsaw Costs per Cord

Total Equipment Cost per Cord

 $ 

STEP 7 - Determine Transportation Costs

Transportation costs are those costs associated with hauling a cord of wood from the forest to your home. The amount is calculated on a cost per mile per cord hauled. You will need to know your total cost/mile to operate your truck (including depreciation, maintenance, and fuel) and its capacity.

A cord is a stack of wood that has a volume of 128 cubic feet (4x4x8 feet); depending on the tree species and moisture content of the wood a cord weighs between 2,500 and 3,500 pounds (1.25 - 1.75 tons).

Assume the following:

Truck type Capacity in cords
1/2 ton (1-foot side racks) 1/2 to 3/4 (.5 to .75)
3/4 ton (2-foot side racks) 3/4 to 1 (.75 to 1)
1 ton 1 to 1 1/4 (1 to 1.25)
2 ton 2 to 2 1/4 (2 to 2.25)

 

Truck capacity  cord(s)
Truck cost/mile
Transportation Costs per Mile per Cord  $ 

STEP 8 - Determine the Maximum Round Trip Mileage (MRTM)

The maximum round trip mileage that you can drive to gather your own wood is calculated by subtracting your total equipment cost per cord (step 6) from the break-even-value (Step 4) of the wood. 
By dividing this difference, called maximum allowable transportation cost (MATC), by your cost per mile per cord (step 7), the quotient is your maximum round trip mileage.

 
Maximum allowable transportation cost (MATC)
Maximum round trip mileage (MRTM)

Reducing Transportation Costs

The only significant way to reduce the costs of gathering your own firewood is to minimize your transportation costs.
Consider doing this:

  • Use a large truck to haul your wood. The cost/cord/mile is lower on a large truck provided it is filled to capacity. You might want to scout out potential wood in a small truck before cutting.
  • Keep spare parts for your chain saw. You can easily waste $15 to $20 for gas to drive to the woods and back if your starter rope breaks on the first pull.
  • Tow a trailer behind a two wheel drive 3/4 ton (or larger) truck. You will be able to almost double your wood hauling capacity at a fraction of the cost.
  • Do not overload your vehicle. Haul at capacity, but do not abuse your vehicle. Vehicle breakdowns are a sure way to very expensive firewood.
  • Work and drive safely.
  • Enjoy getting out into the forest for recreation and exercise. Remember, you are not paying yourself a wage for this work!