Part VIII: Wind, Water, and BiofuelsChapter 13. Biofuels, Wood, and Solar Cooking
Biomass Fuel Cost Comparison
Comparing cordwood, pellets, gas, and a heat pump on the same energy unit.
- Difficulty
- Beginner
- Cost
- Free
A cord, a therm, a gallon, and a kilowatt-hour are different boxes. The comparison that matters is the cost of a million BTU of heat that arrives in the room, after the stove, the furnace, or the heat pump has taken its share. Price without efficiency is how wood looks free and how a heat pump looks expensive before anyone does the division.
This page does not publish a 2026 price list. Fuel prices move, and a cord's energy moves with species and moisture. You type the price you pay, the energy in the unit you buy, and the efficiency of the machine that burns or pumps it. The starters in the form are arithmetic, not a quote.
The bill guide is where the therms and kilowatt-hours come from. The census puts a year of them in one pile. Burning the wood well enough to deserve its efficiency number is the wood page. Links below include other people's calculators and projects. Use them as outside reading, not as this form.
Difficulty
- Level
- Beginner
- Time
- An hour with prices and the nameplate or the EPA certificate
- Skills
- Dividing by efficiency before declaring a winner
Cost estimate
Free
You need prices you already pay or were just quoted. A moisture meter and an honest efficiency from a certificate are worth more than another forum guess. No national wood price is printed here.
Materials
| Item | Qty | Notes |
|---|---|---|
| The price of one unit you actually buy | Each fuel | Cord, ton of pellets, therm, gallon, or kilowatt-hour. Delivery and the truck you use are part of the wood price if you want the truth. |
| Energy in that unit | Each fuel | From a species table you trust, or the utility's own therm. Do not borrow a single 'hardwood cord' number for every pile. |
| Efficiency or COP | Each machine | The stove certificate, the furnace plate, or the heat pump's coefficient of performance. A fireplace with the damper bored open is not 70 percent. |
One unit
Delivered cost per million BTU is the price of the unit, divided by the million BTU in the unit, divided by the efficiency. A stove at 0.7 turns a cord's energy into seven tenths of heat in the room. An old open fireplace can be a tenth or worse and can even pull heated house air up the chimney. Use a poor number if that is the machine you have.
A heat pump is allowed a coefficient of performance above 1 because it moves heat rather than making it from the electricity. One kilowatt-hour is about 0.003412 million BTU. Put that in the energy box and put the COP in the efficiency box. Suppose, only as arithmetic, electricity were 15 cents a kilowatt-hour and the COP were 3. Delivered heat would be about 15 cents times 293, divided by 3, near 15 dollars per million BTU. As of 2026 that 15 cents is not a rate. Type yours. A COP of 3 is a stand-in, not your nameplate. Cold weather lowers the COP. Use the seasonal number if you have one, not the best laboratory point.
Gas furnaces often sit somewhere between the old 80 percent class and the condensing 90s. The plate on your furnace is the one that counts. Pellet stoves publish efficiencies too. A cord of wood might be near 20 million BTU when it is a dense, dry hardwood, and far from that when it is wet softwood. Look up the pile you have. The form's 20 is a filler so the division has an input.
Time and hassle are real and not in the form. Wood you cut, split, stack, and tend is not the same product as a thermostat, even when the dollars per million BTU look kind. Smoke, a chimney, and the hours are part of the decision. So is a heat pump that does not light a flue. The why-build page is the same honesty about projects that are worth doing for reasons other than the shortest payback.
Composite: wood is free
Invented household. They compare a cord someone gave them, entered as zero dollars, with a gas bill, and announce that wood won. They leave out the truck, the saw, the dry-storage roof, the sweep, and a stove efficiency closer to a smolder than to a certificate. The gas furnace was condensing and boring and expensive per therm until the efficiency went in. The composite lesson is to put a real price on the "free" cord, including the hours if the hours are the scarce thing, and to divide by the stove you have, not the stove in the advertisement. Not a real woodlot.
Write the price of one unit, delivered
Include the trip and the drying if the wood is not actually dry and stacked.
Write the energy in that unit from a source you can name
Species and moisture for wood. The utility's therm for gas. 0.003412 million BTU per kilowatt-hour for electricity.
Divide by efficiency or by COP
Certificate, nameplate, or an honestly poor number for an open fireplace. Do not use 100 percent.
Compare delivered heat, then compare the work
The cheaper million BTU can still be the one you will not tend. That is a valid reason to pick the other.
Further reading
These links go to outside sources. This book cites them by link and does not copy their words or pictures.
- https://www.builditsolar.com/Projects/BioFuel/biofuels.htm
- https://www.builditsolar.com/Projects/BioFuel/CatRetrofit/CatRetrofit.htm
- https://www.builditsolar.com/Projects/BioFuel/methane_nepal.html
- https://www.builditsolar.com/Projects/Cooking/cooking.htm
- https://www.builditsolar.com/Projects/WoodDrying/
- https://www.builditsolar.com/References/Calculators/Fuels/FuelCompare.htm
- https://www.builditsolar.com/References/Calculators/Fuels/HeatPumpCOP.htm
General education, not a permit or a stamped design. Follow the safety note in the guide, read the safety disclaimer, and hire a licensed trade when the work requires one.