The best firewood is the densest hardwood you can get locally, properly seasoned. Hickory, white oak and beech lead on heat output, and a cord of hickory holds roughly twice the energy of a cord of cottonwood.
That factor of two is the single most useful thing to know about firewood species. It means two cords at the same price can be very different purchases.
Heat output by species
| Species | Type | Million BTU per cord | Seasoned weight (lb) |
|---|---|---|---|
| Hickory | Hardwood | 27.7 | 4,327 |
| White oak | Hardwood | 25.7 | 4,200 |
| Beech | Hardwood | 24.0 | 3,760 |
| Red oak | Hardwood | 24.0 | 3,757 |
| Sugar maple | Hardwood | 24.0 | 3,757 |
| Birch | Hardwood | 20.8 | 3,179 |
| Douglas fir | Softwood | 20.7 | 2,970 |
| Ash | Hardwood | 20.0 | 3,440 |
| Cherry | Hardwood | 20.0 | 2,928 |
| Elm | Hardwood | 20.0 | 2,872 |
| Red maple | Hardwood | 18.6 | 2,900 |
| Pine | Softwood | 15.9 | 2,236 |
| Spruce | Softwood | 15.0 | 2,100 |
| Aspen | Hardwood | 14.7 | 2,295 |
| Cottonwood | Hardwood | 13.5 | 2,108 |
The two columns track each other closely, and that is the whole principle: you are buying wood substance, and heat follows density. A pound of dry wood releases roughly the same energy whatever tree it came from. A cord of hickory simply contains more pounds of it than a cord of spruce.
Which means the species question and the weight question are the same question. There is more on that in how much a cord of wood weighs.
The top tier
Hickory is the highest heat firewood in common use at 27.7 million BTU per cord. It burns hot, holds a fire overnight, and is difficult to split by hand. Where it grows it is usually priced accordingly.
White oak and red oak are the backbone of the eastern US firewood market: plentiful, dense, long burning. The catch is seasoning time. Oak needs a full year split and stacked, and dense white oak often two. Oak bought in September and burned in November is green wood, whatever the seller called it.
Beech and sugar maple sit alongside oak on heat and season somewhat faster. Beech in particular is excellent firewood that gets less attention than it deserves.
The practical all rounder
Ash is the wood experienced burners tend to name when asked. It is not the highest heat on the table, but it splits cleanly, seasons in six to nine months rather than two years, and burns hot and clean.
There is also a great deal of it available in the eastern US, for an unhappy reason: emerald ash borer has killed ash across much of its range, and salvaged ash is common and cheap. This is also exactly why firewood transport is regulated. Moving ash out of a quarantine county is how the beetle spreads. Buy it locally, burn it locally.
Where softwood earns its place
Softwood is not bad firewood, it is different firewood. Pine, spruce and fir carry less energy per cord because they are less dense, and they burn fast.
That fast bright burn is exactly what you want for:
- Kindling and getting a fire going, where hardwood is slow to catch.
- Shoulder season fires in October and April, when a hot short fire beats banking dense hardwood you do not need.
- Any fire you want hot quickly and do not need to last.
In much of the Mountain West and Pacific Northwest, softwood is what is available and what everyone burns. There is nothing wrong with that, provided the price reflects the lower heat content per cord, and provided you expect to burn more cords for the same warmth.
The persistent claim that burning pine causes chimney fires is a misunderstanding. Creosote forms when wood burns cool and smoky, which is a function of moisture and how the stove is run, not of resin. Seasoned pine burned hot is clean. Wet oak burned smouldering is not.
What not to burn
Some of these matter for your health rather than your heating bill:
- Treated, painted or manufactured wood. Pressure treated lumber, plywood, particle board, MDF and pallets of unknown origin. They release toxic compounds when burned, indoors or out.
- Driftwood. Salt corrodes flue liners and stove internals, and burning it releases chlorine compounds.
- Poison ivy, poison oak, oleander. The irritant oils carry in the smoke and are genuinely dangerous to inhale.
- Anything mouldy or rotten. It has already lost much of its energy to decay and the spores are unpleasant to handle.
- Green wood of any species. Not dangerous, just wasteful and dirty. See seasoned versus kiln dried.
Species and what you should pay
Since a cord of hickory holds roughly twice the heat of a cord of cottonwood, paying the same for both means paying twice as much for the heat you actually get. Mixed hardwood is a legitimate product, but it is a mix, so assume the cheap end of it when pricing.
Ask the species before comparing two quotes, then put both through the firewood cost calculator, which adjusts for heat content and normalises face cord and half cord quotes to a price per full cord. It is the only way to see which of two numbers is genuinely the better deal.
Regional availability sets much of this. The Northeast burns oak and maple, the South burns oak and hickory, the Mountain West burns pine and fir, and prices follow both the species and the freight. See firewood prices by state for the regional picture.