For those who were wondering…
According to US publication Mother Earth News, the heat output of 1 ton of wood pellets (907kg) = approximately 1 cord of wood.
Note, this is the US regulation definition of a cord, which is efficiently stacked, not loosely tossed as in NZ. Fortunately, to help us out here, under Maine law, stacked and loose cords are defined as 128 cu ft vs 195 cu ft respectively. This amounts to a ratio of pretty much 1:1.5. Therefore a standard Christchurch-purchased cord of firewood (tossed, not stacked) equates to approximately 600kg of pellets.
At $0.58 per kilo, you are paying $348 to buy pellets in Christchurch equivalent in heat output to a tossed US cord of wood.
As of today, a cord (3 cubic metres) of a mix of dried pine and oregon in Christchurch is $285. Converted to a US cord of 3.6 cubic meters, you get a cost of $342.
Assuming the above assumption on heat output equivalence is based on a pine & oregon firewood mix, $348 of pellets = $342 of firewood.
On this basis, heat from a pellet stove is equivalent in cost to heat from a firewood stove. This ignores the minor electrical cost of running the fan in a pellet stove.
Sources of assumptions that went into this calculation:
- Relative heat output http://www.motherearthnews.com/renewable-energy/wood-pellet-stoves-zb0z1211zsor.aspx#axzz2y5Vryxsu
- Stacked vs loose cords defined in Maine http://en.wikipedia.org/wiki/Cord_(unit)
- Cost of pellets in Christchurch http://eenergy.co.nz/cart#.U0EElfmSx8E
- Cost of firewood in Christchurch http://www.cityfirewood.co.nz/index.php?route=product/product&product_id=422