Pellet fuel grades
Wood pellets are graded chiefly by ash content and consistency: PFI Premium pellets run under 1% ash, Standard up to 2%, and Utility up to 6%. Pellet stove warranties and clean operation generally assume Premium-grade fuel.
Pellets are made of compressed sawdust with no binders; grade differences come from bark content and raw material. Low-ash premium pellets keep burn pots and heat exchangers clean, extend intervals between cleanings, and keep the certified emission performance realistic.
The Pellet Fuels Institute (PFI) standards program prints the grade on the bag. Softwood vs hardwood matters far less for pellets than for cord wood — softwood pellets often have slightly higher heat content and lower ash.