The three grades
PFI residential grades are set mainly by ash content: Premium at 1 percent or less, Standard at 2 percent or less and Utility at 6 percent or less. Grades also cover bulk density, durability, fines and chloride. Sources describing the program give moisture limits of 8 percent for Premium and 10 percent for the other two.
Why ash is the one you feel
Ash is what stays in the burn pot and the ash pan. Higher ash means cleaning more often, and it can clog a stove that was set up for low-ash fuel. Pellets from different mills also burn differently, so try a few bags before you buy a full ton.
What to look for on the bag
Check for a PFI mark and a grade, not only the word “premium”, which any bag can print. Keep the bags dry and off the floor, since pellets swell and fall apart if they take up moisture.
Where this site stands
We review the stove, and the fuel shelf is not open yet. Where a pellet stove listing says which grade it needs, we repeat it in the review.
Questions that keep arriving by post
Will a pellet stove burn Standard grade pellets?
Many will, but the manual decides. A stove built for Premium may need more frequent burn pot cleaning on higher-ash fuel, and low-grade fuel can affect a warranty.
Does hardwood mean better pellets?
Not on its own. Softwood pellets can match or beat hardwood on heat and ash. Grade and test data tell you more than the species named on the bag.
Last reviewed November 1, 2026