What is the cost of pellet fuel relative to other fuel types?
Pellets have remained very price stable over the years, with most increases coming from freight costs. Each installation is likely to have a different efficiency. If an efficiency is published for an appliance it is in a lab setting with ideal fuel and conditions. Variances in delivery of heat also affect comparison as in the case with changing from a central heat system as primary to a single point heat source such as a stove. All of that said the cleanest comparison we can recommend is a pure btu rating. From there you can determine (but keep in mind it that for the most part you are guessing or speculating which will be more/less efficient) how one might compare to the other for your situation.
