Understanding British Thermal Units
Pellet stoves, while providing you with warmth and comfort, do not exactly come cheap. Even used or refurbished units can easily cost at least US$1,000 so it pays to closely scrutinize and evaluate the particular model and unit you plan on buying.
Pellet stoves are first and foremost intended for heating. Heat output range or heating capacity, therefore, should be your first consideration. This is typically measured in BTUs or British Thermal Units. One BTU is the energy needed to raise the temperature of one pound of water by one degree Fahrenheit.
BTU can be used to refer to the heat value or energy content of fuels such as pellets. Pellets made from white oak, for example, have a BTU rating of 8,800 per pound, while that of yellow pine is higher at 9,600 BTUs. This means that a pound of white oak pellets can raise the temperature of 8,800 pounds of water by 1°F.
When applied to heating or cooling power, however, the measurement is more properly expressed as BTU per hour. Often, however, this is simply abbreviated to BTU but context will tell you what is actually meant. The addition of “per hour” reflects the amount of time it takes for a heater or cooler to use or put out its BTU rating. A pellet stove, for instance, operating with a heat output of 10,000 BTUs per hour will take a little less than one hour to burn a pound of yellow pine wood pellets. What it actually tells you is how much fuel it burns, not how much heat it introduces into the room.
Pellet stoves often have a heat range starting at a low 8,000 to a high of 90,000 BTUs per hour. This will vary from one brand or model to the next. What you actually need depends on a number of factors –size and configuration of room to be heated, status of insulation, location in the country, and even your personal comfort level.