Whether you have just acquired a new coal-fired stove or have been using one for decades, understanding the right type and size of coal is paramount. Anthracite is considered the most appropriate coal type for home heating. Notably, though, having to choose between the numerous different anthracite coal sizes available may prove to be confusing.

In this guide, we look at these different sizes and determine the right one for different types of coal stoves and how to choose the most suitable one.

What Is Anthracite?

Anthracite refers to the highest-ranked type of coal in terms of metamorphism, with the highest energy density compared to other types of coal. It has a semi-metallic shiny black luster and is harder and purer than bituminous coal, odorless and steady in its burn. It comes in at least eight standard sizes, generally categorized into two sizes, larger and smaller.

Larger Sizes

  • Egg: Comparable to a softball in size, egg is one of the largest sizes available (between 2 7/16” and 3 ¼”). Egg is not very common and is often omitted in some classifications.
  • Stove: Stove is equivalent in size to a baseball (between 1 5/8 and 2 7/16”) and is one of the most popular sizes in the large coal segment.
  • Chestnut: Often referred to as nut, the chestnut size is slightly larger than a golf ball (13/16” to 1-5/8”).
  • Pea: Comparable to a quarter (9/16” to 13/16”), the pea finishes up the larger sizes of coal.

Among these larger sizes, stove, chestnut, and pea are the most popular choices. The three have a moisture level of about 5% and ash ranging between 8% and 10%. Their range of volatility is between 4% and 4.5%, while they have about 85% to 88% fixed carbon. Nut and stove are the most preferred sizes for hand-fired appliances. Pea is used in our Coal Gun coal stoker boiler.

Smaller Sizes

  • Buckwheat: Also known as buck. It is the largest among the smaller sizes and is about the same size as a dime (5/16” to 9/16”).
  • Rice: Roughly equivalent to the size of a grain of rice (3/16” to 5/16”), rice is the second smallest category by most classifications.
  • Barley: This is generally the smallest category available and is about the size of a coarse grain of sand (3/32” to 3/16”).

These three smaller sizes have varying moisture levels, ranging from 6% for buck to 7% for rice, and 8% for barley. They have between 10% and 13% ash and 82% to 86% fixed carbon. They are most popularly used in automatic stokers, which refer to stoves that support the mechanical feeding of coal. This size is generally said to burn better than larger sizes due to the large surface area that allows for greater circulation of oxygen. However, this is subject to using the size best suited to your type of stove.

How to Choose the Right Size of Coal

Efficiency and overall performance mostly revolve around using the right coal size for your particular stove model. To determine this, check and follow the recommendations from your manufacturer. Notably, some stoves accept several different coal sizes and come with instructions. Compare the performance of the acceptable sizes to get the best heat output and durability.