Williams Wall Furnace Heaters are compact, space-saving furnaces that are perfect for zone heating and where space is at a premium. They are available in 14,000, 22,000, and 30,000 Btu/hr sizes and are an economical option for people looking for zone heating. Compared to other wall furnaces, people like the Williams because of their upgraded looks and quiet operation. They are available in natural gas or propane and require no electricity to function.