Ash Drawer Specifications: King (KE40) Real World Tested Performance (HHV) Cord Wood Max BTU˚˚ 57,000 Efficiency 81% (EPA listed efficiency) Maximum Heat input˚ 708.275 BTU’s Constant Heat output on High˚ 47,809 BTU’s/hour up to 12 hours Constant Heat output on Low˚ 14,343 BTU’s/hour up to 40 hours Square Feet Heated 1500 – 3000