The Keystone 12,000 BTU 230V through-the-wall air conditioner with 10,600 BTU Supplemental Heat Capability is perfect for rooms up to 550 square feet. In addition to cooling, this versatile unit also offers supplemental heat capability, providing you with an additional heat source to your main heat source when outdoor temperatures are above 23 degrees Fahrenheit. It has electronic controls with LED display and a temperature sensing LCD remote control allowing you to conveniently see, set and maintain the room temperature from across the room. Money saving features include energy saver mode, sleep mode and a programmable 24-hour timer. This unit is designed for through-the-wall installation and is not designed for standard window installation (WALL SLEEVE SOLD SEPARATELY). This unit also requires a special 230-volt/20-amp electrical outlet and will not operate with a standard 115V household electrical outlet. Supplemental Heating mode meant to be operated when temperatures outside are between 23 & 76 degrees. Mode is supplemental and NOT meant as primary heat source.