The Boss Therm Programmer BUP 2 Universal Programmer is a white, programmable storage tank water heater designed for wall mounting indoors. It is powered by lithium batteries and has an energy efficiency rating of A. This unit does not have a tank lining material or a tank capacity, but it offers a 1-month manufacturer warranty. The programmable feature allows for easy scheduling and control of the heating system, making it a convenient and efficient choice for keeping water hot in your home.