The Haydon HB750-7FA Heat Base 750 is a hydronic baseboard heater designed for residential heating applications. The "750" in the model number typically indicates the length of the baseboard in inches, which is 7.5 feet (or 90 inches) in this case. The heat output of a hydronic baseboard heater is typically measured in British Thermal Units (BTUs) per hour. The specific BTU output of the Haydon HB750-7FA model can vary depending on factors such as the water temperature, flow rate, and other design considerations. As a rough estimate, you can calculate the approximate BTU output based on the length of the baseboard. A common rule of thumb is that a hydronic baseboard heater produces around 600-700 BTUs per linear foot of length under normal operating conditions. For the Haydon HB750-7FA model, with a length of 7.5 feet, the approximate BTU output would be: 600 BTU/ft * 7.5 ft = 4500 BTUs 700 BTU/ft * 7.5 ft = 5250 BTUs So, the estimated BTU output of the Haydon HB750-7FA Heat Base 750 would be between 4500 and 5250 BTUs per hour under typical conditions. However, for precise information on the BTU output of this specific model, it's best to consult the manufacturer's specifications or contact the manufacturer directly.