Final answer:
The BTUH output of a heater with a 20 kW rating is 68,240 BTU/hr, calculated by multiplying the kW rating by 3.412 BTU/hr per Watt.
Step-by-step explanation:
To determine the BTUH output of an electric heater rated at 20 kW, we use the conversion factor that 1 Watt is equivalent to 3.412 BTU per hour. Multiplying the heater's power rating by this conversion factor gives us:
20,000 Watts * 3.412 BTU/hr/W = 68,240 BTU/hr.
Therefore, a 20 kW electric heater has an output of 68,240 BTUH (BTU per hour).