The numbers on the left side of the graph show either the brake horse power or the kilowatts being consumed. You can select the appropriate units for your application. If the fluid has a higher or lower specific gravity we must multiply the number on the left hand side of the graph by the specific gravity number to get the correct horsepower or kilowatts for your applicatioin. If the pump was sized correctly for the application, it would run within ten percent of its best efficiency point. A service factor of 1.15 - this is the most common service factor used in modern motors.
Motors are available in a variety of horsepower and kilowatt ratings.
Keep in mind that any heat generation computations made by the motor manufacturer were made for the motor when it was running at its rated horse power and not at the service factor rating. All this means is that the motor will run hotter than anticipated, but still within acceptable limits. This organization specifies that the factor should be used as an additional safety margin. There are instances where you can combine the two service factors and come up with a compromise. Electric motors are sized considering the specific gravity of the liquid being pumped.