When purchasing a treadmill, motor horsepower is an important consideration. Horsepower is basically how much power the motor can produce. In terms of treadmills, you should be concerned with the motor CPH, which is the motor's ability to put out continued power.
Generally speaking, more horsepower means a larger motor which means a higher cost. A treadmill with less horsepower can cost less but offer a much smaller speed range.
The best treadmill motor for you depends on your personal goals and what you’ll be using the treadmill for. Manual treadmills are also available at a fraction of the cost due to the absence of a motor.
Motors up to 2.0 CHP are suitable for walking which would be up to 5 mph. Motor from 2-3 CHP can cater to jogging speeds to around 8-10 mph whilst motors over 3.0 CHP can produce belt speeds over 10 mph for running.