One horsepower doesn’t exactly equal one horse. It’s a common misconception that one horsepower equals the peak power production of a horse. The maximum output of a horse is actuallyaround 15 horsepower, but that is only true for short periods of time. If you average the output of a horse over the whole duration of a work day, it comes closer to one horsepower. Watt defined one horsepower as "the amount of work required from a horse to pull 150 pounds out of a hole that was 220 feet deep". For the comparison, a human being is capable of approximately 5 horsepower of energy output at their highest level of power production.