Metric horsepower (PS, Pferdestärke) equals approximately 735.5 watts, slightly less than imperial horsepower, and is the standard power unit for vehicle ratings throughout Europe and Asia. Car specifications in Germany, Japan, and China typically list engine output in PS. One PS equals about 0.9863 imperial horsepower or 0.7355 kilowatts.

Calories per second (cal/s) equals exactly 4.184 watts, used primarily in thermodynamics and physics to express heat transfer rates. While not a common everyday unit, it bridges thermal and mechanical power calculations in scientific research. One calorie per second equals exactly 4.184 watts or about 0.00561 horsepower.