How Many Watts Is 1 HP? (And Why Motors Draw More)

The Standard Conversion: 1 HP to Watts

Understanding the conversion between horsepower (HP) and watts is crucial when sizing generators, selecting electrical circuits, or analyzing energy consumption. In the United States and for most electrical applications, the standard conversion is straightforward:

However, this is only part of the story. While 1 HP of output power equates to 746 watts, the actual input power an electric motor draws from your wall outlet is always higher due to efficiency losses.

Output Watts vs. Input Watts

It's important to distinguish between output and input power:

• Output Power (Mechanical): The work the motor actually performs (e.g., spinning a fan blade or pumping water). This is the HP rating on the nameplate.
• Input Power (Electrical): The total wattage the motor consumes from the power grid to produce that output work.

The Efficiency Factor

No motor is 100% efficient. Energy is lost as heat, sound, and magnetic field generation. Standard electric motors typically operate at 70% to 90% efficiency.

How to Calculate True Input Wattage

To find out how many watts a 1 HP motor actually draws, use this formula:

Worked Example: 1 HP Motor Draw

Let's say you have a 1 HP pool pump motor with a listed efficiency of 80% (0.80).

Output Watts = 1 HP × 746 = 746 Watts.

Input Watts = 746 / 0.80 = 932.5 Watts.

As you can see, a 1 HP motor can easily draw over 900 watts continuously, not 746 watts.

Quick Reference: Standard Motor Wattage Chart

The table below provides estimated continuous input wattages for typical residential single-phase electric motors, assuming average efficiencies.

*Note: These are estimates. Always check the Full Load Amps (FLA) on the motor nameplate for precise sizing.