Electrical Motors and Heat Loss

Heat gain from electrical motors to surroundings

Heat Loss from Electric Motors during Operation

Heat loss from electric motors due to inefficiency:  

Size of Motor
Heat Loss
0 - 2 75 250
3 - 15 85 150
15 - 150 90 100
150 - 92 80
  • 1 kW = 1.34 hp
  • 1 hp = 0.746 k W

Example - Heat Loss from an Electric Motor

Heat loss from a 10 kW electric motor can be calculated

(10 kW) (150 watts/kW)

= 1500 watts

= 1.5 kW

The rest of the energy

(10 kW) - (1.5kW)

= 8.5 kW

is converted to mechanical energy. 

If the motor and the mechanical equipment connected to the motor is in the same room - or enclosure - all energy at the end will convert to heat transferred to the room due to friction.

Heat Loss from Electric Driven Device to Room

The heat transferred to a room or enclosure depends on the location of the motor and the driven device. 

  • motor in room and driven device in room - all energy to the motor is at the end transferred to the room (heat loss from the motor and frictional energy from the driven device)
  • motor in the room and device outside room - only heat loss from the motor is transferred to the room - frictional energy from the driven device is lost outside the room
  • motor outside the room and device inside the room - frictional loss from the driven device is transferred to the room - energy loss from the electric motor is lost outside the room

Heat Loss - imperial units

Nameplate Rating
Motor Efficiency
Heat Loss to Room Air (btu/hr per rated hp)
Motor in Room
Driven Device inside Room
Motor in Room
Driven Devise Outside Room
Motor Outside Room
Driven Device inside Room
0 - 1.5 0.80 2542 508 2034
1.5 - 12.5 0.85 2542 381 2161
12.5 - 0.90 2542 254 2289
  • 1 Btu/h = 0.293 W 
  • 1 horsepower = 2542 Btu/hr

Related Topics

  • Electrical - Electrical units, amps and electrical wiring, wire gauge and AWG, electrical formulas and motors

Related Documents

Tag Search

  • en: electrical motor heat loss gain watts kw hk
  • es: motor eléctrico vatios ganancia pérdida de calor kw hk
  • de: Elektromotor Wärmeverlust Gewinn Watt kw hk

Search the Engineering ToolBox

- "Search is the most efficient way to navigate the Engineering ToolBox!"

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your SketchUp model with the Engineering ToolBox - SketchUp Extension/Plugin - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Translate the Engineering ToolBox!
About the Engineering ToolBox!