How Electric Reefers Work: A Comprehensive Guide

Electric Reefers grew in popularity because of steep diesel fuel price increases and because of the problems and high expenses to keep old diesel engine powered reefers running. Sometimes emissions law changes came into play as well.

Main Takeaways

  • Electric reefers are powered by electricity instead of by a diesel engine. Otherwise they work almost identically to diesel engine powered reefers.

Key Components of an Electric Reefer System

Electric reefers use AC versions of electrical components. Non electric components are very similar to diesel reefers.

Power Source

Electric reefers are powered by electric.  AC electric that would come from an electrical plug.  This is sometimes called shorepower or a dedicated circuit.  This means they have to be plugged in.

  • The electric plug must be 3-phase/50-60Hz.
  • It may be either 230 Volt (also known as a range of 220 Volt to 240 Volt), or 460 Volt (also known as a range of 440 Volt to 480 Volt).
  • Circuits must be dedicated to the electrical opening (or plug) that the electric reefer will be plugged in to.  230 Volt units require 60 amp openings to furnish continual 30 amps.  460 Volt units require 30 amp openings to furnish continual 15 amps.

Digital Control System

Controls are commercial style.  They receive power by low voltage AC current and not the 12VDC you typically see with diesel powered units.

  •  Temperature setpoint adjustments.
  • Alarms and defrost cycles.
  • Remote monitoring (depending on model).


Condenser Coil & Fan

Condensers and their fans release heat removed from the inside the trailer to the external environment.  These components are very similar to what  is used with nearly all units made for trailers.  The difference with electric reefers is that they use a drive motor fed by AC electric current.

Evaporator Coil & Fans

Evaporators and their fans absorbs heat from inside the reefer; fans ensure uniform airflow around the cargo. These too are very similar to what is used with nearly all units made for trailers.

Electric Power Module

Ensures reliable operation for electric supply and protects the unit from surges or incorrect wiring.

This module includes:

  • Power inlet and circuit protection.
  • Contactors/relays.
  • Capacitors or soft-start equipment.
  • Disconnect switch.

Putting it All Together

To summarize, the components of electric reefers perform the same temperature control functions that diesel reefers components do.   The difference with Electric Reefers is with the components that require electric inputs.  These are changed to the types that take AC electricity because of power coming from the electric grid (as opposed to DC electricity from batteries on diesel units).

Who Should Consider Electric Reefers?

Anyone using stationary semi-trailers for temperature control for storage trailers while they are not moving will be a fit for using electric reefers. Any one using engine powered TRU’s for storage semi trailers.

  • Example. Any one using engine powered Thermo King units for storage semi-trailers.
  • Example. Any one using engine powered Carrier units for storage semi-trailers.