A thermoelectric device, or Peltier device, is a solid-state heat pump, a heat pump that uses electrical energy to move heat from one side of the device to the other side. Typically, the devices use ceramic substrates on both sides of the device with the semiconductor thermoelectric elements soldered between the two ceramic plates. These semiconductor elements pump heat individually when electrical power is applied. The elements can be wired in a number of series/parallel arrangements, but they work together to pump heat in one direction. The efficiency of the heat pump is measured by the amount of heat pumping provided compared to the electrical power used.