In a reciprocating quantum heat engine the working medium is a quantum system such as spin systems or an harmonic oscillator. For maximum power the cycle time should be optimized. There are two basic timescales in the reciprocating refrigerator the cycle time τ τ cyc and the internal timescale 2 π π / ω ω . In general when τ τ cyc ≫ ≫ 2 π π / ω ω the engine operates in quasi-adiabatic conditions. The only quantum effect can be found at low temperatures where the unit of energy of the device becomes ℏ ℏ ω ω instead of k B T . The efficiency at this limit is η η = 1 − − ω ω c ω ω h , always smaller than the Carnot efficiency η η c . At high temperature and for the harmonic working medium the efficiency at maximum power becomes η η = 1 − − T c T h which is the endoreversible thermodynamics result.