In this article, we carryout performance analysis on energy detectors in myriads of generalized fading environments. We utilize a new “exponential-type” contour and finite-range integral representations for the generalized M-th order Marcum Q-function QM(α,β) when its real order M>0 is not necessarily an integer. The accuracy of the new alternative integral representation for Marcum Q-function is validated using various existing representations. The form of the proposed integral representations (valid for real order M) facilitates its utility in various applications such as the evaluation of the receiver operating characteristics (ROC) of Bartlett periodogram (with/without zero padding) and the partial area under the ROC curves metric of Bartlett periodogram with/without diversity combining in a myriad of fading environments.