A reference is required to record electroencephalography (EEG) signals, and therefore the reference signal can effect any quantitative EEG analysis. In this study, we investigate the impact of reference signal amplitude on a commonly used quantitative measure of the EEG, the signal energy. We show that: (i) when the reference signal and the non-referential signal have negative correlation, the energy of the referential signal will monotonically increase as the amplitude of the reference signal increases from 0 to ∞. (ii) When the reference signal and the non-referential signal have positive correlation, energy of the referential signal first decreases to some nonnegative value and then increases as the amplitude of the reference signal increases from 0 to ∞. In general, the reference signal may decrease or increase energy values. But a reference signal with higher relative amplitude will surely increase energy values. In , we developed a method to identify and extract the reference signal contribution to EEG recordings. Here we apply this approach to referential EEG recorded from human subjects and directly investigate the contribution of recording reference on energy and show that the reference signal may have a significant effect on energy values.