Energy storage and heat deposition in Cr,Yb,Er co-doped phosphate glass were reported. A model based on rate equations was used to determine the energy storage from the free-oscillating output energy characteristics. The heat deposition was calculated by measuring the temperature rise of the glass rod. The results provided important information for the glass operating in Q-switched mode, and also for calculating the temperature profiles and cooling requirements of the glass under single shot and repetitive pulsed conditions.