This work presents a novel diode side-pumping scheme for Er:YLF with a characteristic laser emission at 2.81 μm. Average output powers greater than 10 W and corresponding pulse energies exceeding 100 mJ with a high slope efficiency of 18.7% are achieved. The Er:YLF laser efficiently operates at room-temperature cooling water and maintains a good beam quality of M2<12 in the major axis and M2<6 in the minor axis of the beam profile. The laser cavity is studied by means of Findlay-Clay analysis, and the operation at characteristic pump parameters is investigated. In addition, a dynamic laser rate equation simulation is introduced for quantitative and qualitative comparison. This compact and scalable free-running Er:YLF laser provides an effective building block for a subsequent Q-switching concept.