Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to external fields and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes (|ΔT| ~ 1 K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict the existence of colossal barocaloric effects (isothermal entropy changes of |ΔS| ~ 100 JK-1 kg-1) in the energy material Li2B12H12 by means of molecular dynamics simulations. Specifically, we estimate |ΔS| = 367 JK-1 kg-1 and |ΔT| = 23 K for an applied pressure of P = 0.1 GPa at T = 480 K. The disclosed colossal barocaloric effects are originated by an fairly reversible order-disorder phase transformation involving coexistence of Li+ diffusion and (BH)12-2 reorientational motion at high temperatures.