def max_power_rule(mod, prj, tmp):
    """
    **Constraint Name**: GenVarStorHyb_Max_Headroom_Power_Constraint
    **Enforced Over**: GEN_VAR_STOR_HYB_OPR_TMPS

    The project's power and upward reserves cannot exceed the available
    capacity.
    """
    return mod.GenVarStorHyb_Provide_Power_MW[prj, tmp] \
        + mod.GenVarStorHyb_Upward_Reserves_MW[prj, tmp] \
        <= mod.Capacity_MW[prj, mod.period[tmp]] \
        * mod.Availability_Derate[prj, tmp]