def get_unmet_demand_hours(solution, carrier='power', details=False):
    """
    Get information about unmet demand from ``solution``.

    Parameters
    ----------
    solution : solution container
    carrier : str, default 'power'
    details : bool, default False
        By default, only the number of hours with unmet are returned. If
        details is True, a dict with 'hours', 'timesteps', and 'dates' keys
        is returned instead.

    """
    unmet = (solution['e']
             .loc[dict(c=carrier, y='unmet_demand_' + carrier)]
             .sum(dim='x')
             .to_pandas())
    timesteps = len(unmet[unmet > 0])
    hours = solution.time_res.to_pandas()[unmet > 0].sum()
    if details:
        return {'hours': hours, 'timesteps': timesteps,
                'dates': unmet[unmet > 0].index}
    else:
        return hours