def add_capacity_factor(variable_component_names, **kwargs):
    """Add capacity factor to :py:obj:`variable_component_to_load_names`.

    :param variable_component_names: Names of components to load per
      variable.
    :type variable_component_names: mapping from :py:class:`str`
      to collection

    :returns: Names of components to load per variable with
      capacity factor added.
    :rtype: mapping from :py:class:`str` to collection
    """
    variable_name = 'capacity_factor'
    variable_component_to_load_names = variable_component_names.copy()
    if variable_name in variable_component_names:
        variable_component_to_load_names.update({'generation':
            variable_component_names[variable_name], 'capacity':
            variable_component_names[variable_name]})
        del variable_component_to_load_names['capacity_factor']
    return variable_component_to_load_names
