Example of sidestepping NHibernate to bulk insert a bunch of test records into the database. This is lame but it's fast.

BulkInsert.cs

public static class BulkInsert
{
    private static SqlConnection Connection
    {
        get { return NHibernateSession.NHibernateSessionManager.Instance.GetSession().Connection as SqlConnection; }
    }

    public static void Meters(IEnumerable<EisMeter> meters)
    {
        var metersArray = meters.ToArray();
        var lastMeterId = (int) new SqlCommand("select max(id) from EIS_Meter", Connection).ExecuteScalar();

        var meterTable = new DataTable();
        meterTable.Columns.Add("Id");
        meterTable.Columns.Add("MeterNumber");
        meterTable.Columns.Add("ServiceMeterTypeId");
        foreach (var meter in metersArray)
        {
            meterTable.Rows.Add(++lastMeterId, meter.MeterNumber, meter.EisServiceMeterType.Id);
        }

        var bulkInsertMeters = new SqlBulkCopy(Connection) {DestinationTableName = "EIS_Meter"};
        bulkInsertMeters.ColumnMappings.Add("Id", "Id");
        bulkInsertMeters.ColumnMappings.Add("MeterNumber", "MeterNumber");
        bulkInsertMeters.ColumnMappings.Add("ServiceMeterTypeId", "ServiceMeterTypeId");
        bulkInsertMeters.WriteToServer(meterTable);

        Channels(Connection, metersArray.SelectMany(x => x.EisChannel));
    }

    public static void Channels(SqlConnection Connection, IEnumerable<EisChannel> channels)
    {
        var channelArray = channels.ToArray();
        var lastChannelId = (int) new SqlCommand("select max(id) from EIS_Channel", Connection).ExecuteScalar();

        var channelTable = new DataTable();
        channelTable.Columns.Add("Id");
        channelTable.Columns.Add("MeterId");
        channelTable.Columns.Add("ChannelNumber");
        channelTable.Columns.Add("ChannelTypeId");
        channelTable.Columns.Add("IntervalTypeId");
        channelTable.Columns.Add("PostivieFlow");

        foreach (var channel in channelArray)
        {
            channelTable.Rows.Add(++lastChannelId, channel.EisMeter.Id, channel.ChannelNumber,
                                  channel.EisMeterChannelType.Id, channel.EisIntervalType.Id,
                                  true);
        }

        var bulkInsertChannels = new SqlBulkCopy(Connection) {DestinationTableName = "EIS_Channel"};
        bulkInsertChannels.ColumnMappings.Add("Id", "Id");
        bulkInsertChannels.ColumnMappings.Add("MeterId", "MeterId");
        bulkInsertChannels.ColumnMappings.Add("ChannelNumber", "ChannelNumber");
        bulkInsertChannels.ColumnMappings.Add("ChannelTypeId", "ChannelTypeId");
        bulkInsertChannels.ColumnMappings.Add("IntervalTypeId", "IntervalTypeId");
        bulkInsertChannels.ColumnMappings.Add("PostivieFlow", "PostivieFlow");
        bulkInsertChannels.WriteToServer(channelTable);

        Usage(Connection, channelArray.SelectMany(x => x.EisChannelUsage));
    }

    public static void Usage(SqlConnection Connection, IEnumerable<EisChannelUsage> usages)
    {
        var lastUsageId = (long) new SqlCommand("select max(id) from EIS_ChannelUsage", Connection).ExecuteScalar();

        var usageTable = new DataTable();
        usageTable.Columns.Add("Id");
        usageTable.Columns.Add("ChannelId");
        usageTable.Columns.Add("DataTimestamp");
        usageTable.Columns.Add("DataTypeId", typeof(int));
        usageTable.Columns.Add("Data");
        usageTable.Columns.Add("IntervalTypeId", typeof(int));
        usageTable.Columns.Add("Receivedtimestamp");

        foreach (var usage in usages)
        {
            usageTable.Rows.Add(++lastUsageId, usage.EisChannel.Id, usage.DataTimestamp, usage.DataQuality, 
                                usage.Data, usage.EisIntervalType.Id, usage.Receivedtimestamp);
        }

        var bulkInsertUsage = new SqlBulkCopy(Connection) {DestinationTableName = "EIS_ChannelUsage"};
        bulkInsertUsage.ColumnMappings.Add("Id", "Id");
        bulkInsertUsage.ColumnMappings.Add("ChannelId", "ChannelId");
        bulkInsertUsage.ColumnMappings.Add("DataTimestamp", "DataTimestamp");
        bulkInsertUsage.ColumnMappings.Add("DataTypeId", "DataTypeId");
        bulkInsertUsage.ColumnMappings.Add("Data", "Data");
        bulkInsertUsage.ColumnMappings.Add("IntervalTypeId", "IntervalTypeId");
        bulkInsertUsage.ColumnMappings.Add("Receivedtimestamp", "Receivedtimestamp");

        bulkInsertUsage.WriteToServer(usageTable);
    }
}