Export loss

SELECT
    SUM(loss_ws) / 1000 / 3600 as loss_kwh, SUM(duration) AS loss_time_seconds
FROM (
    SELECT
        log_date, ((new_export_power - 9000)*duration) as loss_ws, duration
    FROM (
        SELECT *
        FROM (
            SELECT
                log_date,
                export_power + additional_power as new_export_power,
                (IF(@prevT IS NULL, 0, UNIX_TIMESTAMP(log_date)-@prevT)) as duration, @prevT:=UNIX_TIMESTAMP(log_date)
            FROM (
                SELECT
                    log_date,
                    grid_meter_active_power1 + grid_meter_active_power2 + grid_meter_active_power3 AS export_power,
                    pv_ppv * (8 / 20) as additional_power
                FROM pv_inverter_record
                ORDER BY log_date
            ) x, (SELECT@prevT:=NULL)prevT
        ) xx
        WHERE
            new_export_power > 9000
    ) xxx
) xxxx;