We are pursuing this credit but meters in Spain are not calibrated nevermore once they are installed. When they are revised they are substituted if needed or every 4 years for example. So we can obtain the "accreditation certificate" by an external company verifying the calibration of the meter when it was installed, could it be enough to verify the correct operation of meters? if there is a meter that was changed before the performance period and it only was in operation for four years, do we have to substitute it?