Type of Submeter. All submeters installed in compliance with these regulations shall be of a type and class to properly and accurately register electrical consumption. The meter type and design shall meet the applicable provisions of the latest edition of the American National Standard for Electric Meters — Code for Electricity Metering, incorporated by reference in COMAR 20.50.02.02C. A submeter installed for billing purposes shall have been approved by the Commission. Charges for Electricity. All charges for electricity used by an occupant shall be calculated from the readings of his or her submeter. Meter Accuracy. All submeters in service shall be tested by the owner as provided by this chapter. Fast Submetering. If an occupant's submeter is found to be more than 2 percent fast as a result of a test, the owner shall: Recalculate the occupant's bills for the lesser of the period of the occupant's service or the period since the submeter was last tested. Make a refund or a credit to the occupant, if the adjustment so calculated exceeds $1. Slow Submeter. If a submeter is found to be more than 2 percent slow as a result of a test and the unbilled amount exceeds $5, the owner may bill the occupant 1/2 of the unbilled error for the period of the occupant's service, or since the submeter was last tested, whichever is less, but not for a period longer than 12 months. Accuracy Calculation. The average accuracy shall be the weighted average of the percentage registration at light load and at heavy load, giving the light load registration a weight of 1 and the heavy load registration a weight of 4. Overcharge Adjustment. If an occupant has been overcharged as a result of an incorrect submeter reading, incorrect calculation of the bill, or incorrect submeter connection, the owner shall credit or refund the amount of overcharge to the occupant. Undercharge Adjustment. If an occupant has been undercharged as a result of incorrect submeter reading, incorrect calculation of the bill, incorrect submeter connection, stopped submeter or similar reasons, the amount of undercharge may be billed to the occupant. Meter Test by Owner. Upon application by occupant, the owner shall test the submeter for accuracy, at a laboratory approved by the Commission or on-site with instruments approved by the Commission, with no charge to the occupant, provided that no test was made within the past 18 months. Testing upon Installation and Removal of Meters. A submeter may not be placed in service until it has been tested and adjusted by the owner at a laboratory approved by the Commission or on-site with instruments approved by the the Commission to within plus or minus 1 percent of 100 percent accuracy. If any submeter is removed from service or replaced by another submeter, it shall be properly tested and adjusted by the owner at a laboratory approved by the Commission before being placed in service again.