What are the metering requirements?

Accuracy Requirements

Metering equipment must meet the accuracy requirements of ISO New England Operating Procedure No. 18 or any successor thereto or the Small Generator Metering Protocol specifications (below) per NEPOOL GIS Rule 2.5(j).

Minimum Accuracy Requirements Only "revenue grade" (also called "revenue quality") meters tested and certified to ANSI C-12 standards are allowed. Minimum accuracy and other requirements, based on nameplate capacity, are as follows:
Nameplate Capacity (DC)		Minimum Meter Accuracy (all values are +/-)		Other Requirements
Up to 10 kW, using non-automated reporting Meters used as part of a Data Acquisition System (“DAS”) must meet the "Greater than 10 kW and up to 1 MW" nameplate capacity requirements below.		2% (ANSI C-12.1-2008 )		Electromechanical meters may be used. Refurbished meters, if retested and certified, may be used. Allowable configurations for meters are : Single-phase 120 volt - Form 1S, Class 100 Single-phase 240 volt - Form 2S, Class 200 Three-phase 120 - 480 volt - Form 14- 16S, Class 200
Greater than 10 kW and up to 1 MW		1% (ANSI C12.16 or better)		Only new solid state meters are allowed. Current transformers (“CTs”) must conform to the 0.6% (ANSI/IEEE C57.13-2008) accuracy class, or the meter must be tested using the CT and certified to meet the minimum accuracy requirement.
Greater than 1 MW		0.5% (ANSI C12.20-2010)		Only new meters are allowed. CTs must conform to the 0.3% (ANSI/IEEE C57.13-2008) accuracy class.

Meter Testing and Calibration

Meters shall be tested, and as needed calibrated or replaced, in accordance with Table 2 below.

Meter Testing Requirements
Category (kW – DC)	Minimum Frequency	Other Requirements
Up to 10 kW	None	MassCEC at its discretion may require testing or replacement of a meter associated with unreasonable energy production reports.
Greater than 10 kW and up to 500 kW.	As required by DAS Vendor requirements and best practices	DAS Vendors are required to demonstrate energy reports to the PTS are within +/- 1% of the meter registry for an individual system. MassCEC at its discretion may require testing or replacement of meter associated with unreasonable energy logged by the meter registry.
Greater than 500 kW	At least once every two years per NEPOOL OP18	Only new meters are allowed. CTs must conform to the 0.3% (ANSI/IEEE C57.13-2008) accuracy class.

 

Solar Meter Placement

The solar PV production meter may be installed at any point between the AC output of an inverter and the point of interconnection with the electric grid.

As an alternative, energy reported from a utility owned net-meter installed on the utility side of the electric service may be used in lieu of a solar production meter where:

• the output from a solar PV inverter is interconnected on the utility side of the electric service
• as long as the PV array is the only generator or energy storage system behind the utility net meter.

Treatment of Parasitic Load

Per the Renewable Energy Portfolio Standard (RPS) 225 Code of Massachusetts Regulations (CMR) 14.02, energy consumed by parasitic load, which is not otherwise accounted for by the solar PV production meter, must be excluded from reported generation values.

For the purposes of SREC II metering requirements, unaccounted for parasitic load is defined as the tare loss associated with nighttime energy consumption by an inverter. Tare loss of less than or equal to the levels listed below (as reported by the inverter manufacturer) is deemed to be de minimis and is not required to be excluded from the meter reading.  When bi-directional (net) meters are used to report production the value reported shall be the “delivered” energy, not the “net” energy.

Inverter Rated Output (AC)	Tare Loss de minimis Level (Watts)
10 kW or less	30
Greater than 10 kW up to 100 kW	330
Greater than 100 kW up to 1 MW	3,330
Greater Than 1 MW	8,200

If the tare losses of an individual inverter exceed the de minimis levels contact MassCEC for further guidance on reporting.

Multiple Inverter Systems

Multiple inverter systems which combine output power from the multiple inverters before interconnecting to the gird, and which are registered in the PTS as a single PV system, shall have only one meter that measures the combined energy output.

Meter Labeling

PV system meters shall have weather resistant labeling that clearly associates the meter with the PV system. For example “PV Production Meter.”

Meter Start

All new and refurbished meters shall be set at 000000 or 999999 at time of shipment to the installer to ensure accurate and consistent “start” readings for every system.

Meter Warranty

A meter warranty of not less than one year is required on all new and refurbished meters.