A Simple Guide to Solar Revenue Grade Meters

Solar Revenue Grade Meters (RGMS) are meters that meet the American National Standards Institute Standard (ANSI). Revenue Grade Meters measure solar power production (DC output). ANSI certified meters record solar yield with an uncertainty of less than +/-0.5%. For this reason, incentive reporting agencies and PPAs widely favor ANSI certified meters. The data recorded by these meters is especially useful in providing reliable production readings to calculate the potential loss.  

Why do I need an RGM? …

Solar Power Incentive Reporting, Including RECS

Perhaps the most common use for RGMs is reporting production to incentive programs like RECs (Renewable Energy Credit). The ANSI certification is a guarantee that the reading is accurate and can be relied upon. Most performance-based incentive (PBI) programs require that the production reported was measured by an RGM. If a solar plant is in a state with a PBI, a solar installer will install an RGM that is approved to report for the incentive program specific to that location.

Solar Data Systems offers approved solar performance meters for automatic incentive reporting in the following states:  California, Connecticut, Illinois, Massachusetts, Maryland, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Washington, D.C. 

For products approved in your market, contact us.

Ensure over-all health of the system

Although some inverters now have a revenue grade meter option, many do not. In those cases, the reading from the inverter will not meet the accuracy requirements to be ANSI certified. In our 10 years in the solar industry, we have seen inverters register values deviating as much as 20-25% from the actual metered PV output. Below is an example showing a site that has four 15kW inverters, a maximum output of 60kWp. However, the inverters reported a peak of 83kW. A plant of this size can not produce that much. The inverter indicated a much higher production value than what was actually produced. 

The production reading from an RGM can be compared to the expected power output determined by the yield forecast. If the production reading determines that the forecast has not been met, it is possible that there is an issue occurring with the solar power plant.

RGM Production Reading Compared to Yield Forecast

Confirm the Need for a Truck roll

Have you ever sent a crew out to the site, only to confirm that the issue you were looking for was not actually there? An RGM provides a dependable reading for analyzing solar power production issues.

Recently, the Solar Data Systems team performed an analysis on a customer’s solar plant and detected a complete drop in production at the site. Fortunately, this customer had installed a revenue grade meter on this plant. Our team was able to use the data from the RGM to confirm the validity of the inverter data. The charts below compare the inverter data to the RGM reading on June 6^th versus June 7^th, 2020. The production loss started on June 7^th and continued through June 29^th. In total, the loss was 88,850 kWh, equivalent to $10,662, based on the electricity rate in the area. The data provided by the RGM confirmed the need for a truck roll in order to avoid a larger, negative financial impact.

Example: RGM reading confirms solar inverter power production on June 6, 2020

Total Estimated Financial Loss = $10,662

Example: RGM reading confirms solar inverter is not producing power on June 7, 2020

Avoid Unnecessary Truck rolls

What’s better than confirming the need for a truck roll? Avoiding an unnecessary one.

RGM’s can confirm the existence of solar power production, even in the event that the inverter is not reporting any. In the example below, inverter #7 experienced a communication issue. According to the inverter data displayed on the monitoring platform, inverter #7 was not producing any power. Fortunately, this solar plant was also fitted with an RGM. A simple comparison of the RGM production reading to the inverter reading at the same day and time proved that inverter #7 was in fact producing power. The O&M provider concluded that this was not a production issue, but a communication issue, which did not warrant an immediate visit to the site.

Truck Roll Avoided = $125 Savings

Example: Inverter #7 not communicating. RGM confirms inverter production.

Retrofit Existing Sites with Monitoring

Do you have a site with obsolete or non-existent monitoring? Do you have a site connected to 3G which might be affected by the sunset date of various carrier as of next year?

Solar Data Systems offers solutions from Solar-Log® that are compatible with over 100 inverter brands, making it easy to monitor first-generation plants that were often installed without monitoring. However, even with this extensive compatibility, it is possible that retrofitting inverter-direct monitoring is not a possibility at certain locations. When that occurs, installers can rely on easy-to-retrofit RGM solutions. RGMs will not provide granular data for advanced analysis, but they can tell the O&M provider if a system is producing and how much. This data can be used to detect sudden drops, but also for gradual losses that occur over the lifetime of the array.

Precise Billing

All project stakeholders benefit from the accuracy provided by solar revenue grade meters, especially when billing is involved and based on solar production. Service providers are often required to provide investors with regular reports on the amount of power being generated by the array. When a performance guarantee is in place, meaning a contract states that the solar plant will generate a minimum financial return, the accuracy of the production meter is crucial.

Accurate Usage Monitoring

Consumption, or usage monitoring is a valuable, inexpensive tool that is over looked by many installers and/or plant owners. An RGM can measure how much energy the building or individual circuits are using. It provides a way to detect an increase or change in the plant owner’s usage after the plant has been installed. We see it often, customers go solar and as soon as they do, they change the way they use electricity, ultimately increasing usage. To the installer or contractor who guarantees certain savings, this knowledge is the difference between gaining or losing customer confidence and referral business. Building owners can make adjustments and lower electricity costs once they understand how the self-produced energy is used. Reducing peak demand charges and lowering the amount of power purchased from the grid equals a savings far greater than the initial hardware expense.

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Solar Revenue Grade Meters from Solar Data Systems

Solar Data Systems has many options for revenue grade meters and below is a quick summary of the benefits of each solution. We can help you identify the best solution for the next project. Contact us for a quote.

Solar Data Systems ArrayMeter

We understand how important it is to have a reliable solar production meter that is also quick to install. The all-new ArrayMeter is a revenue grade meter that is plug and play and easy to install. This ANSI-certified meter is accurate enough to meet or exceed SREC or PPA requirements.

Automatic performance-based incentive reporting (PBI/SREC) is available with the use of the ArrayMeter.

*GATS/PTS, NEPOOL reporting currently available. Others coming soon.

Solar-Log 2050 Commercial Revenue Grade Meter

The Solar-Log 2050 is a revenue grade meter assembly for commercial and industrial-scale solar plants. The assembly provides highly accurate solar plant production metering required by many PPAs, financing companies, and performance-based incentive programs (PBI/SREC). When combined with a Solar-Log® data logger, the assembly offers performance data from inverter direct monitoring and optional power control.

Solar-Log 350LAN

The Solar-Log 350 LAN provides revenue grade metering for solar PV plants in locations where cell service is weak or unavailable. The LAN connection increases the number of times data is transferred per day, leading to near real time visualization of plant data for system owners and installers. This plug and play socket meter is compatible with all residential solar PV plants up to 48kW. Approved in most SREC and PBI markets, this accurate meter provides a solution for hassle-free, automatic incentive reporting.