Organizations that deploy solar PV systems and battery energy storage systems usually do so for many reasons including sustainability goals and demonstrating environmental stewardship. However, the chief reason for adopting solar and battery solutions is often anticipated energy cost savings. Given these economic drivers, it is important to remember that much like any investment, energy systems require effective organizational management and control.

A common question posed to commercial enterprises and public agencies that have solar PV systems or Battery Energy Storage Systems on their properties is, “Are the systems at your sites providing the savings that were originally projected”. Unfortunately, most organizations are unable to respond to this question with any certainty.

To address this, TerraVerde Energy provides clients with detailed reporting on their solar and energy storage systems, giving them full transparency into system performance and the financial impacts that these systems have on their bottom line.

TerraVerde Energy’s Asset Management division provides clients with dedicated performance monitoring, preventive maintenance, revenue program management, and detailed operational & financial reporting which all work together to optimize the performance of systems and provide transparency into the overall operations of a client’s energy systems.

TerraVerde Energy recently published an article celebrating $50M of savings that we have delivered to our clients and we are pleased to now share how we calculate savings for our clients and what goes into this analysis.

TerraVerde’s Approach Analyzing Solar & Battery Savings

Our approach to these analyses begins with the collection, cleaning, and the curation of several data sets, including:

Electric Utility Information

  • Interval data from the electric utility meter
  • Monthly bills from the electric utility provider
  • Bill determinates from the applicable electric utility rate schedules
  • Tariff details for the applicable utility programs (e.g., NEM)

Solar & Battery Information

  • Interval data of the historical solar PV energy production
  • Interval data for the charge & discharge cycles from the battery energy storage system
  • Project contracts (including project cost and performance guarantee details)

To support the effort of collecting, analyzing, and reporting on these various data set, TerraVerde has developed a proprietary software platform called SolarShadow. In addition to supporting our system performance monitoring and performance issue management efforts, SolarShadow enables our Asset Management team to establish direct data connections to utility meter, solar meter, and battery meter information.

SolarShadow connects directly to customer utility, solar, and battery meter data

Our Asset Management team maintains an electricity rate database which forms the basis of our energy project savings analysis. This rate database is structured to enable real-time updates to each billing determinate that is a part of each applicable utility rate schedule. For example, PG&E’s E-19 rate (a common rate schedule for medium to high energy use commercial customers), has 62 different rate structure variables including (among other items) transmission charges, distribution charges, generation charges, and demand charges.

SolarShadow manages each billing determinate of retail rate schedules

Each time an electric utility updates their rate schedule, SolarShadow is updated to reflect these revised  rates, enabling us to provide simulated bills that are accurate to the penny.

We perform a rigorous quality check (QC) process for each data set that we process, then triage / repair individual data sets as needed, then test to certify completeness and accuracy. Once we have ensured that the data passes the initial review test, we load the data into SolarShadow where each 15-minute interval data for usage (kWh) and demand (kW) is labeled with the associated time-of-use period (e.g., Summer Peak). Subsequently, the 15-minute interval data are bucketed (i.e., grouped and summed) into their respective time-of-use periods within each billing cycle. We then compare the result of bucketed values against the actual bills collected from the utility to validate the energy and demand values, and most importantly, the invoiced amount. This QC process ensures we have collected the correct data and our model baseline is calibrated correctly. It is important to note that we often find discrepancies which lead us to identify meter reading mistakes, billing oversights, and solar & battery performance reporting bugs.

Additionally, we collect the following contracts and documents so we can conduct necessary validation on utility and solar & battery provider billing (as applicable):

  • Interconnection Agreements to determine the tariff under which the system is operating (i.e., Net Energy Metering (NEM), NEM-Aggregation, RES-BCT, etc.)
  • Project contracts, invoices, and exhibits for performance guarantee terms, as-built installation drawings and modeled production values, and other terms and conditions

Armed with these data sets, project documents, and SolarShadow we then model the “ex-solar/battery” usage profile of the facility (i.e., what they usage would have been had the solar and / or battery system not been deployed at that site). Using this modeled ex-solar/battery facility energy usage profile, and the curated rate database in SolarShadow, we then simulate what each monthly electricity bill would have been had the solar and / or battery system not been deployed, using the otherwise applicable rate schedules and tariffs.

Sections From An Example TerraVerde Solar & Battery Report

Finally, to calculate the actual solar / battery program savings, we subtract the post-solar/battery costs from the ex-solar/battery costs as shown in the following table:

Billing Scenario # Scenario Name
1 Annual facility electricity bill (ex-solar/battery) under the applicable rates and tariff
2 Annual facility electricity bill (post-solar/battery) as provided by the utility + solar / battery project expenses (energy payments, asset management costs, etc.)
3 Annual savings: Billing Scenario 1 – Billing Scenario 2

If your organization is seeking ways to improve performance and have clear insight into system financial savings, you need TerraVerde Energy in your corner.  Our team of dedicated energy engineers and business professionals are ready to help you effectively manage your solar PV and battery energy storage systems and deliver comprehensive reporting in brief and easy to understand formats.  Support from TerraVerde Energy will give you transparency into your systems to answer with confidence the next time someone asks you about the operational and financial status of your energy systems. To learn more, write to us at hello@terraverde.energy.

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