Details for: 4217-E (Part 1 of 1).pdf

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Gary A. Stern, Ph.D.
Managing Director, State Regulatory Operations

May 21, 2020
(U 338-E)

Proposed Reporting Methodology to Monitor the Frequency
and Amount of Voltage Excursion Events Pursuant to
Resolutions E-4898 and E-5016

Southern California Edison (SCE) hereby submits for approval by the California Public
Utilities Commission (CPUC or Commission) a proposed methodology to collect and
report on data that informs of the number and duration of voltage excursion events. This
reported data will be used to estimate the impact on customers with inverter-based
distributed energy resources (DER) interconnected with the electrical distribution grid.
Within the Rule 21 proceeding (Rulemaking 11-09-011) the Commission adopted
Decision (D.)16-06-052 that, in part, required SCE, Pacific Gas and Electric Company
(PG&E), and San Diego Gas & Electric Company (SDG&E) – collectively the investorowned utilities (IOUs) – to submit a Tier 3 advice letter (AL) with proposed revisions to
Rule 21 to set forth technical requirements and effective dates for Phase 3 advanced
inverter functions.1 SCE submitted Advice 3647-E on August 18, 2017, which included a
proposed date after which the technical requirements associated with smart inverter
Phase 2 communications and Phase 3 advanced functions would need to be activated
on newly interconnected DER systems.
On April 26, 2018, the Commission adopted Resolution E-4898 that incorporated the
eight Phase 3 advanced functions recommended by the Smart Inverter Working Group

D.16-06-052, Alternate Decision Instituting Cost Certainty, Granting Joint Motions to
Approve Proposed Revisions to Electric Tariff Rule 21, and Providing Smart Inverter
Development a Pathway Forward for Pacific Gas and Electric Company, Southern
California Edison Company, and San Diego Gas & Electric Company, Ordering Paragraph
(OP) 9.

P.O. Box 800

8631 Rush Street

Rosemead, California 91770

(626) 302-9645

Fax (626) 302-6396


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ADVICE 4217-E (U 338-E) -2- May 21, 2020 (SIWG). The resolution established an effective date for Function 6 Volt-Watt mode2 of nine months following approval of a SunSpec Alliance Communication Protocol Certification Test Standard.3 On May 22, 2018, SunSpec Alliance issued its Communication Protocol Certification Test Standard. Function 6 was therefore activated nine months later on February 22, 2019. In Resolution E-4898 the Commission found that the impact of Function 6 activation was expected to be de minimis while the benefits to the electric distribution grid could be realized. The Commission stated: The Volt Watt Mode function will simply respond to these voltage events and keep the grid safe. The Volt Watt Mode function will facilitate higher penetration of DERs because it is the DERs interacting in a cumulative fashion (with everchanging load conditions) that can cause system voltage excursions.4 The Commission further stated: If the activation of Function 6 is harmful to a particular system owner, it will only be because the voltage levels on the circuit are regularly outside acceptable Rule 2 limits.5 Finding that Function 6 was warranted and valuable, the Commission in Resolution E-4898 directed the IOUs to 1) work with stakeholders to develop standardized reporting methodologies to monitor the frequency and amount of voltage excursions and 2) in consultation with the Commission’s Energy Division, each submit a Tier 1 Advice Letter on the proposed methodologies by October 1, 2018. On October 1, 2018, the IOUs submitted Tier 1 ALs with their proposal for standardized reporting methodologies to monitor the frequency and amount of voltage excursions.6 The IOUs proposed the following process: • 2 3 4 5 6 Utilize each IOU’s respective voltage complaint process to help monitor the frequency and amount of voltage excursions experienced by DER customers who have installed a smart inverter with the Volt-Watt function activated. The function modifies active power from DERs based on predetermined voltage ranges to prevent the local voltage on the distribution circuit from rising/dropping outside of allowable levels. A letter from Edward Randolph, Director of the CPUC’s Energy Division dated July 11, 2018, clarified that February 22, 2019 was the effective date for Function 6. Resolution E-4898, p. 27. Ibid. PG&E AL 5395-E, SCE AL 3872-E, and SDG&E AL 3283-E.
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ADVICE 4217-E (U 338-E) • • • • -3- May 21, 2020 Monitor the voltage excursions by estimating the amount of energy reduction due to the activation of the Volt-Watt function. Identify and report on voltage issues caused on the utility side of the meter. Utilize Advanced Meter Infrastructure (AMI) data in conjunction with PVWatts®7 production curves to estimate DER curtailment. Perform an energy loss calculation when the results of the investigation would reveal that the voltage issues were due to the customer’s equipment for no more than 20 customers per year. Sunrun, Inc. (Sunrun) and the Interstate Renewable Energy Council, Inc. (IREC) protested the IOUs’ advice letters on October 22, 2018. Sunrun represented that the IOUs’ advice letters were missing detail regarding how the IOUs would proactively monitor, collect, report on, and respond to voltage excursions from AMI data. IREC voiced that the proposed methodologies lacked sufficient detail to ensure that the appropriate voltage data is obtained in compliance with Resolution E-4898. SCE replied to IREC’s protest on October 29, 2018. The IOUs’ advice letters were suspended and escalated to Tier 3, requiring Commission action. On December 19, 2019, the Commission adopted Resolution E-5016 (Resolution) that denied the IOUs’ advice letters and proposed methodologies. SIWG MEETING OVERVIEW The Resolution required the IOUs to hold at least two SIWG meetings that addressed at a minimum the following: • • • If PV Watts or other modeling PV tool/profile is best suited; Alternative proposed methodologies (large IOUs, IREC, NREL or others); and What AMI data and capabilities are available to determine PV power curtailment, more specificity on the amount of data that would need to be processed under different monitoring approaches, and the feasibility and costs involved in using alarms and/or alerts in lieu of widespread data processing.8 The IOUs held four meetings with the SIWG beginning January 23 and ending March 19, 2020. In addition, the IOUs held multiple separate conference calls with NREL and with IREC and Sunrun. An overview and summary of these meetings is provided in Appendix A. SCE also provides greater detail on the specific discussions related to each of these three topics below. 7 8 PV Watts is an online interactive tool that estimates the energy production and cost of energy of grid-connected photovoltaic (PV) energy systems throughout the world. It allows homeowners, small building owners, installers and manufacturers to easily develop estimates of the performance of potential PV installations. See Resolution at Ordering Paragraph (OP) 2.
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ADVICE 4217-E (U 338-E) -4- May 21, 2020 DISCUSSION The Resolution directed the IOUs to discuss several issues both within the SIWG and in the resulting advice letters, including (1) available modeling tools, (2) alternate proposed methodologies, and (3) the IOUs’ AMI capabilities. SCE provides this information below. The proposed methodology resulting from these discussions is set forth in the following section. PV Output Profiles Discussed With the SIWG On January 23, 2020, SIWG stakeholders (IOUs and others) evaluated various PV modeling tools and profiles that could be utilized within the energy loss estimation methodology. To assist with the evaluation, SCE presented in graphical form three applicable PV output profiles: 1) PVWatts® generated profile based on typical installation parameters; 2) Typical clear day PV output profile based on historical performance data; and 3) NREL proposed PV output profile that, although not realistic, provides a simplified profile that can be used for estimating energy losses with adequate precision. This graphical representation is shown in Figure #1 (Prominent PV Production Profiles).
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ADVICE 4217-E (U 338-E) Figure 1. Prominent PV Production Profiles -5- May 21, 2020
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ADVICE 4217-E (U 338-E) -6- May 21, 2020 Evaluation of Proposed PV Output Estimation Methodologies The SIWG considered various energy loss methodologies that could be employed in the IOUs’ energy loss estimation calculations. Three main energy loss calculation methodologies were discussed: 1. The energy loss methodology proposed in the IOUs’ October 1, 2018 Advice Letters based on PVWatts® as the PV output data source; 2. The energy loss methodology proposed in the IOUs’ October 1, 2018 Advice Letters but using a typical clear day PV profile; and 3. The energy loss methodology developed by NREL (NREL Method #1), which uses a maximum PV output profile from 9am to 3pm and zero output for the remainder of the hours. To assist in the discussion, SCE presented Figure #2 (Energy Loss Estimation Methods) to compare calculations from all three methods. Below SCE discusses the pros and cons of each proposed method. PVWatts®: As SCE explained in the SIWG meetings, a potential negative aspect of a PVWatts® generated PV profile is that in some cases it could lead to energy loss estimation inaccuracies due to the PVWatts® predicting PV output intermittency that may not actually occur as shown in Figure #1 (Prominent PV Production Profiles). In these cases, using PVWatts® could result in lower energy loss estimates than what would happen under real world system operating conditions. An advantage of using PVWatts® to derive PV production profiles is that the tool is publicly accessible and allows customers to generate these profiles if desired. Moreover, the PV profiles may be generated based on location-specific customer provided information (such as project type, installation angle and zone within the service territory), which may increase the accuracy of the energy loss estimation. PVWatts® Using a Typical Clear Day PV Profile: The utilization of typical clear day PV output profiles may lead to inaccuracies in the energy loss estimations. This is because the profile assumes all clear days in the year, which leads to maximum PV output every day of the year. In fact, not all days in the year are clear and there will be days when it is cloudy and PV production will be significantly reduced or will have a high level of intermittency. Another potential drawback related to utilization of typical clear day profile is that it would increase the complexity of the energy loss estimation as compared to using NREL Method #1. A potential advantage of this method is that it could provide a common profile for all utilities.
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ADVICE 4217-E (U 338-E) -7- May 21, 2020 NREL Method #1: SCE understands the NREL Method #1 proposed profile could yield values that contain a potential level of inaccuracy given that the NREL-proposed PV output profile is not reflective of normal PV output characteristics. Therefore, in some cases, NREL Method #1 may lead to lower or higher energy estimate values depending on the PV system’s specific characteristics. The potential advantages of NREL Method #1 are its simplicity and that it can be used within an energy loss estimation methodology without complexity.
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ADVICE 4217-E (U 338-E) Figure #2 – Energy Loss Estimation Methods -8- May 21, 2020
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ADVICE 4217-E (U 338-E) -9- May 21, 2020 Recognizing that the methodology estimation methods discussed above all inherently involve a level of uncertainty due to estimation assumptions, the SIWG discussed which method would be the most appropriate accounting for the complexity and accuracy associated with each method. SCE presented Figure #3 (Comparative Results) to the SWIG to aid in the discussion reflecting a comparison of energy loss method estimations assuming a representative AMI meter voltage profile as shown in Figure #4 (Representative AMI hourly voltage profile). As shown in Figure #3 (Comparative Results), the estimated energy loss values from each method are generally similar to each other and within the margin of error. The SIWG concurred that all three methods could yield a similar energy loss estimation. Therefore, the SIWG determined that the simplest method (NREL Method #1) along with NREL PV profile was the most appropriate given its simplicity of calculation while yielding an appropriate level of estimation accuracy.
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ADVICE 4217-E (U 338-E) Figure #3 – Comparative Results - 10 - May 21, 2020
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ADVICE 4217-E (U 338-E) Figure #4 – Representative AMI hourly voltage profile - 11 - May 21, 2020
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ADVICE 4217-E (U 338-E) - 12 - May 21, 2020 In addition to the three alternative methods described above, NREL presented other approaches using a combination of planning tools, feeder characteristics, irradiance data, AMI meter data and inverter manufacturer data. However, given the complexity of these methods, the need to create new complex tools, and the need for additional engineering resources, SIWG stakeholders did not want to pursue any of these other methods and no further discussion was held on this topic. AMI Voltage Data Capabilities and Constraints To promote transparency, the Resolution ordered SCE to specify in this advice letter what AMI data is available (i.e. instantaneous, average, minimum/maximum) and whether it has the same data available as the other IOUs, or what data is available for the different customer classes. The Resolution also directed SCE to include within this advice letter more specificity on AMI data and monitoring methodologies available, and how alarms and/or alerts could be set up to notify SCE of voltage excursions. On February 6, 2020, the SIWG engaged in the discussion related to IOU AMI capabilities. The purpose of this meeting was for each utility to explain its AMI capabilities, available AMI data, and types of AMI data. The IOU presentations revealed that there are differences in AMI data among the three IOUs. As discussed during the February 6 meeting, SCE’s AMI system has three meter category types to serve different classes of customers: 1) ITR1-Single Phase; 2) ITR3 – Basic polyphaser; and 3) ITR4- Advanced Polyphase. Each of these meters records and reports hourly voltage values for maximum, minimum, and average over each hour interval. This information is depicted in Figure #5 (SCE AMI Voltage Measurement and Reporting Capabilities).
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ADVICE 4217-E (U 338-E) - 13 - Figure #5 – SCE AMI Voltage Measurement and Reporting Capabilities May 21, 2020
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ADVICE 4217-E (U 338-E) - 14 - May 21, 2020 During the February 6, 2020 meeting, SCE discussed with the SIWG that while SCE AMI meters have alarming and/or alerting capabilities that could be set up to notify SCE of voltage excursions, SCE did not believe it was necessary for SCE to activate these alarm functions in order to support voltage measurement reporting. As SCE explained, SCE currently collects daily voltage data that could be further utilized to detect voltage abnormalities without the need to activate additional alarming. SCE did not receive any feedback from SIWG stakeholders that AMI alarming functions were necessary to support voltage abnormalities and therefore SCE no longer considered the activation of these alarming functions. As discussed above, although SCE currently receives daily AMI data, this data can only be accessed manually on a case by case basis for purposes of energy loss estimation. SCE does not currently have the capabilities to analyze the collected data to perform the energy loss estimations in an automated fashion. In accordance with the Resolution’s requirements, SCE evaluated the cost for developing a tool to be able to extract, evaluate, and analyze the AMI data for energy loss estimation purposes. SCE estimates that it would cost approximately $200,000, along with ongoing operating and maintenance costs to support the tool. At this point, SCE does not believe this expense and use of resources is necessary given the expected de minimis energy loss resulting from enabling the volt/watt function. In addition, SCE discussed with the SIWG that while SCE AMI meter daily records hourly maximum, hourly minimum, and hourly average voltage data, SCE would be using the hourly average data for its energy loss estimation. SCE did not receive any objections from the SIWG members.
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ADVICE 4217-E (U 338-E) Figure #6 – SCE AMI Metering Alarming Capabilities - 15 - May 21, 2020
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ADVICE 4217-E (U 338-E) - 16 - May 21, 2020 PROPOSED CURTAILMENT ESTIMATION METHODOLOGY SCE’s proposed methodology is identical to the methodology proposed by SDG&E and PG&E. The proposed methodology is based on collaboration with SIWG stakeholders and discussions with IREC and Sunrun. The IOUs discussed the methodology below with SIWG stakeholders at the March 19 SIWG meeting. Stakeholders did not raise objections to the majority of the eight steps proposed below; however, one stakeholder stated that additional internal review was required on certain items (namely, 3.d and 7). However, this stakeholder provided no additional feedback following the conclusion of the SIWG discussions. In regards to step 2.c, only one stakeholder commented against implementing this step. Below is the eight-step process proposed: Consensus Step Activity 1 The IOU voltage complaint process will be the basis for voltage Yes reporting to satisfy CPUC requirements. 2 The IOUs will provide curtailment calculations for volt/wattenabled customers in the voltage complaint process with voltage readings over 106% of nominal voltage with the following characteristics: Yes a. Include calculations for all utility-caused, customerreported issues per reporting period. Yes b. Report on up to 20 of the first customer-caused and reported issues on an annual basis. No c. When the event duration is less than 48 hours, it will be considered a limited anomaly and will not be reported. 3 IOUs will use the NREL Method 1 process using currently available AMI data to calculate estimated curtailment utilizing the following processes for estimation calculation: Yes a. Voltage intervals of 1-hour for residential or 15minute for commercial as available Yes b. Average voltage readings utilized over the voltage interval for SDG&E/SCE and instantaneous voltage readings for PG&E based on existing capabilities Yes c. NREL Method 1 is only being approved for generalized/anonymous reporting but not for potential individual customer claims Yes d. For 3-phase service points, the average voltage per phase will be used for curtailment estimation
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ADVICE 4217-E (U 338-E) 4 5 6 7 e. Any missing or removed data due to data quality will be removed from numerator and denominator of % curtailment calculations Report will provide yearly % energy loss calculation using the previous 12 months of the available voltage data per customer* Report will provide 1 month % energy loss calculations using the previous 30 days of data as available per customer* Report will provide the utility mitigation used in the voltage complaint process or indicate if the reported complaint was a customer created issue Report will summarize the customer curtailment studies by the number of customers with curtailment estimates in the following buckets: a) ≤ 2%, b) 8 - 17 - May 21, 2020 Yes Yes Yes Yes Yes 2% ≤ 4%, c) >4% Provide voltage histogram for % of total hours in volt/watt curtailment range (>106%) for the worst case customer with energy loss > 5%. Yes * Will use available data within these date ranges from data stored in centralized AMI databases (PG&E/SCE) or the limit of meter memory (SDG&E). The yearly and 30-day reports are triggered when the voltage complaint is received. No cost information is required for this advice letter. This advice letter will not increase any rate or charge, cause the withdrawal of service, or conflict with any other schedule or rule. TIER DESIGNATION Pursuant to General Order (GO) 96-B, Energy Industry Rule 5.1, this advice letter is submitted with a Tier 1 designation. EFFECTIVE DATE SCE respectfully requests that this advice letter become effective May 21, 2020, the date submitted.
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ADVICE 4217-E (U 338-E) - 18 - May 21, 2020 NOTICE Anyone wishing to protest this advice letter may do so by letter via U.S. Mail, facsimile, or electronically, any of which must be received no later than 20 days after the date of this advice letter. Protests should be submitted to: CPUC, Energy Division Attention: Tariff Unit 505 Van Ness Avenue San Francisco, California 94102 E-mail: Copies should also be mailed to the attention of the Director, Energy Division, Room 4004 (same address above). In addition, protests and all other correspondence regarding this advice letter should also be sent by letter and transmitted via facsimile or electronically to the attention of: Gary A. Stern, Ph.D. Managing Director, State Regulatory Operations Southern California Edison Company 8631 Rush Street Rosemead, California 91770 Telephone (626) 302-9645 Facsimile: (626) 302-6396 E-mail: Laura Genao Managing Director, State Regulatory Affairs c/o Karyn Gansecki Southern California Edison Company 601 Van Ness Avenue, Suite 2030 San Francisco, California 94102 Facsimile: (415) 929-5544 E-mail: There are no restrictions on who may submit a protest, but the protest shall set forth specifically the grounds upon which it is based and must be received by the deadline shown above. In accordance with General Rule 4 of GO 96-B, SCE is serving copies of this advice letter to the interested parties shown on the attached GO 96-B and R.11-09-011 and R.17-07-007 service lists. Address change requests to the GO 96-B service list should be directed by electronic mail to or at (626) 302-3719. For changes to all other service lists, please contact the Commission’s Process Office at (415) 703-2021 or by electronic mail at
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ADVICE 4217-E (U 338-E) - 19 - May 21, 2020 Further, in accordance with Public Utilities Code Section 491, notice to the public is hereby given by submitting and keeping the advice letter at SCE’s corporate headquarters. To view other SCE advice letters submitted with the Commission, log on to SCE’s web site at For questions, please contact Mary Brown at (626) 302-8103 or by electronic mail at Southern California Edison Company /s/ Gary A. Stern Gary A. Stern, Ph.D. GAS:mb:cm Enclosures
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ADVICE LETTER SUMMARY ENERGY UTILITY MUST BE COMPLETED BY UTILITY (Attach additional pages as needed) Company name/CPUC Utility No.: Southern California Edison Company (U 338-E) Utility type: ELC GAS PLC HEAT ELC = Electric PLC = Pipeline WATER Contact Person: Darrah Morgan Phone #: (626) 302-2086 E-mail: E-mail Disposition Notice to: EXPLANATION OF UTILITY TYPE GAS = Gas WATER = Water HEAT = Heat (Date Submitted / Received Stamp by CPUC) Tier Designation: 1 Advice Letter (AL) #: 4217-E Subject of AL: Proposed Reporting Methodology to Monitor the Frequency and Amount of Voltage Excursion Events Pursuant to Resolutions E-4898 and E-5016 Keywords (choose from CPUC listing): Compliance AL Type: Monthly Quarterly Annual One-Time Other: If AL submitted in compliance with a Commission order, indicate relevant Decision/Resolution #: Resolutions E-4898 and E-5016 Does AL replace a withdrawn or rejected AL? If so, identify the prior AL: Summarize differences between the AL and the prior withdrawn or rejected AL: Confidential treatment requested? Yes No If yes, specification of confidential information: Confidential information will be made available to appropriate parties who execute a nondisclosure agreement. Name and contact information to request nondisclosure agreement/ access to confidential information: Resolution required? Yes No Requested effective date: 5/21/20 No. of tariff sheets: -0- Estimated system annual revenue effect (%): Estimated system average rate effect (%): When rates are affected by AL, include attachment in AL showing average rate effects on customer classes (residential, small commercial, large C/I, agricultural, lighting). Tariff schedules affected: None Service affected and changes proposed1: Pending advice letters that revise the same tariff sheets: None 1 Discuss in AL if more space is needed. Clear Form
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Protests and all other correspondence regarding this AL are due no later than 20 days after the date of this submittal, unless otherwise authorized by the Commission, and shall be sent to: CPUC, Energy Division Attention: Tariff Unit 505 Van Ness Avenue San Francisco, CA 94102 Email: Name: Gary A. Stern, Ph.D. Title: Managing Director, State Regulatory Operations Utility Name: Southern California Edison Company Address: 8631 Rush Street City: Rosemead Zip: 91770 State: California Telephone (xxx) xxx-xxxx: (626) 302-9645 Facsimile (xxx) xxx-xxxx: (626) 302-6396 Email: Name: Laura Genao c/o Karyn Gansecki Title: Managing Director, State Regulatory Affairs Utility Name: Southern California Edison Company Address: 601 Van Ness Avenue, Suite 2030 City: San Francisco State: California Zip: 94102 Telephone (xxx) xxx-xxxx: Facsimile (xxx) xxx-xxxx: (415) 929-5544 Email: Clear Form
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ENERGY Advice Letter Keywords Affiliate Direct Access Preliminary Statement Agreements Disconnect Service Procurement Agriculture ECAC / Energy Cost Adjustment Qualifying Facility Avoided Cost EOR / Enhanced Oil Recovery Rebates Balancing Account Energy Charge Refunds Baseline Energy Efficiency Reliability Bilingual Establish Service Re-MAT/Bio-MAT Billings Expand Service Area Revenue Allocation Bioenergy Forms Rule 21 Brokerage Fees Franchise Fee / User Tax Rules CARE G.O. 131-D Section 851 CPUC Reimbursement Fee GRC / General Rate Case Self Generation Capacity Hazardous Waste Service Area Map Cogeneration Increase Rates Service Outage Compliance Interruptible Service Solar Conditions of Service Interutility Transportation Standby Service Connection LIEE / Low-Income Energy Efficiency Storage Conservation LIRA / Low-Income Ratepayer Assistance Street Lights Consolidate Tariffs Late Payment Charge Surcharges Contracts Line Extensions Tariffs Core Memorandum Account Taxes Credit Metered Energy Efficiency Text Changes Curtailable Service Metering Transformer Customer Charge Customer Owned Generation Mobile Home Parks Name Change Transition Cost Transmission Lines Decrease Rates Non-Core Transportation Electrification Demand Charge Non-firm Service Contracts Transportation Rates Demand Side Fund Nuclear Undergrounding Demand Side Management Oil Pipelines Voltage Discount Demand Side Response PBR / Performance Based Ratemaking Wind Power Deposits Portfolio Withdrawal of Service Depreciation Power Lines Clear Form
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Appendix A
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Appendix A Summary of SIWG Meetings The IOUs held four meetings with the SIWG, beginning January 23 and ending March 19, 2020. In addition, the IOUs held multiple separate conference calls with NREL and with IREC and Sunrun. An overview of these meetings is provided below. December 30 - Outside SIWG Meeting: Meeting occurred with NREL and SCE. The purpose of this meeting was for SCE to gain a greater understanding of the NREL energy loss methodologies. January 9 - Outside SIWG Meeting: Meeting held between NREL and IOUs and centered upon discussions surrounding available methods and tools for estimating DER curtailment in response to voltage excursion events with Function 6 Volt-Watt mode activated. January 17 – Outside SIWG Meeting: Meeting with IREC, Sunrun and IOUs with discussions regarding areas of the IOU Advice Letter filings and related protests that should be focused upon for SIWG discussions. SIWG Meeting 1 – January 23: SCE and NREL presented various energy loss estimation methodologies including a comparison of the following three methods: • IOU energy loss methodology as proposed in the October 1, 2018 AL which relied on PVWatts® as the PV output data source; • IOU energy loss methodology as proposed in the October 1, 2018 AL but using a typical clear day PV profile; • Energy loss methodology developed by NREL (method #1), which uses a maximum PV output profile from 9am to 3pm and zero output for the remainder of the hours. The discussion found that that the three energy loss estimation methodologies yield approximately the same estimated energy loss values. It was shown that NREL’s simplified curtailment calculation produced the highest estimated curtailment but was easy to implement. SIWG Meeting 2 – February 6: Each IOU gave presentations on the capabilities and limitations of their AMI systems. There was some discussion of the manufacturers providing voltage data to the IOUs to assist in vetting voltage violations since the voltage at the inverter terminals is a known value. SIWG Meeting 3 – February 20: This meeting was focused on discussing the upcoming IOU advice letters and reporting along with confirming if prior outstanding issues and concerns had been resolved. Stakeholders in this meeting appeared to coalesce around the NREL simplified curtailment calculation (NREL method #1). Stakeholders also discussed the customer complaint process and what potential enhancements could be
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made, including manufacturers directly submitting a complaint to each utility’s customer complaint process on behalf of the customer. March 4 - Outside SIWG Meeting: The IOUs met with IREC and Sunrun to walk through the IOU proposal for the May advice letter filing. PG&E shared a presentation that summarized the process at a high level. The meeting focused on trying to confirm the areas of consensus and address the points of disagreement. March 11 - Outside SIWG Meeting: The IOUs met again with IREC and Sunrun to walk through all eight points, identifying where there was consensus and where there was disagreement. Proposals to resolve the disagreements were discussed with the understanding that this process would be presented at the upcoming fourth SIWG meeting. SIWG Meeting 4 – March 19: The IOUs presented the outline of their proposed methodologies and reporting approach to stakeholders.
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