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Distribution Grid Integration Unit Cost Database

NREL's Distribution Grid Integration Unit Cost Database contains unit cost information for different components that may be used to integrated distributed solar photovoltaics (PV) onto distribution systems. The database is focused on hardware and software costs, and contains more than 335 data points from a variety of utilities, PV developers, technology vendors, and published research reports.

The goal of the database is to provide a useful, curated, and transparent source of information for assessing distribution grid integration costs associated with PV. It includes information from the California utility unit cost guides on traditional system upgrades that could be used to mitigate any impacts, as well as additional information on costs associated with advanced solutions including distributed energy management systems, communications infrastructure, and energy storage.

Examples of ways this database could be used by different parties include:

  • PV developers: Developing estimates of interconnection costs for specific PV systems
  • Analysts: Improving estimates of costs to integrate PV into the power system
  • Utilities: Comparing their costs to other utility costs and obtaining additional data about unit costs for emerging solutions that they might not already have access to.

ACCESS THE DATABASE

Guide to the Database

This database contains unit cost information for different components that may be used to integrate distributed PV onto distribution systems. Which components are required, and how many of each, is system-specific and should be determined by analyzing the effects of distributed PV at a given penetration level on the circuit of interest in combination with engineering assessments on the efficacy of different solutions to increase the ability of the circuit to host additional PV as desired. The current state of the distribution system should always be considered in these types of analysis.

The data in this database was collected from a variety of utilities, PV developers, technology vendors, and published research reports. Where possible, we have included information on the source of each data point and relevant notes. In some cases where data provided is sensitive or proprietary, we were not able to specify the source, but provide other information that may be useful to the user (e.g., year, location where equipment was installed). NREL has carefully reviewed these sources prior to inclusion in this database.

The database includes information on the categories of upgrades listed in the table below. The specified party/parties who provided the data correspond to those groups that originated the cost estimate, not necessarily the group from which NREL received the data. For example, data pulled from PV interconnection reports obtained from PV developers is still labeled as utility-sourced data, since the utility rather than the developer came up with the cost numbers in the interconnection reports. Some high-level notes on data sources and data quality are provided here. Additional notes on specific data points are included within the database itself.

Category Primary Data Sources Data Quality Notes
Voltage regulators Utilities: publicly available utility cost guides, SGIP reports 3 data sources, with data from 2014 and 2016. Some missing data on regulator current ratings.
Capacitor banks Utilities: publicly available cost data from utilities, PV interconnection reports. Range of hardware only costs from a technology vendor are also available. 8 data sources, with data from 2011, 2015, and 2016. Some missing data on capacitor specifications.
Transformers Utilities: publicly available utility cost guides, project reports, and PV interconnection reports 8 data sources, large number of data points. Some specifications missing, but detailed specifications are available for most entries. Data from 2005-2017.
Reclosers and relays Utilities: publicly available utility cost guides and PV interconnection reports 8 data sources, large number of data points for a variety of recloser/switch types.
Protection upgrades (e.g., direct transfer trip [DTT], zero sequence voltage [3V0]) Utilities: PV interconnection reports 6 data sources. Large number of data points on 3V0 and DTT from PV interconnection reports. Also some data on other substation fault protection upgrades; in some cases unit/component costs could not be disaggregated
Phase balancing Utilities: PV interconnection reports Limited: only two data points
Voltage regulating device control modifications Utilities: publicly available utility cost guides and PV interconnection reports; some data on controller hardware only from technology vendors  
Removal and relocation of existing voltage regulation equipment

Utilities: publicly available utility cost guides and PV interconnection reports

In some cases, utilities reported moving or removing voltage regulating devices as part of the mitigation strategy. 3 data sources from 2011 to 2016.
Conductor/re-conductoring

Utilities: publicly available utility cost guides and PV interconnection reports

4 data sources from 2016. Specific cable types/part numbers specified for some data points, for others only overhead or underground and sometimes location (rural or urban) is provided.
Energy storage

Lazard and Greentech Media

2 data sources from December 2016 and 2017. Includes total installed cost data for a range of storage technologies and system types.
Communications equipment and sensors Technology vendors, utilities: publicly available utility cost guides, EPRI Most data from 2016. Includes unit costs for different communications components (e.g., gateways for field devices, communication bridges). Just one data point with range of communication network infrastructure costs. Infrastructure costs will depend significantly on the type of system used (e.g., fiber optic, wireless, radio) and the existing utility communication infrastructure.
D-SVC, D-STATCOM, and power regulators Technology vendors, utilities: PV interconnection reports Very limited data, only 3 data points. More data will be added as available for these emerging technology solutions.
Advanced metering infrastructure (AMI) EPRI, the Edison Foundation 2 data sources, both from 2011.
SCADA, DMS, DERMS systems Technology vendors, utilities: PV interconnection reports Data sources from 2012 to 2017 (most from 2016 and 2017). In some cases, costs were back calculated or estimated from reports. Most data is on DERMs or SCADA. DERMs functionality varies across vendors.
Primary service and metering Utilities: publicly available utility cost guides and PV interconnection reports 4 data sources from 2015 and 2016. Data on specifications (e.g., voltage of connection) is missing for some sources.
O&M and component lifetimes Technology vendors, tax guidelines, private consulting companies, IEEE Some data is provided to give a sense of the order of magnitude of the lifetime differences between different technology classes only. Extreme caution is required when using any of this data, as O&M and component lifetime data is sparse, the effects of PV on device O&M and lifetimes is not well known or documented, and O&M and lifetimes can vary significantly even without the presence of PV due to differences in operating conditions (e.g., temperature, humidity, loading). In some cases, data represents only the useful life determined previously for tax purposes.
Advanced inverters Inverter manufacturers, PV developers The cost of advanced inverters depends on whether the capability of inverters as installed (e.g., if a retrofit of the inverter is required to obtain desired functionality versus just a setting change, which could be performed remotely). We include several different scenarios in the database, but there is some uncertainty around these costs.

This database is focused on hardware and software costs. Soft costs (e.g., permitting, interconnection studies) and other overhead costs are not included and should be accounted for separate in any analysis. Additional engineering costs may also be incurred, depending on the scenario, and thoughtful construction of analysis cases/scenarios is always required to obtain results representative of costs that could be observed in practice.

While future work collecting additional data and further vetting of data provided by different stakeholders will improve the database in the future, we hope that this will provide a useful source of information for assessing distribution grid integration costs associated with PV.

We are using this data at NREL to conduct bottom-up analysis of costs that might be incurred on distribution systems to integrate high penetrations of PV under a variety of technology scenarios. We are using an iterative hosting capacity approach for this analysis, and considering both steady-state/static and quasi-static time series power flow cases. 
We are seeking additional data on any components related to integration of PV onto distribution systems to include in this database. In particular, we are seeking additional data on:
  • Data operations and maintenance (O&M) costs and component lifetimes for different components, and how the presence of PV affects these values
  • Data on software and distributed energy management system costs
  • D-SVC, D-STATCOM, and power regulators
  • Communications and sensing equipment
  • Experiences with advanced inverter costs (new inverters, retrofits, enabling existing features)
  • Advanced metering infrastructure (AMI)

If you are willing to share any data on these components, please contact Kelsey.Horowitz@nrel.gov. We are accepting data on total installed costs of any component in addition to data on specific cost components (e.g., hardware-only costs). As discussed above, we are able to include data in the database in an aggregated and/or anonymized way if preferred in order to ensure protection of confidential, business sensitive, or proprietary information, and are open to signing nondisclosure agreements as necessary. Our team has earned the trust of our industry partners over the course of years of collecting and handling sensitive information related to PV component and system costs. 

This research is supported by the Energy Department's Solar Energy Technologies Office.

Contact

Kelsey Horowitz

Research Engineer

Kelsey.Horowitz@nrel.gov | 303-275-4347