Distribution Grid Integration Unit Cost Database

This database contains unit cost information for different components that may be used to integrate distributed PV onto distribution systems. The total cost of implementing different upgrades on a given system is influenced by the number of units required. This is system specific. Additionally, the efficacy of different solutions to mitigate distribution impacts and expand the hosting capacity varies significantly, and thus unit costs should not be generally compared to determine the cost-effectiveness of different upgrade options. Instead, these unit costs should be combined with an engineering analysis of a specific system to understand which upgrades and how many units of each are required to accommodate different levels of distributed PV. Examples of how NREL is using this data to estimate total costs on different feeders is included below.

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.

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.  

Some data relates to technologies at an earlier stage than others. In particular, Distributed Energy Management Systems (DERMS) is an emerging technology which currently has no standard definition or functionality. Cost vary substantially depending on the project specifics, existing infrastructure (e.g. communications and enterprise systems) of the utility, the functionality included, and the number of DER being managed. This also varies by vendor, and not all vendors or DERMS functionalities are represented in our database. Finally, there may be some costs associated with DERMS that are not captured here including, for example, the cost of training utility engineers on how to operate the DERMS or any overhead costs associated with re-organization. These can be a substantial portion of cost in some scenarios, but would decrease after the first deployment with a given utility.

Even for more mature technologies, some may undergo innovation to reduce cost. Unit costs in this database are only intended to be representative estimates for a given location or vendor for the date specified.

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.

Organization of Each Page

In order to make this database more machine readable, we have implemented a common structure for each sheet. This structure is as follows:

• Row 1: Sheet title
• Row 2: Blank
• Row 3: Field names/header
• Remaining rows: Data entries

New cost breakdown data have not been added since the previously release of the database; they have only been moved to a separate file titled ‘Cost_breakdown_data_2018.xlsx.’

We include the units for upgrade parameters in the field name (e.g. ‘voltage’ is now ‘voltage_kV’ for voltage regulators).

Dollar Years and Inflation

All costs in the database are in the same dollar year as the date listed. For example, if the date field says ‘2014,’ the costs are in 2014 USD. For analysis or comparison of unit costs, all data should be converted into a common dollar year by adjusting for inflation as needed. 

Low-, Mid-, and, High-Cost Numbers in the Database

In some of the sheets, an entry (row) in the database may have a low-, mid-, and high-cost number associated with it. These represent the range of costs from the specific data source associated with that entry or row, not the range of costs for that type of upgrade generally (e.g. across the United States or all data collected). For the tabs where some sources provided a range and others provided only a single data point, the single data points are categorized as mid.

However, these cost ranges do not capture the full range of costs that might be observed for any given scenario.

Data Gaps and Needs

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.