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Frequently Asked Questions

  1. What types of CSI data are available on California Solar Statistics?
  2. How does California Solar Statistics make this solar program data available to Web site users?
  3. How often is the data updated?
  4. Is the capacity rating on California Solar Statistics measured in AC or DC megawatts?
  5. What are some of the factors that impact application processing times?
  6. What do tilt, azimuth and tracking mean related to solar PV systems?

Data Resources and Methodology

  1. Cost Caps: Systems < 10 kW CEC-AC = $6.48; Systems ≥10 kW CEC-AC = $5.88
  2. California Leads the Nation
  3. Consumer Price Index (CPI)
  4. Cost per Watt
  5. 95th Percentile Methodology
  6. Reported System Costs ($/watt)

Definitions of Statuses and Terms

  1. Working Data Sets
  2. Raw Data Sets
  3. "Pending" and "Installed" Applications

Frequently Asked Questions

What types of CSI data are available on California Solar Statistics?

When CSI participants apply for incentives with the program, they provide data about their residence or business and about the solar system they are installing. California Solar Statistics chooses among those many application data fields the items expected to be of greatest interest to the public. California Solar Statistics then "cleans" the "Raw Data Set" which is now the "Working Data Set". California Solar Statistics reports on data in the Working Data Set available on the website. In the future, the CSS site may include other types of data in addition to CSI application data, such as interconnection data or data from other solar programs.

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How does California Solar Statistics make this solar program data available to Web site users?

The data can be accessed in a number of ways. Users of California Solar Statistics can:

  1. Download the complete working data set
  2. Search the program data by specific fields
  3. Download the filtered data used to create a figure (at the bottom of any figure in the View Solar Statistics menu)

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How often is the data updated?

The data is updated every Wednesday evening.

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Is the capacity rating on California Solar Statistics measured in AC or DC megawatts?

Unless noted otherwise, capacity is reported in California Solar Statistics as "CEC-AC" megawatts. The CEC-AC rating standards are based upon 1,000 Watt/m² solar irradiance, 20 degree Celsius ambient temperature, and 1 meter/second wind speed. The CEC-AC Watt rating is lower than the Nameplate rating at Standard Test Conditions (STC).

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What are some of the factors that impact application processing times?

The factors affecting processing times that are outside of the PAs' control include, but are not limited to:

Factors that impact the time to grant a reservation request:
-Missing energy efficiency audit documentation
-Missing signature(s) on contract(s)
-Missing or incomplete documentation
-Applicants that are slow to respond or do not respond

Factors that impact the time to process an Incentive Claim Form:
-System not interconnected
-Revised EPBB not submitted to reflect changes in installed equipment
-Missing PMRS documentation
-Missing or incomplete documentation
-Missing Field Verification Certification Form
-Missing, late, or incorrect submittal of monthly PBI data

Also, high volume application spikes around step changes have a significant impact on processing times.

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What do tilt, azimuth and tracking mean related to solar PV systems?

Two factors which determine the production of a solar PV system are the tilt and azimuth of the solar array. The tilt of a solar array is its angle relative to the ground whereas the azimuth of a solar array is its compass direction relative to true north (as distinguished from magnetic north). A tracking system allows a solar array to change its tilt, azimuth, or both to optimize production.

A tilt of zero degrees would represent a panel lying flat on the ground, whereas a tilt of 90 degrees would represent a vertical solar array. Typically, to optimize solar production, a solar array’s tilt should be close to the location’s latitude. For example, a fixed solar array in Los Angeles (with a latitude of 34.05 degrees north) would have its optimal tilt around 34 degrees. An azimuth of 180 degrees indicates an array pointed true south whereas an azimuth of 270 degrees indicates an array pointed to the west, etc. While many factors affect how a project’s tilt and azimuth are selected, theoretically an array with its tilt close to its latitude facing true south would optimize solar production.

In the downloadable Working Data Set, "CSI Project Tilt" and "CSI Project Azimuth" are listed for every project where data are available. If there are multiple arrays for a given project and they have the same tilt or azimuth, the system’s tilt and/or azimuth will be listed. However, if there are multiple arrays with multiple tilts and/or azimuths the word "Multiple" will be listed.

For the "Tracking Type" column, if the project is a single- or dual-axis tracking system it will be so indicated. If it includes a mixture of tracking and fixed array systems, "Mixed" will be listed.

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Data Resources and Methodology

Cost Cap Methodology

Separate "Cost Caps" are calculated for two size categories: systems up to 10 kW CEC-AC and systems 10 kW and greater. For each of these size categories, the cost cap calculation is based on the cost per watt for Host Customer owned projects completed within the last 12 months, where cost per watt is defined as the (total cost) divided by the (CEC-AC system size) for each project. The simple average of all cost per watt values for these projects is determined, and a $1.00 adder is applied to that value. The "Cost Caps" are then defined as:

(12 month mean) + ($1.00) = Cost Cap for Host Customer Owned Systems <10 kW CEC-AC

(12 month mean) + ($1.00) = Cost Cap for Host Customer Owned Systems ≥10 kW CEC-AC

which are currently

($5.48) + ($1.00) = $6.48 (<10 kW)

($4.88) + ($1.00) = $5.88 (≥10 kW)

Projects whose cost per watt exceed these values will be required by the Program Administrators to submit a 'High Cost Justification and Acknowledgment Form' before their incentive will be approved, as per section 3.4.5 of the CSI Program Handbook. All CSI systems are subject to the cost caps, regardless of system ownership structure.

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California Leads the Nation

On the GoSolar California homepage, as well as on the California Solar Statistics front page, you will find several statistics in a box entitled "California Leads the Nation." The first two data fields, "Solar Projects" and "MW Installed" are statewide values, with data sourced as follows:

The data values regarding cost, "Avg cost/watt <10kW" and "Avg cost/watt >10kW", are taken from the CSI General Market program data set ONLY, as it is the only data set with complete cost and sizing information on a per-project basis. For each of the two size categories (<10kW and >10kW, using the sizing definition found here), the values are calculated with the following parameters:

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Consumer Price Index (CPI)

CPI Source
Where indicated, some cost values on the California Solar Statistics site are modified using a Consumer Price Index (CPI), specifically the California CPI found on the California Department of Finance site:

Months with No Data
The spreadsheet listed above provides exact data for every other month, and interpolates between the surrounding months for months with no exact data. For example, data in the spreadsheet is provided for February and April, but not for March. The CPI for March = [(February + April) / 2].

In all cases, dollars are normalized to the current quarter, so that ${today} = [(CPI{currentQuarter} / CPI{Quarter}) * ${Quarter}]. For example, assuming the current quarter is February 2010:

Treatment of Quarters
For the purposes of calculation on this site, quarterly values based on the middle month of each quarter are used, including the interpolation for dataless months described above. For example, the Q3 2009 value is the August 2009 value, and the Q2 2009 value is the [(April 2009 + June 2009) / 2] value.

Quarterly Grouping
When CPI is applied to project costs, the CPI from the Reserved quarter is used. The Reserved quarter is defined as the quarter which contains the earliest of the "First Confirmed Reservation Date", the "First Reservation Reserved Date", or the "First Pending RFP" date.

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Cost per Watt

Cost per Watt information throughout this site is presented only for "Completed" applications. "Completed" applications are applications which are currently in the PBI - In Payment or Completed statuses. This extended definition of "Completed" is meant to include PBI projects, which will remain in PBI - In Payment status for 5 years after the incentive has been approved and payment has begun.

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95th Percentile Methodology

Percentiles are used to compare one value in a data set to all other values; they give a good idea of how one value compares to the rest of a set.

For example, if 10 days is the 95th percentile of application processing times, only 5% of applications take 10 days or more to process.

To calculate a percentile, the data are first arranged in numerical order and given a rank between 1 and N, where N is the number of total data points in the set.

The percentile being calculated is then given a rank to match a data point in the set. The following equation is used to calculate the rank of a given percentile, where n is the rank given to the Pth percentile, out of a list of N data points.

n = P/100 x N +0.5

n is rounded to the nearest integer

For example, for a set of 1000 data points, the rank of the 95th percentile is 951. The 95th percentile would correspond with the 951st data point. It can be concluded for this example that, at most, 5% of the set is greater than the 951st value.

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Reported System Costs ($/watt)

The current $/watt data available for California Solar Initiative projects present difficulties when comparing host customer-owned and third-party-owned systems (e.g. leases or power purchase agreements (PPAs)). The reported costs for host customer-owned systems are simple, as they reflect the purchase price inclusive of parts, labor, permitting fees, overhead, and profit. Third-party-owned systems, on the other hand, are reported in a variety of ways, and may also capture costs for additional services.

There are at least three different ways third-party owners are reporting their system costs:

1. If the third-party owner buys the system from a contractor, the third-party owner may report that sale price as the system price to the CSI Program. This value, however, does not include the overhead and profit of the third-party owner, which are actually passed through to the host customer.

2. Alternatively, the third-party owner may report the "Fair Market Value" (FMV) of the system, a figure reported in tax filings. FMV is an estimate of the market value of a property, based on what a knowledgeable, willing, and unpressured buyer would probably pay in an arm's-length transaction.

3. Lastly, the third-party owner may report the appraised sum of cost inputs.

In addition, most third-party-owned systems also include the cost of inverter replacements, and some even include roofing replacements - services not typically included in the price of a host customer-owned system.

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Data Archive Definitions

Working Data Sets

The Working Data Sets show all publicly available data fields, after the data has been filtered for errors, for current applications to the California Solar Initiative. To make the Working Data Set, California Solar Statistics performs a series of data integrity filters on the Raw Data Sets to remove any application with data errors, such as a data field outside acceptable ranges. The data removed due to errors are reviewed (and fixed) regularly by Program Administrators. The Working Data Set also removes all projects which have not yet reached Reservation Request Review status. The Working Data Set is the data used for all figures and tables throughout the California Solar Statistics website, and the filtering improves the quality of the information. The Working Data Set is recommended for use by external parties. Definitions of data fields found in the Working Data Set can be found here:

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Raw Data Sets

The Raw Data Sets show all publicly available data fields, before the data has been filtered for errors, for current applications to the California Solar Initiative. The Raw Data Sets (previously sometimes called the Public Data Export) contain data from all applications submitted to date, exported from the California Solar Initiative's application database (PowerClerk) each week. This represents the data exactly as it was in PowerClerk at the time of export. No applications, including those with critical data errors, have been removed from this file. Definitions of data fields found in the Raw Data Sets can be found here: The Raw Data Sets are not recommended for use by external parties as they may contain severe data entry errors.

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What is the difference between pending and installed applications?

As an application is processed it goes through different statuses. These are described in the Applications status definitions link shown above. Pending applications are considered to be those between the "Reservation Request Review" and "Confirmed" statuses, and Installed applications are considered to be those between the "Incentive Claim Request Review" and the "Completed" statuses. Not all "installed" projects have completed their CSI application processing; some installed projects are awaiting inspection or payment, and some are awaiting payment over a five-year period.

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