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Home > Worldwide PV Report > Market & Policy

Solar PV Buying Decision Made Easy

We have good policy. We have low(er) prices. By focusing on more consistent consumer education tools, we have the potential to better organize demand which drives faster adoption of distribute solar energy systems. This, in turn, can lead to reducing current industry over-supply conditions. One way to do this is with a Solar Energy Estimate (SEE) Report to help consumers compare residential solar PV system performance through ‘MPG-Like’ report.

By Doug Payne



The Solar Energy Estimate (SEE) Report is an open web service at SolarHub.com. The goal is to reduce consumer confusion by offering a service similar to the Federal government’s new-car MPG rating system. The SEE Report has the potential to reduce consumer confusion when purchasing a solar PV system. Our next challenge will be to educate consumers and drive industry adoption.

NREL estimates for customer acquisition costs for your typical 5 kW system currently represent up to US$0.20/Wp due to consumer confusion about system performance, difficulties in comparing multiple bids, and prolonged decision making. We have integrated our ‘Performance and Finance Initiatives’ to reduce these costs by 20% annually through standardized quotation templates, uniform financing contracts, and related checklists that support this goal. The combined Performance and Finance toolkits eliminate hidden expenses and risk through delays and lost sales due to a lack of clarity. Our vision is low risk, low cost, high speed PV process.

The SEE Report is another in a series of accomplishments to reduce balance of system and soft costs by 20% annually through standardized templates, uniform financing contracts, checklists and other process streamlining best practices.

The one page SEE report uses standardized calculations combined with the installer’s site-specific equipment design variables and local solar insolation data to provide the annual estimated energy production for the solar system. This standardized estimate allows consumers to compare multiple solar PV designs for a specific location. In addition to the underlying calculations (based on NREL’s PVWatts, v2 and California CSI EPBB derate factors), it offers a standardized report format, modeled on the MPG window sticker, enabling consumers to find the data of interest for comparing quotes and building consumer confidence. The SEE report includes estimates for the first year energy production; the total energy produced over 25 years and a graphic showing the variation in monthly energy production over a full year. “We are pleased to have our SEE report vision launched and ready to serve consumers and solar installers,” said Tim Keating, SolarTech Performance Committee Chair and VP of Marketing & Field Operations at Skyline Solar. “The SEE Report has the potential to reduce consumer confusion when purchasing a solar PV system. Our next challenge will be to educate consumers and drive industry adoption.”


SolarNexus, an active participant in the Performance Committee and Co-Developer of SolarHub, developed the SEE Report software to satisfy the Performance Committee’s documented requirements. SolarHub proved to be a natural home for the SEE Report. SolarHub is a free web-based source for product specifications on thousands of solar products providing a cost-reducing resource to solar contractors. “We are pleased to be supporting SolarTech’s mission to lower balance of system soft costs,” said Eric Alderman, President and CEO of SolarNexus. “We look forward to working with SolarTech to drive adoption with consumers to make asking for their SEE Report as natural and expected as asking for a car’s MPG rating.”

Key to maximizing the SEE Report’s benefit is the broad adoption by commercial solar sales professionals and proposal tool providers such as OnGrid Solar. “OnGrid envisions the SEE Report as a natural complement to its quotation tool suite,” said Andy Black, CEO, OnGrid Solar. “We look forward to actively supporting SolarTech’s mission to drive down acquisition costs. This consumer confidence building tool is long overdue,” continued Andy. “We have taught thousands of new solar professionals through our Solar Sales and Marketing classes. The SEE Report is a right tool at the right time to ensure ethical selling and satisfied consumers leading to long term industry growth.”



Why Are We Offering This?


Consumer purchases are often confusing. Technology, products and services change at a rapid pace, which is difficult to keep up with. Thanks to the internet, many services have evolved to support consumers from web sites maintained by specialty consumer advocacy groups to general services such as AAA ratings. Residential Solar Photovoltaic (PV) systems bring in additional level of complexity to consumers due to the often custom design nature of the product. These complexities can lead to consumer buying confusion, which then can lead to lost sales opportunities for an industry and economy that badly needs growth. These buying confusions were first described in a study issued by SolarTech in 2010, which can be located on our web site. SolarTech (an industry non-profit trade association) seeks to provide a consumer service to enable faster and more informed consumer buying decisions through its collaborative industry solutions process, and thus enable the growth of the industry for all.

The SEE Report is envisioned by SolarTech to enable consumer in their solar PV buying decision by providing an independent third party assurance of expected base-line performance. This base level performance report can then be used as a reference point by the consumer to enable comparison of quotations from multiple solar installation firms and/or vendors.

Multiple analogies can be leveraged to describe what the SEE report is and how it should be used by consumers. The traditional Good Housekeeping Seal of Approval, Consumer Reports, Energy Star ratings, and AAA are but a few examples that serve consumers. The best analogous model that most closely relates to the SEE Report is the Federal EPA’s Miles per Gallon rating system illustrated in the following figure.

Consumers are familiar with how to use this rating system in new car purchase decisions as well as the standard disclaimer, ‘your mileage may vary’. Thus in technical terminology, this is a relative standard of comparison to a standard test suite, and not intended to be an absolute guarantee of mileage expectations. There are too many local variables and drive habits to provide an absolute guarantee. However, as a consumer you can compare several car models with the sticker price and your individual requirements. By enabling a transparent exchange of information, the consumer is better informed, and the overall industry is more vibrant and successful.

For Solar PV interested consumers, the SEE report provides five very basic features:

1. Simple and standardized report format enabling consumers to find the estimated energy production quickly and reliably see the following illustration and include the following energy estimates:

   a. Annual energy production

   b. 25 year energy production

   c. Graphical summary of the monthly change in energy production due to the position of the sun and the effect of shading;

2. Standardized calculations for energy production estimates based on well know and accepted industry standards;

3. Web access directly to the consumer, or through the solar sales person as part of a standard quotation process;

4. Summary of all key solar inputs to provide clarity when comparing between alternative designs.


The SEE Report ISN’T:

1. A guarantee of energy performance at your location;

2. A replacement for commercially available quotation tools used by your solar sales representative. 

The SEE Report should be viewed as another tool to enable easier buying decisions. Just like ‘Consumer Reports’ or other third-party consumer information services supporting buying decisions for various product and services. A commercial solar PV proposal tool may produce a different production estimate than the SEE Report, and that’s okay. The SEE Report should be within 10% of any other legitimate calculation, and the reputable solar sales person should be able to discuss and explain the differences between the proposal and the SEE Report to the consumer’s satisfaction. The consumer should then be able to use the SEE Report to compare multiple solar system proposals.


How Does It Work?


The key to the SEE Report is standardization of many elements that impact solar energy estimation. The SEE Report works by using the same industry standard calculation engine every time, and by simplifying the input assumptions and variables for the calculations to just the most important basic ‘few’. The calculation engine is PVWatts 2 developed and distributed by the National Renewable Energy Laboratory in Golden, Colorado. It is a common solar PV calculation resource in the solar industry and is readily available from www.nrel.gov/rredc/pvwatts. As such it makes an ideal standard ‘ruler’ by which to base all comparisons in simple residential solar systems.

The next critical element is the standardizing of the process and the input variables and assumptions that are passed to PVWatts. This is controlled by a neutral third-party web site called SolarHub (www.solarhub.com). SolarHub was created in 2009 in a partnership of SolarTech, Solar Nexus and Solar Pro to provide a single source of component information for solar PV designers. The vast majority of commercially available solar modules and inverters can be found in SolarHub for design comparison assistance. All manufacturers have access to their product data to facilitate maintaining the most current certified information. SolarHub also updates its records based on the California Energy Commission listing of certified solar products as well as the SANDIA database.

The SEE Report is currently launched as a web service from within SolarHub in order to control consistency and transparency. The SEE Report utility collects the basic site specific information, combined with some standard defaults, and passes this information to PVWatts calculator engine. PVWatts returns the calculation result which is presented as a PDF formatted report to the end user.

 The SEE Report web services interface is fully documented to allow for seamless integration into any solar quotation tool as an option for consumer proposals. The SEE Report can also be accessed directly by consumers at SolarHub’s website.


Site Specific Variables and Equipment under User Control


Site Address:

-Mounting method (governing air flow and cooling in inches off the roof)

-Array azimuth (in degrees true North)

-Array tilt (in degrees from horizontal)

-Percent monthly shading estimates for all twelve months

-Number of solar PV modules, manufacturer and model

-Number of solar PV inverters, manufacturer and model

The SEE Report tool allows the user to select the appropriate manufacturer module and inverter from the SolarHub data base. The name-plate power ratings are derated 5% (i.e. 95% of published value) before submission to PVWatts as per accepted practice by the California Energy Commission for the EPBB calculator on the CSI web site (www.csi-epdd.com). Exceptions are allowed for modules where the manufacturer has specified the derating value. Both the SEE Report and the California EPBB calculator use PVWatts as the calculation engine. Thus in those cases where the calculations follow the standard CEC derating practice, then the production estimates derived from EPBB should agree with the SEE Report. The SEE Report also uses the same methodology to calculate the effect of the mounting method that the California EPBB calculator uses.

The SEE Report offers the additional advantage of a standardized and simplified consumer friendly report format with applicability in other States. The final calculation assumptions are clearly noted in the PV System Specification section of the final PDF formatted SEE Report.


Sales Professional Friendly Parameters


The report allows the sales person to include the following in each report: company name, company logo, contact name, contact phone number, contact email.


Default Parameters Fixed for Simplification


Energy losses naturally occur in various parts of a solar installation. The SEE Report accounts for these losses with the following industry standard parameters: 

-Mismatch = 98% (Accounts for slight variation in the output of each solar panel)

-Diodes and connections = 99%

-DC Wiring = 98%

-AC Wiring = 99%

-Soiling = 95%

-System Availability = 98%

Overall system derating of 87.6% is a product of all derating factors above. If these factors were not included in an estimate consistently, the end results could vary by up to 12.4%. The advantage of the SEE Report is to eliminate this potential variation and allow consumers to compare estimates on apples to apples basis.

The SEE Report is suitable ONLY for single plane arrays for both rooftop and ground mount in reasonably dust free locations. For multi-plane arrays resulting from sections of the PV array mounted on different roof faces, a separate calculation should be performed for each section.

The SEE report assumes various standard inputs across all designs so the actual energy production will vary from this estimate. For example, locations subject to high dust and soiling are likely to have lower energy production than estimated, however this will likely effect all designs equally. The SEE report provides a consistent basis to discuss the performance of a system. Where there are innovative design elements that the SEE report does not account for, this is an opportunity for the solar installer to communicate the benefit of those design choices starting from a consistent reference point provide by the SEE report.


A Non-Profit Industry Association


SolarTech is a non-profit industry association focused on removing the institutional process barriers to the growth of the solar PV industry. Improving process barriers include things such as streamlined permitting and utility interconnection processes; best practices, standards and training for rapid, quality and safe installations; simplifying and clarifying performance specifications, and working with the financial industry to improve the financing options for consumers. SolarTech works through member-led subcommittees such as the Performance Committee which lead the development of the SEE Report tool.

SolarTech has sponsored two university research projects into the various public domain solar PV calculators, which are available on SolarTech’s web site. Through industry conversation first started at SolarTech’s 2010 Summit, followed by SolarTech’s Performance Symposium at InterSolar 2010, and culminating in a final consensus in the 2011 SolarTech Summit it became clear that a consumer facing tool and standard was a solution that could benefit consumers and the industry.

SolarTech and the industry magazine SolarPro magazine had previously worked with SolarNexus to develop and market SolarHub, a third-party resource for solar PV design information. SolarNexus is an active participant in the Performance Committee, and they implemented the SEE Report project requirements into SolarHub at SolarTech’s request. Thanks to the generous support of Pacific Gas & Electricity and the California Energy Commission, the project was funded and began development in July 2011. The public release took place on October 17, 2011. After more than two years of vision and dedication by numerous individuals and SolarTech member companies, the SEE Report is a reality. Expanding the usage of the SEE Report throughout the industry is a key goal moving forward.


Doug Payne is Co-Founder and Executive Director of SolarTech (www.solartech.org). Prior to being appointed as SolarTech’s first Executive Director, Payne led the Commercial Business Development Division of Real Goods Solar, serving Northern and Central California. Payne has nearly 20 years of engineering, program, and business management experience. Payne’s solar inspiration came 20 years ago as a member of Canada’s inaugural entry in the 1990 World Solar Challenge, a solar car race across Australia. He holds a B.S. degree in Mechanical Engineering from Queen’s University, Ontario, Canada.




 For more information, please send your e-mails to pved@infothe.com.

2011 www.interpv.net All rights reserved.


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