Factors Effecting Photovoltaic System Performance

solar-on-pole-mountA variety of factors influence the performance of photovoltaic system production.   System owners want to get the most for their money when they install solar panels on their home or business.

Location, location, location

One of the most important factors in system performance is the location of the solar array.  Location has three important components:

  1. Array azimuth (orientation with respect to true south)
  2. Array tilt (orientation with respect to horizontal) and
  3. Shading.

Array Orientation
In southwest Ohio we want the solar array to face south.  The sun rises in the east and sets in the west and peaks in the sky at solar noon each day.  While it is possible to mount modules facing east, west or even north the performance penalty increases the further away from true south the array faces.   For rooftop mounting on pitched roofs the best approach is to mount the modules parallel to the roof.  This provides the best aesthetics, though it does compromise performance to the extent that the roof does not face true south.    For flat roof applications there is opportunity to orient the modules irrespective of building orientation, and a variety of commercial mounting systems make this an easy approach.  So how much does array orientation effect system performance? To view the graph comparing system performance vs. array orientation click on the following link.

Figure 1- System Performance vs. Array Orientation

The chart shows that if the array faces south + 30 degrees it will still produce 97-98% of the optimal system output.  In Figure 1, 90 degrees represents an east facing array and 270 degrees represents a west facing array.  As you can see from the chart these extremes reduce the array performance by almost 20%.  So south facing arrays work best but if that does not match your roof line there are other options with predictable outcomes.

Array Tilt
A photovoltaic module works best when the sun strikes it at a 90 degree angle.  Most residential and small commercial solar arrays are installed with a fixed tilt (more on tracking arrays later).  Since the angle of the sun (as measured from the horizon) changes throughout the year, what is the best angle to mount the modules to maximize system performance?  Assuming we have an array which faces true south the following chart provides the answer (for southwest Ohio).  To see the graph thaat compares tilt and system performance, click on the following link.

Figure 2 – System Performance vs. Array Tilt Angle

The chart shows that for our area, 30 degrees is the nominal tilt angle for a photovoltaic array.  If we mounted the array horizontal to the ground or flat we would still achieve 88% of the optimal production and if we mounted the array vertically facing south we would achieve only 58% of our optimal production.   Most pitched roofs range from 18 – 45 degrees and these will achieve 95+% of optimal system output.  Again for flat roofs the mounting systems allow us to select the angle of tilt for the modules.

Tracking Arrays
There are mechanical solar tracking systems available that attach to the panels and track the sun throughout the day to maximize the hours of sunlight.  In general these systems add mechanical complexity (read installation and maintenance cost) which in general outweigh the performance improvements.  Trackers are typically only being implemented for large utility scale projects.  SunRock recently installed a pole mounted system which orients the array to face south and has a hand crank that is turned to adjust the array tilt to follow the seasons.  This system improves system performance by approximately 5% annually with no expected increase in maintenance costs.

Photovoltaic modules are very sensitive to shading.  SunRock performs a shading analysis for each site during the project evaluation and bid preparation.  This allows us to provide an accurate estimate of the system’s expected performance.   Shading occurs from surrounding trees, buildings, chimneys, dormers, and other structures, so a careful evaluation of the site needs to be performed prior to estimating production data.

If you have a yard full of trees and a roof full of shade, then your rooftop may not be a good candidate for solar.  There are other options though.  Solar panels can be installed on ground mounts, top of pole mounts, carport structures, etc.  For some possibilities check out our project photos.

There are also new micro-inverter and DC optimizers which can help mitigate shading issues at the site. These are deployed based upon specific shading issues at the site.

PV Systems Increase your Home’s Value

solar-panel-on-farmBerkeley National Laboratory just released a report entitled “An Analysis of the Effects of Residential Photovoltaic Energy Systems on Home Sale Prices in California.”    The study was funded by the US Department of Energy.  The main focus of the study was to determine whether homes with installed PV systems sold for more money than comparable homes without PV.  The authors studied 72,000 homes in California of which 2000 had PV systems installed when they were sold.

The research found that homes with PV systems in California have sold for a premium compared to homes without PV.  When the sale prices were compared to the size of the PV systems installed, the average home sale price was $5.5/Watt with a range of $3.9 to $6.4/Watt.  This is higher than the homeowner’s original investment on the installation which averaged $5/Watt from 2001 to 2009 after all the state and federal incentives.

When the authors studied the relationship between new and existing homes sales prices they found an interesting result.  The new homes showed a premium of $2.3 to $2.6/Watt while the average premium for existing homes was $6/Watt.  The authors blamed this disparity on the fact that the homebuilders install photovoltaic systems on their new homes as a standard, and possibly accept a lower premium to sell the houses faster.

The last part of the study compared energy cost savings of the homeowners to the sales price of the homes.  When the results were expressed as a ratio of the sales price to the annual electricity cost savings associated with PV the average was around 20:1.  This means that for every $1000 saved in energy, the houseswith PV systems sold for $20,000 more than a house without a PV system.  This was the average for existing and new homes.  The averages for both ranged from 7:1 to 31:1.

The authors of the study showed that, in California, having a PV system installed on your house will increase your home’s sale price.

There is a 2-page summary located here:


Here is a link to the full report:


Rural Energy for America Program Grants and Loans

solar-panel-on-farmAlthough the grants from the state of Ohio have expired, there are still grants available for small business or farm owners in rural Ohio to install solar panels and offset their electrical costs.  These are called REAP grants.  REAP stands for Rural Energy for America Program and they are available from the USDA.  The following is taken directly from their grant brochure.  They are currently accepting applications for grants and loans for 2012.  The program is in effect until the end of 2012.


  • The Rural Energy for America Program is intended to promote energy efficiency and renewable energy development for rural small for-profit businesses and agricultural producers.
  • The grant will not exceed 25% of the total eligible project costs. Priority consideration will be given for requests of less than $20,000. ($80,000 project cost)
  • The loans are intended to provide “gap” financing for energy related projects. The guaranteed loan will not exceed 75% of the total eligible project costs.
  • Combined guaranteed loan and grant packages cannot exceed 75% of the total project costs.
  • Renewable energy systems or energy efficiency improvements cannot benefit a residence.

Eligible Applicants

  1. An applicant must be a rural small business or an agricultural producer.
  2. The size requirement for a small business is defined by SBA at the following website: https://www.sba.gov/contracting/getting-started-contractor/make-sure-you-meet-sba-size-standards.
  3. An agricultural producer is defined as an individual or legal entity which receives 50% or more of their gross income from agricultural.
  4. Applicant must be a U.S. Citizen or have at least 51% U.S. citizen ownership.
  5. Applicant may not owe delinquent federal taxes or liens.
  6. Applicants must meet the demonstrated financial need requirements.

Eligible Areas

The project must be in a rural area or in an incorporated community under 50,000 population and not adjacent to an urban area. Project location eligibility can be found at:


Grant Request Limits

  • Renewable energy systems:
  • Maximum grant request is $500,000.
  • Minimum grant request is $2,500

There is a $500 fee for processing the grant application.  If the grant is awarded a fee of 1% of the project cost is due.  If you are interested in finding out more about this grant and loan, contact SunRock Solar at info.sunrocksolar.com or give us a call at (513) 766-6025.

100% Customer Satisfaction

solar-panel-on-roofWe here at SunRock Solar pride ourselves on complete customer satisfaction.  Not only do we demand that satisfaction, but we want all of our customers to be delighted with the work that we do.  We want them to pass our name on to their friends.

Look at some of the comments our satistisfied customers have made:

“We thought you did a fabulous job of keeping us updated and answering all of our questions.”

“Carl was very professional , took the time to help me understand the system.”

“I was a bit intimidated by the size and complexity of the project but SunRock Solar handled it with complete ease.  It was extremely well planned and executed.  I appreciated the integrity and professionalism of Carl, his technicians as well as his office staff-and all at competitve pricing compared to the non-local companies that I researched.”

“Carl Adams and his associates at SunRock are very knowledgeable and meticulous about their products, installation, and services.  They believe in renewable energy and in helping to preserve the good earth.  I highly respect their commitment and stellar work ethic.  SunRock did a superb job installing our solar system.”

And our favorite

“Sunny Days are like Paydays.”

Contact SunRock Solar to learn more about solar energy.  References are available upon request.

GEO Hosts Weatherization Webinar

solar-panel-on-the-roofAre you ready for the frigid temperatures of winter?  Want some tips on using less energy to keep warm.  Join us this Thursday, November 18 from 10:30 am to 12:00 pm when Green Energy Ohio (GEO) will be hosting a webinar entitled “Get a Head start on Winter with Weatherization Tips and Strategies.”

Green Energy Ohio, Ohio’s utilities, and other efficiency leaders will teach you how to save energy and money this winter.  Presenters will provide tips and resources for making your home more efficient, while the utilities will share about their various efficiency initiatives and programs.

This webinar is free and open to the public.

To find out more and register, go to https://www1.gotomeeting.com/register/331558016.

Sycamore Township Sells SRECs to SunRock Partner

solar-panel-on-roofSycamore Township has decided to sign a 3 year contract with the Washington D.C. based company Sol Systems.  Sol Systems has agreed to pay the township $303 for each renewable energy credit they produce.  All this passive income for the township will amount to about $21,816 each year.  Sycamore Township installed a photovoltaic solar array at Schuler Park on Deerfield Road behind the fire station.  Sol Systems has a partnership with SunRock Solar and many of our customers have signed contracts to sell their SRECs.

To quote one of our customers “Sunny days are like paydays.”

SunRock Makes the News

michael-eason-solar-systemMarcia and Michael Eason’s solar system was featured on the front page of the Home and Style Section of the Cincinnati Enquirer on Saturday, September 25th. SunRock Solar installed the system in July of 2009.  The Easons live in West Chester.  Their house was highlighted because it is part of the 2010 Solar Tour Organized by Green Energy Ohio.  The Solar Tour takes place this weekend, October 2nd and 3rd.  If you are interested in participating in the solar tour to see more of SunRock’s installations around southwest Ohio check out the website to organize your own personal tour.

SunRock in the News

solar-panel-on-rooftopsSunRock Solar is mentioned in a September issue of the Business Courier in an article entitled, “Rocknoll a Pioneer in Local Wind Turbine Technology.”  The article talks a lot about wind power and turbines that are going up in the area, but solar power is also mentioned as a system that is often combined with wind technology.   The following excerpt was taken from the article and features our work for the company Recto Molded products and its owner Per Flem.

A proven success is Recto Molded Products in Oakley, which had 198 solar panels installed in December 2009 by Blue Ash company SunRock Solar.  Recto Molded owner Per Flem estimates the company will have a revenue of about $17,000 per year on renewable energy credits.  That doesn’t even factor in the savings on reduced electricity consumption.

“There’s absolutely no question that there’s not a two-year payback on this project,” Flem said.

It cost $260,000 to install the panels.  The state of Ohio paid for half of the project and the federal government paid 30 percent.  With an added tax depreciation, Recto Molded’s net out-of-pocket cost to install the panels was somewhere around $50,000.

“Besides, it’s cool,” Flem said.  “It really is neat to be generating your own electricity.”

We think it is pretty cool too.

American Solar Energy Society 2010 National Conference

SunRock Solar and Solar 2010 Conference

staff-photoCarl Adams, of SunRock Solar, headed out to Phoenix recently to attend the American Solar Energy Society’s 2010 national conference.

He attended three days of advanced training prior to the conference and then spent the remainder of the time looking at the new solar hardware.  Workshops included

  • Solar Updates to the National Electric Code
  • Conergy Mounting Systems
  • Fronius Inverter Systems
  • Advanced System Design
  • Commissioning and Troubleshooting

The courses were taught by national experts in each of the respective fields and provided many new insights and information.  Carl attended many hands-on training sessions including one where he learned to assemble a Conergy Solar Giant ground mounting system.  The new design accommodates a 10 kW PV array and can be fully assembled in approximately 1 hour.

There were over 240 vendors with displays of solar thermal, photovoltaics, mounting systems, monitoring solutions and all sorts of other solar toys.  It was all they could do to get through the exhibit hall in the two days available.

Making SRECs Work for You

What are SRECs?

staff-photoThe term SREC stands for Solar Renewable Energy Credit and is a tradable credit that represents all the clean energy benefits of electricity generated from a solar electric system. Each time a solar electric system generates 1000kWh (1MWh) of electricity, an SREC is issued which can then be sold or traded separately from the power.

Ohio SRECs are currently trading for $320 – $350 per SREC, or $0.32 – $0.35/kWh so SRECs generated by your photovoltaic system are worth two to three times the retail cost of the electricity they generate.  These SRECs represent an income stream to owners of solar power systems which helps pay for the cost of the system while the electricity produced reduces the owner’s utility bill.  So you can save money on your utility bill and get paid for being a good citizen of the planet and generating clean, renewable energy!

SRECs can be sold on an as generated basis, or some buyers are offering upfront payments for 5 to 10 year contracts on all the SRECs your system can generate.

So who purchases SRECs?

SRECs are purchased by electrical utilities or energy suppliers who need to meet a Renewable Portfolio Standard (RPS). SRECs are also being purchased by third party traders known as SREC aggregators.  The value of SRECs are determined by three major factors:

  1. State RPS requirements
  2. Value of the state’s Solar Alternative Compliance Payment (SACP)
  3. Supply and demand of SRECs in your state

What’s an RPS

Renewable Portfolio Standard (RPS) is a state or federal policy that requires electricity suppliers to provide a certain percentage of their electricity from renewable energy resources. More than 30 states have RPS programs, and many of these states have solar RPS requirements that specifically mandate a minimum percentage of energy be produced from solar energy sources. Energy suppliers meet RPS requirements by creating or purchasing SRECs, or by paying a non-compliance fine to state regulatory authorities.

In May of 2008 the state of Ohio adopted Senate Bill 221, which defines Ohio’s RPS.   Here is short summary of the 88 page bill

  • Ohio utilities must provide 25% of retail electricity supply from alternative energy resources by 2025
  • 12.5% must be generated from renewable energy resources (Photovoltaics, solar thermal, wind, geothermal, biomass, landfill gas, fuel cells, hydroelectric )
  • At least 50% of renewable energy requirement must be met by in-state facilities
  • Solar carve out of 0.5% ( 0.5% of the renewable benchmark must be met using solar power)
  • Remaining 12.5% generated by advanced energy: clean coal, advanced nuclear power, CHP, fuel cells

In short the public utilities of Ohio have some legislated mandates to produce more clean energy each year until 2024 when they will be producing 25% of their power from renewable resources.

What’s an SACP

As mentioned above the utilities must show that .5% of their power is coming from solar, and if they can’t meet that they have to pay a Solar Alternative Compliance Payment (SACP). The SACP is the amount that utilities must pay per MWh (or per SREC) of solar electricity that they are unable to generate themselves or buy rights to through SREC purchases in order to meet the state Renewable Portfolio Standard (RPS) solar requirement.

Utilities that cannot meet their compliance standard are buying SRECs as long as the price is less than the SACP.  Utilities incur costs in purchasing SRECs, so the maximum price they are willing to pay may be below the SACP. For instance, if a utility calculates that the cost to purchase an SREC is $50, they may not be willing to pay more than $50 less than the SACP. At that price, they can save money by simply paying the SACP.  The SACP is fixed in any given year, but the price of SRECs varies based on the market forces of supply and demand.

Here is what Ohio utilities must pay if they don’t meet the compliance schedule

Year SACP SREC Prices
2009  $450 $400
2010  $400 $350
2012  $350 ?
2014  $300 ?
2016  $250 ?
2018  $200 ?
2020  $150 ?
2022  $100 ?
2024  $50 ?

As you can see the SREC price is slightly lower than the SACP.  Here is a nice chart put together by Bricker and Eckland summarizing SB 221 and the non compliance payments. SB 221 Summary Chart

Currently Ohio SRECs can be sold in Ohio, Pennsylvania, and the District of Columbia.  Michigan just adopted an RPS starting in 2010 so they may be added to the list.  Kentucky, West Virginia, and Indiana do not yet have RPS legislation in place.  The market is growing and changing quickly so check back for more updates.