The conventional approach to residential PV system installations  involves design, engineering, documentation, sourcing of components,  receiving and handling, warehousing and unique on-site installation. An  alternative approach is to use system packages, sometimes referred to  as kits. Here I define solar electric system packages, examine their  advantages and disadvantages, outline the situations where they make  the most sense and provide a chronology of an installation utilizing a  commercially available, off-the-shelf kit.
 
  WHAT GOES INTO A PV SYSTEM PACKAGE?
Photovoltaic system packages are preengineered, documented, complete  systems. They are ordered with a single part number and are available  in a wide range of configurations from a variety of sources that  include module manufacturers, distributors and integrators.

Preengineered. System packages are professionally designed and  engineered to standard specifications. The components are selected,  based on substantial experience and testing, to work well with each  other and to endure for the life of the system. No weak links can cause  system failure due to improper design, and broad code compliance is  incorporated. In some cases, the systems are reviewed and approved by  independent agencies such as the Florida Solar Energy Center and other  governmental agencies. Proper engineering produces systems that can  perform well in a wide range of site-specific environmental conditions.


Documented Preengineered packages come fully documented and typically include a  three-line electrical drawing, mechanical drawings, installation  drawings and instructions, a complete bill of materials (BOM) and  specification sheets and warranties for major components. The  electrical and mechanical drawings make kits ?permit ready? for most  building departments. A site-specific roof plan is typically the only  additional documentation needed to apply for and pull a permit. The  same documentation often facilitates the inspection process and  provides a comprehensive package for the homeowner.

Complete systems. System packages contain all the major components  needed for installation, including modules, inverter, racking and minor  parts like fittings and hardware for module fastening and grounding. A  typical exception is the source-circuit conductors between the array  and the inverter, which must be sized for the particular installation.  System packages are bundled in a distributor?s warehouse and shipped  via common carrier. They typically come delivered on three or more  plastic wrapped pallets.

Single part number. System packages are ordered using a single part  number as opposed to the customer?s creating a BOM. The supplier  maintains an inventory of all the items on the BOM provided for the  system to ensure off-the-shelf availability and often 1- to 2-day order  fulfillment.

A wide range of configurations. Preengineered packages, due to the  variety of system sizes and installer or customer requirements, are  available in a wide range of combinations and permutations. To be  viable, system kits must offer sufficient variation to match most real  world situations in terms of physical array size, energy production  requirements, price and component manufacturer preferences. In some  cases, packages without racking may be available, thereby increasing a  system?s flexibility as it can be used with flat roof, ground- or  pole-mounting applications.


TRADE-OFFS OF PV SYSTEM PACKAGES
Utilizing system packages has some general advantages and disadvantages  compared to the conventional customized approach. The basic trade-offs  are convenience versus material cost and simplicity versus flexibility.

ADVANTAGES

Minimal engineering required. Using a preengineered system frees  solar contractors from the details of system design; they are  guaranteed a reliable, proven and standard system. The specified  inverter and modules are carefully paired. The module string sizing is  not only correct, but it also incorporates a safety margin allowing the  system to function well in a range of conditions and locations.  However, it may be up to the installer to verify that a given site?s  average high and historical low temperatures will not impact the  system?s function due to array voltages outside of the inverter?s power  point tracking range or that exceed the inverter?s maximum voltage  limit. The bottom line is that kits eliminate most of the design time a  solar engineer would need to spend on a specific residential project.  This can allow a solar business to redirect resources to other  functions, such as sales and marketing.

Less system documentation to create. The inclusion of electrical and  mechanical drawings translates to less time spent putting together a  submittal package for the local building department. Project specific  CAD drawing is eliminated or greatly reduced and simplified.


Convenience and time savings.With the conventional approach, installers need to  develop a comprehensive BOM and source the components from one or more  distributors. This is a time consuming task that is subject to error,  particularly for new installers who lack experience. Lead times on  system components, particularly modules, can vary. As a result,  materials must be ordered accordingly, inventoried and pulled when the  job starts. This requires shop space, nimble logistical skills and  significant handling.

PV system packages are logistically simpler. Ordering with a single  part number saves time. Off-the-shelf availability minimizes lead time  and guarantees everything will arrive together. In some cases, the  system can even be drop-shipped right to the job site. Customer  satisfaction is increased due to the shortened time span from the day a  contract is signed to the day the system is commissioned. Installation  is not interrupted because a part was not ordered or loaded. In  addition, less skilled labor can be used because of the simplicity of  packaged systems, and the installation learning curve is short?usually  one or two systems?speeding each successive installation.

Starting operations in new territories.When an installation business  expands into a new state or a distant geography, system packages may  enable that operation to ramp up more quickly with minimal overhead and  less field installation support, which in turn frees up company  resources.

DISADVANTAGES

Higher material cost. PV system packages cost more than purchasing  the individual components and parts. The added value in terms of  engineering, documentation and logistics typically adds a premium of  approximately 8%?10%. As a result, high volume installers typically do  not use kits. Their economies of scale enable them to purchase in large  quantities and minimize their overhead costs effectively. They also  have the experience and expertise to design and document systems. These  installers have effectively developed their own system packages.

Less flexibility. The installer is constrained by the selection of  modules and inverters available in preengineered packages. The roof  attachments may be limited to composition shingle roofs. Depending on  the package, roof penetration flashing systems may need to be purchased  separately. Also, standardized system designs cannot be applied in some  situations, such as at sites with localized shading from dormers or a  roof surface that is significantly obstructed by plumbing or air vents.  Systems may need to be custom designed to satisfy these conditions.

WHO BENEFITS MOST FROM KITS?
Clearly, solar electric system packages are not for everyone, but several categories of installers can benefit from using them.

Novice installers. System packages are ideal for new entrants into  the solar installation business, because preengineered systems embed  the design experience that the novice solar contractor lacks. They  allow the business to focus on the areas where the company does have  experience and can excel, such as sales and installation. Here, system  kits help keep the installer out of trouble, ensure a quality system  for the customer and safeguard the reputation of the industry. They  represent the best formula for success for someone new to the business.

Small or low volume installers. Preengineered systems also make sense  for small or low volume installers, including broader focused renewable  energy or green home companies. These businesses do not specialize in  PV installation but offer it as part of a larger portfolio of services.  Small companies that operate from a home or a small storefront with  limited shop space often pick up packaged systems from the freight  carrier?s dock or have them drop-shipped to the job site. These kinds  of installers often cannot justify the overhead involved in the  engineering, purchasing, inventory and logistics of custom systems.

Installers wanting a simpler approach. Regardless of volume, PV  system packages offer installers a streamlined business model that can  emphasize sales, marketing and installation.

THE PACKAGED SYSTEM PROCESS
  Selling, sourcing and installing PV system packages is fundamentally  similar to the conventional design-from-scratch approach, except it is  simpler in many ways. There are also processes unique to the  installation of system packages. These are described below using  SunWize?s Grid-Tie Systems as an example. Other suppliers? approaches  may vary, but the process is generally similar supplier to supplier.
 
  Step one: system selection. Site evaluation for PV system packages is  no different from conventional systems. What is different is how the  system is sized and selected. The conventional procedure is for a solar  consultant or salesperson to evaluate the site in terms of roof  orientation, roof pitch, available roof area and shading. That site  information would then be turned over to a designer at the office along  with electricity usage data and the customer?s energy production  objective.
 
  PV system packages, being preengineered, enable the solar consultant to  size and select the system during the initial site visit using a  configuration table. Once the desired system output is determined, the  first and most critical configuration decision is the selection of the  module. SunWize Grid-Tie System packages have three module choices that  provide a spectrum of price points and efficiencies: Sanyo (high  efficiency and price), Sharp (midrange efficiency and price) and Kaneka  (low efficiency and price). For instance, if roof space is limited,  then the Sanyo HIT 200 will likely be the best module choice to meet  the customer?s production goal. Using this as an example, the solar  consultant then goes to the Sanyo section of the configuration table.
 
  Once the module has been selected, the solar consultant needs to choose  the inverter. The inverter choice may be driven by factors such as the  installer?s preference of manufacturer. SunWize Grid-Tie Systems offer  inverters from three leading manufacturers: Fronius, SMA America and  Xantrex. The consultant then goes to the subsection for the inverter  manufacturer of choice, say Xantrex.
 
Next, the solar consultant locates the configuration with the desired  array output in either STC or CEC watts dc within the Sanyo/Xantrex  section of the configuration table. The consultant then decides whether  the system needs to be ordered with or without racking. Perhaps the  site requires a ground-mounted instead of roof-mounted array, or the  roofing material is a standing seam metal and the S-5! clamp system  will be used to mount the modules.

On the initial sales visit, the solar consultant, already knowing the  dimensions of the specified modules, can determine how to best arrange  them on the roof. PV system arrays are modular in their design,  enabling them to be configured in a variety of ways?portrait,  landscape, one large array, two or more smaller arrays and so forth.  SunWize packages its modules into ?panels? of three, four or five  modules. The panels can be mounted separately or connected to one  another using rail splice kits.


Step two: purchasing and delivery. Once a system is selected, purchasing is  simple. An order is placed using the unique single part number for the  system. Because all system components are in stock, installers can time  the purchase close to the installation date, minimizing their carrying  costs and improving cash flow. Installers can request the electrical  drawing ahead of system delivery to complete the permit submittal  package.

Installers can have systems shipped to their shop or, because  everything is shipped together, directly to the job site. Job site  delivery is logistically more challenging because the timing is  difficult to predict. Not only does someone have to meet the delivery,  but also the delivery address often has to be accessible to a  semitruck. The installer can specify a truck equipped with a lift gate  and pallet jack for easier unloading. Another option is to pick up the  shipment at the freight carrier?s dock and take it to the job. Aside  from routine inspection for freight damage, the installer simply double  checks that all parts were delivered, using a complete BOM included  with the shipping documents.

Step three: installation and inspection.Prior to installation, the  lead installer typically makes a site visit to determine the inverter  mounting location and to size the homerun cabling before purchasing the  conductors, conduit and fittings for the runs between the array and the  inverter and the inverter and the electrical panel.

Once the crew arrives at the site, installing a system package is  virtually identical to installing a custom designed system. That is,  all the components and parts are present and installed according to  standard practices. Again, with PV system packages, the installation is  less likely to be disrupted while someone makes a run for a missing  part.

Using system kits can make it easier to build good relationships with  building officials. In some areas with volume package sales, local  inspectors have developed a level of familiarity and comfort with  preengineered systems. In many ways this is similar to the relationship  that designers and installers of custom systems build over time with  inspectors, but it happens more quickly. The detailed documentation  provided with preengineered systems and their wide deployment may speed  sound relationships between the installer and the AHJ.

The handoff of the system to the customer is enhanced by the  documentation provided with system packages. Customers receive not only  the technical drawings and installation instructions but also all the  manufacturers? manuals and warranty information in one binder?something  that is often overlooked by busy installers getting ready for the next  job.

PREDICTING THE FUTURE OF PV SYSTEM PACKAGES
PV system packages will eventually dominate the market for residential  systems, whether they are developed by distributors, manufacturers or  installers. As the market continues to grow, the disparity between the  largest and smallest installers will also increase. As larger companies  absorb midsized installers, the landscape will eventually consist of a  small top tier of increasingly larger installation companies and an  increasingly wide variety of small players.

The broad bottom tier will include more electrical, roofing and general  contractors diversifying into solar as the housing market struggles to  recover. PV system packages will serve the needs of that tier. The top  tier will effectively develop its own system packages, and these will  form the backbone of its residential business. This latter trend is  well underway as larger installers standardize their designs in the  interests of efficiency and cost savings.

Residential solar electric systems will continue their evolution from  custom designed systems to off-the-shelf electricity generating  "appliances." Preengineered systems will continue to play a key role in  this evolution.
REF:    http://solarprofessional.com/