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Solar Installation Guidebook - Appendices


Glossary of Terms

Alternating Current: Alternating current is an electric current whose direction reverses cyclically, as opposed to direct current (DC), whose direction remains constant. AC is the form of electricity that is delivered to your home or business. Solar photovoltaic (PV) systems produce DC power, which must be converted to AC by an inverter.
Alternating Current Module (AC Modules): A complete, environmentally protected unit consisting of solar cells, optics, inverter, and other components, exclusive of tracker, designed to generate ac power when exposed to sunlight
Amorphous Silicon: A very thin layer of silicon that is deposited on a substrate (glass, metal or plastic) in a manner to create a PV module. This is one of the technologies used in making thin-filmed PV modules.
Azimuth: Azimuth is the horizontal angular distance between the vertical plane containing a point in the sky and true south. The azimuth angle is the location of the sun in terms of North, East, West or South.
Array: An interconnected system of PV modules that function as a single electricity-producing unit. The modules are assembled as a discrete structure, with common support or mounting. In smaller systems, an array can consist of a single module..
Balance of System: the components in a PV system (other than PV modules) that include source-circuit combiner boxes, inverters, disconnects, overcurrent devices, electrical wiring, junction boxes and support structure.
Ballasted Mounting: A type of PV mounting system that is held on the roof using weights and does not require roof penetrations.
Batteries: In the context of PV systems, batteries are used for storing excess electricity generated by a PV system when the building is using less electricity than the system generates; batteries can store electricity for use when utility power is unavailable such as during a grid outage or for off-grid systems.
Building-Integrated Photovoltaics (BIPV): A term for the design and integration of photovoltaic (PV) technology into the building envelope, typically replacing conventional building materials. This integration may be in vertical facades, replacing view glass, spandrel glass, or other facade material; into semitransparent skylight systems; into roofing systems, replacing traditional roofing materials; into shading "eyebrows" over windows; or other building envelope systems.
Capacity rating: The maximum expected energy production from a PV system.
Cell Matching Losses: The loss in potential production due to the gaps in discrete solar cells.
Centralized Generation: A method of producing electricity with large, remote power plants that require high-voltage transmission lines to deliver the power.
Conservation: In the context of energy, using energy resources in such a way as to minimize energy consumption in relation to benefits gained.
Crystalline Photovoltaic: A type of photovoltaic cell made from a slice of single-crystal silicon or polycrystalline silicon.
Derate Factor: The value that represents the losses from the DC nameplate power rating to determine the AC power rating; the system derate factor is the mathematical product of derate factors of individual components in a PV system.
Direct Current: Solar PV systems produce electricity in direct current (DC), which is defined as the continuous flow of electricity through a conductor. In DC, electricity always flows in the same direction, which
Distributed Generation: A method of producing electricity with small, efficient power plants located near or at manufacturing facilities, universities, hospitals, and other large institutions.
Energy: Energy is the ability to do work or the amount of work actually performed. For our purposes here, energy is given in kilowatt-hours (kWh) of electricity produced by a PV system or consumed in a home or business. When most people pay their utility bill, they pay for the electricity they consumed in kWh.
Energy-efficiency: The use of a lower level of energy to accomplish the same task
Flat Plate Collectors: An arrangement of photovoltaic cells or material mounted on a rigid flat surface with the cells exposed freely to incoming sunlight.
Flexible Substrate: A flexible base on which thin film PV is laminated
Grid-connected/Grid-tied: A solar electric or photovoltaic (PV) system in which the PV array acts like a central generating plant, supplying power to the grid.
Ground Continuity: A test that is performed to verify that the safety ground is present in an electrical system.
Ground Cover Ratio: the ratio of the PV array area to the total ground area
Insolation: The amount of energy that shines on a building or area, equivalent to energy an usually expressed in annual kilowatt-hours per square meter.
Insulation Test/Megger: A test to see is the insulation of a conductor has been injured in any way to cause a short circuit when normal power is applied to it (performed by a megometer)
Integral Mounting: a method for mounting PV modules on a building where the modules are integrated into the roofing or exterior of the building itself.
Interconnection: The process of connecting an electricity-producing technology (like a PV system) to the electricity grid.
Inverter: Equipment that is used to change voltage level or waveform, or both, of electrical energy (such as converting direct current (DC) electricity produced by a solar system into the alternating current (AC) electricity that can be used in a home or building). Commonly, an inverter [also known as a power conditioning unit (PCU) or power conversion system (PCS)] is a device that changes dc input to an ac output. Inverters may also function as battery chargers that use alternating current from another source and convert it into direct current for charging batteries.

Irradiance: Sunlight intensity; the direct, diffuse, and reflected solar radiation that strikes a surface; usually measured in watts per square meter.
Isolation Device: Usually a disconnect switch that is used to cut off the PV system from the grid
Kilowatt (kW): A unit of electrical power equal to 1,000 Watts, which constitutes the basic unit of electrical demand. The Watt is a metric measurement of power (not energy) and is the rate (not the duration) at which electricity is used. 1,000 kW is equal to 1 megawatt (MW).
Kilowatt-hour (kwh): A unit of electrical energy, equivalent to the use of 1 kilowatt of electricity for one full hour. Utilities measure customers’ electric energy usage on the basis of kilowatt-hours, and electricity rates are most commonly expressed in cents per kilowatt-hour...
Life-cycle cost: The estimated cost of owning and operating a photovoltaic system for the period of its useful life.
Loads: Describes the amount of power (amps) consumed by an electrical circuit or device. Loads are usually expressed in amps but sometimes in watts. Also describes the amount of power carried by a utility system or the amount of power consumed by an electric customer at a specific time.
Losses: The discrepancy between energy or power produced at a source and the energy or power delivered to an end point; in PV systems losses are caused by individual components in the system including wiring, inverter/transformer efficiency, diodes and connections, soiling, etc.
Mismatch: The loss is solar production caused by having solar cells of differing sensitivities in the same array.
Megawatt (MW): Unit of electric power equal to 1,000 kW, or 1 million Watts.
Meter: A device used to measure and record the amount of electricity used or generated by a consumer.
Module: A complete, environmentally protected unit consisting of solar cells, optics, and other components, exclusive of tracker, designed to generate dc power when exposed to sunlight. A module is the smallest protected assembly of interconnected PV cells..
Monocrystalline: A type of photovoltaic (PV) cell technology produced by melting highly refined silicon. For a Monocrystalline silicon cell, a "seed" is dipped into molten silicon and allowed to solidify into a silicon "ingot," which is then sliced into wafers. The wafers are laminated between sheets of glass to produce a monocrystalline silicon cell. Compare with polycrystalline silicon cells.
Multicrystalline: A semiconductor (photovoltaic) material composed of variously oriented, small, individual crystals. Sometimes referred to as polycrystalline.
MVA: Apparent power expressed in million volt-amps
NABCEP: North American Board of Certified Energy Practitioners, the certifying body for solar photovoltaic and thermal installers.
Net Metering: Net metering is a billing mechanism that credits solar system owners for the electricity exported onto the electricity grid. Under the simplest implementation of net metering, a utility customer’s billing meter runs backward as solar electricity is generated and exported to the electricity grid and forward as electricity is consumed from the grid
Off Grid: A renewable energy system designed to meet the full electrical requirements of a site. Requires batteries to store energy for use at times of lower production (e.g., nighttime). May also be coupled with a generator to provide additional power supply. Often an economical alternative in locations without direct access to utility lines. Compare with grid-connected system.
Open Circuit Voltage: The voltage that occurs in a module when it is not supplying any current (i.e. when the module is disconnected from all loads). The open circuit voltage of a module can also be used to determine the open circuit voltage of a circuit/string or the entire PV array.
Orientation: A term used to describe the direction that the surface of a solar module faces. The two components of orientation are the tilt angle (the angle of inclination a module makes from the horizontal) and the azimuth (based on true South, not magnetic North/South).
OSHA: The Occupational Safety and Health Administration. Regulatory body that provides construction standards and are covered in Chapter 29 of the U.S. Code of Federal Regulations, Part 1926, Safety and Health Regulations for Construction. All PV installers should be familiar with OSHA construction standards.
Panel: A collection of modules mechanically fastened together, wired, and designed to provide a field-installable unit
PA Solar Sunshine Program: A program offered by the Commonwealth of Pennsylvania that provides rebates to help fund solar electric (solar photovoltaic, or PV) and solar hot water (solar thermal) projects for homeowners and small businesses in Pennsylvania. This program was authorized by section 306 of the Alternative Energy Investment Act, Act of July 9, 2008
PECO: Based in Philadelphia, PECO is an electric and natural gas utility subsidiary of Exelon Corporation. It serves 1.6 million electrical customers in southeastern Pennsylvania and is the state’s largest utility. All PV systems that are grid-connected in Philadelphia must meet PECO’s requirements for net metering and interconnection.
Pennsylvania Approved Solar Contractor: An installer that has been approved to participate in the PA Sunshine Program. A list of approved installers can be found on the DEP website. Installers need to meet certain criteria before being listed.
Philadelphia Department of License and Inspections (L&I):
Photovoltaic: The technology that uses a semiconductor to convert light directly into electricity.
PJM: PJM Interconnection is a regional transmission organization (RTO) that coordinates the movement of wholesale electricity in all or parts of Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and the District of Columbia.
Polarity: Having an indicated pole (as the distinction between positive and negative electric charges); Polarity of all source circuits should be checked during installation (improper polarity can cause severe damage to the array and system electronics and has been known to cause fires in some systems).
Polycrystalline Photovoltaics: See Multicrystalline
Power: Power is the rate at which energy is generated or consumed, that is, kilowatt-hours per hour (kWh/h) or kilowatts (kW)
PV Cell (also called a solar cell): The basic photovoltaic device that generates electricity when exposed to light.
PV Laminates: Flexible and lightweight PV modules that typically use triple-junction
REC: Renewable energy certificates (RECs), also known in Pennsylvania as alternative energy credits (AECs) represent the environmental attributes of the power produced from renewable energy projects. When a homeowner or business owner installs a renewable energy system (such as solar), they become the owner of these environmental attributes, or RECs, which have value in the marketplace, and, in most cases, will help reduce the cost of a system.
SREC: Solar Renewable Energy Credit: RECs generated from a solar energy system including photovoltaic and solar thermal.
RPS (Renewable Portfolio Standard): A policy set by federal or state governments requiring that a certain percentage of the area's electricity come from renewable sources.
Short Circuit Current: The current of a module measured when it is disconnected from the rest of the system. Measuring the short circuit current of a module is one way to test for good or bad modules. The short circuit current of a module can also be used to determine the short circuit current of the string/circuit or entire array.
Single Crystalline Photovoltaics: See Monocrystalline
Soiling: The accumulation of dirt on solar panels
Standard Test Conditions (STC): A set of controlled conditions under which PV modules are tested in a laboratory. The output rating of modules is typically based on output measured when subjected to these conditions.
Standoff Mounting: A method of mounting PV modules on a building where modules are mounted above and parallel to the roof surface.
String Sizing: Designing the basic electrical circuit of a PV array typically includes PV modules electrically wired in series; relevant for PV system design because the string size determines the maximum DC system voltage that the PV system will generate (important for electric code compliance).
Sun Chart: a chart denoting the position of the sun in the sky for a particular area with the altitude on the y-axis (typically 0 to 90 degrees) and the azimuth on the x-axis (typically -120 to +120 degrees or East to West). Graphs of the sun’s position in the sky can be made at different days of the year and by time of day.
System Commissioning: A quality oriented process for achieving, verifying and documenting that the performance of a system and assemblies meets defined objectives and criteria.
Thin Film Photovoltaics: A layer of semiconductor material, such as copper indium diselenide or gallium arsenide, a few microns or less in thickness, used to make photovoltaic cells.
Uninterruptible Power Supply: (UPS) — The designation of a power supply providing continuous uninterruptible service. The UPS will contain batteries.
Utility Grid (Grid): An integrated system of electricity distribution, usually covering a large area.
Utility-Scale: Utility-scale solar energy facilities are facilities that can generate large amounts of electricity to be put directly into the electricity transmission grid.
Watts (W): a standard unit of electrical power, named after physicist James Watt.

  • Kilowatts (kW): a standard unit of electrical power equal to 1,000 watts
  • Megawatts (MW): a standard unit of electrical power equal to 1,000 kilowatts

Weatherization: Modifying a building envelope to reduce energy consumption for heating or cooling; involves adding insulation, installing storm windows and doors, caulking cracks and putting on weather-stripping.



Frequently Asked Questions

1. What type of permits will we need to do the installation? Building permit? Electrical permit? Both?
Currently both types of permit applications are required. Electrical requires 3 sets of plans to be submitted along with the completed application.
2. Will we need to submit engineering files? Ex. CAD file?
Engineer sealed plans are not required for systems 10kwh or less. Plans must be hard copy, black and white or blueprint, no electronic or digital files can be accepted.
3. What are the costs of the permit/permits required?
Streamlined review fees (based upon labor costs only*): $25.00 per $1000.00 worth of work
$3.00 City surcharge
$4.00 State surcharge
$4.00 per page of the plan
Standard review fees (based upon labor costs only*): $100.00 due at time of application.
$125.00 additional due for rough wire option*
$540.00 additional due for accelerated review option*
$25.00 per $1000.00 worth of work
$3.00 City surcharge
$4.00 State surcharge
$4.00 per page of the plan
*The associated costs of electrical equipment, conductors, conduit and material shall not be included in the construction cost calculation.
4. How long does it take to get the permit/permits? Estimate on lead-time?
A streamlined review (systems < 10kwh) could take a few days. A streamlined review for Electrical Energy Systems typically includes a technical conversation about the installation. It is suggested that the Electrical contractor be present for the review. Currently, a streamlined review is conducted at the time of submittal. A standard review can take up to 25 business days. There is an option for accelerated review of standard submittals that can take up to 5 days at an additional cost of $540.00 for accelerated review.
5. We have relationships formed with qualified, certified installers/sub-contractors in Philadelphia. Are there any requirements in terms of who we use as solar sub-contractors and installers?
Only Electrical Contractors licensed by the City of Philadelphia can obtain electrical permits.
6. Is an electrician considered a licensed contractor?
No. He/she must have a license number with the City.
7. Are licenses required for laborers working under the supervision of the licensed electrician?
8. If I want my project to qualify for rebates does my electrical contractor need to be listed on the PA Sunshine Solar Rebate Program list of approved installers and be licensed with the City of Philadelphia?
9. Where is the list of approved PA solar contractors?
Go to for a list of NABCEP certified and/or IREC accredited solar installers registered with the State of Pennsylvania.
10. I’m planning to install a PV system on a roof using a pre-engineered mounting product made by a company that specializes in PV mounting systems. Do I need a building permit?
Yes, currently a building permit is always required. L&I is planning to combine the electrical and building permit applications into one application form if the licensed electrician will accept responsibility for meeting the criteria for building code requirements.
11. How do I know if my project will require a zoning permit?
Zoning permits are not required for rooftop PV systems, but are required for ground-mounted PV systems.
12. Is zoning approval or review required for Building Integrated PV installs?
13. Is a license required to build and secure the modules and racking system only?
No, but an Electrical Contractor would be listed as responsible
14. How long does it take to get permits from the City of Philadelphia?
Electrical permits: streamlined up 3 days (but may be same day); standard up to 25 days. Building permits: streamlined 1-3 days; standard up to 25 days
15. Is the interconnection agreement, or approval from PECO, required to obtain L&I permits or can the two processes proceed in parallel?
PECO approval is not required for the building permit application or Electrical permit application but it is suggested to get PECO involved way before the electrical permit submission.
16. Why do I need to coordinate with PECO so early in the process?
To ensure that the electric lines serving the home or building can accommodate a customer-sited generating unit.
17. Do you have to get the building permit before the electrical permit?
No. It is important to note two things: 1) For a standard review, it might be best to go for the building permit first since it can take longer and 2) The streamlined permit takes only 1 visit to the electrical permit counter. You do not have to apply for a separate building permit.
18. Is a structural engineer stamp required for all rooftop installations?
It is required for projects that do not meet the criteria listed in Exhibit C-3 of the Guidebook Appendices.
19. If I’m NABCEP certified, do I need any other credentials, licenses or registrations to install a PV system in Philadelphia?
Yes, the City of Philadelphia requires licensing/registration from the following:
1. State Home Repair Registration (by the State Attorney General’s Office ) for projects on 1-2 family dwellings and for contractors who perform at least $5,000 worth of home improvements – State Requirement
2. Business Privilege License (by L&I) for projects on 1-2 family dwellings all companies associated with any project within the city of Philadelphia – City Requirement
3. Contractor’s License (City Requirement by L&I) for all projects that are:
4. Not performed by an electrical contractor
5. Performed on all projects other than 1 and 2 family dwellings – City Requirement
6. Electrical Contractor’s License (by L&I) for all projects involving electrical work – City Requirement
7. Approved List of Solar Contractors (by the PA DEP Solar Sunshine Program) recommended for all projects, required for projects pursuing state rebates – RState Rebate Requirement
8. Contractors must meet insurance requirements as determined by L&I.
20. What type of labeling is required for a PV system?
NEC article 690
21. What if I have questions about the code or process for L&I?
Contact the City at Please contact us for L&I related matters, not PECO related matters.
22. Are there special permits or regulations for buildings deemed “historical”?
The Historic Commission must approve all applications for all properties on the Philadelphia Historic Registry.
23. Do contractors and/or installers need to be union employees?
24. Is waiving the electrical permit fee retroactive?
25. Does the cost of the streamlined permit follow the new electrical fee schedule for small scale solar?
26. Is the application process the same for private development versus public sector and non-profit?
27. Are walkways required if the panels are listed as able to be walked upon?
28. Are the Do-It-Yourself homemade 65 Watt unit on the internet within code and/or acceptable?
29. Are there height constraints, aesthetic ordinances and/or glare ordinance for PV Panels?
Height Constraints are in the Center City District at 18”
30. Do you accept electronic filings?
No but L&I is working towards this.
31. What is the percentage of the credit that the state of PA awards?
It is diminishing as the State meets the installed capacity goals. Currently, the rebate is at $1.75/W (approximately 25% of the cost) and will soon drop to $1.25/W (approximately 17% of the cost).
32. Where should I apply for permits for my solar project?
L&I is located on the Concourse of the Municipal Services Building at 1501 JFK Blvd. It is open Monday through Friday from 8 AM to 3:30 PM except for the last Wednesday of each month.


For Appendix C click here.

For Appendix D click here.

For Appendix E click here.