Solar photovoltaic systems can displace a portion of the utility power used to meet home electricity needs. They may be operated independently (off grid) or be interconnected to the grid. Off-grid systems require storage for a back-up battery. A grid-connected, customer-owned generation system is operated parallel to the SCL electricity distribution system to offset all or some of a customer’s electricity needs.
Net metering refers to an interconnected customer generation system with a meter that reads the net difference between the customer’s electricity generation and consumption. Any excess electricity generated by the customer during a billing period is credited to the customer.
All solar photovoltaic (PV) systems require an electrical permit and, in some cases, a building permit.
Review the following documents for assistance with your permit application:
- Checklist for Residential Photovoltaic systems - roof mounted
- Standard Electrical Diagram Template
- Electrical Plan Review Submittal Guide
- Photovoltaic Solar Panels Tip Sheet
Electrical Permit Requirements
Electrical permits are required for all solar photovoltaic systems. Applications that meet the following basic requirements do not require electrical plan review.
- PV modules, utility-interactive inverters and combiner boxes are identified for use in PV systems.
- Maximum load added to the panelboard is based on the rating of the panelboard’s bus/main OCPD combination and is limited to one of the following combinations:
- 225 amp bus/200 amp main OCPD-13,440 watts, maximum 70 amp inverter OCPD.
- 225 amp bus/225 amp main OCPD- 8,640 watts, maximum 45 amp inverter OCPD.
- 200 amp bus/200 amp main OCPD- 7,860 watts, maximum 40 amp inverter OCPD.
- 150 amp bus/150 amp main OCPD- 5,760 watts, maximum 30 amp inverter OCPD.
- 125 amp bus/125 amp main OCPD- 4,800 watts, maximum 25 amp inverter OCPD.
- 100 amp bus/100 amp main OCPD- 3,840 watts, maximum 20 amp inverter OCPD.
- The A/C interconnection point is on the load side of service disconnect. See NEC 690.64(B).
- For Split-Buss panels the A/C interconnection is one of the six service disconnects.
- The system meets all current NEC, City of Bellevue, and Washington Cities Electrical Code requirements.
- One-line diagram template provided by the City of Bellevue is used.
Contractors will make their first application for a residential PV permit by contacting an electrical plan reviewer to go over the plans. The electrical plan reviewer will verify that the Checklist and PV Design meet all the requirements for the permit process. If the first submittal and subsequent field inspections meet the National Electrical Code and Bellevue Electrical Code, the requirement for plan review on future PV installations will be waived and the contractor can apply for all future residential small-scale PV permits using the plan review waiver process.
Electrical systems that do not meet these requirements will require plan review.
Building Permit Requirements
Building permits will not be required for solar photovoltaic systems when all the following are met and confirmed by the installer:
- The photovoltaic (PV) system is designed and proposed for a single-family house.
- The photovoltaic system is designed for the rooftop of a single-family house that is in general compliance with applicable codes.
- The mounting system is engineered and designed for photovoltaics.
- The rooftop is made from lightweight material such as shingle.
- Panels are mounted no higher than 18 inches above the surface of the roofing to which they will be affixed. (Except for flat roofs, no portion of the system may exceed the highest point of the roof PD).
- The total dead load of panels, supports, mountings, raceways and all other appurtenances weigh no more than 3½ pounds per square foot (PSF).
- Frameless panels on at least 3/12 pitch roof weigh no more than 4½ PSF.
- Frameless panels on at least 5/12 pitch roof weigh no more than 5 PSF.
- Supports for solar panels are installed to spread the dead load across as many roof framing members as needed to ensure that at no point are loads greater than 50 pounds.
- Attachment to the roof is specified by the mounting system manufacturer.
- The method and type of weatherproofing roof penetrations are provided.
- The structure is code compliant to zone setbacks and height.
Building permits will be required for solar photovoltaic systems if:
- The residential rooftop system does not meet all of the above requirements.
- The system is for a commercial or industrial application.
- The system is not on a rooftop and requires a standalone support structure.
Design and Installation Considerations
Solar Access and Performance
For optimal solar performance, collectors should be in a location that has clear unobstructed access to the sun (free of shading from roofs, trees and other landscape features) for most of the day and throughout the year. During a site evaluation, a solar contractor should evaluate potential collector locations using a tool, such as a Solar Pathfinder, that illustrates annual shade impacts.
For rooftop installations, provide a stable and durable connection to the roof structure for the size and weight of the components used. Take extra care to ensure a leak-proof installation. For unusual, complicated or heavy installations, consult an experienced building contractor or structural engineer. If you are unsure about the structural integrity of your roof, or if it needs repair, have it professionally inspected to verify its condition and suitability. It may be necessary to make roofing improvements prior to mounting solar modules.
A safe electrical connection of solar equipment to an existing electrical service requires careful consideration and planning. Modifications to branch circuit wiring or the panel board may be necessary. A photovoltaic breaker must be connected to the breaker furthest from the main breaker. Information about all changes to the electrical system must be included in the electrical permit application. Be sure to follow all manufacturer installation instructions.
All components of the system, such as photovoltaic modules and inverters, must be listed by a nationally recognized testing laboratory. Article 690 of the National Electrical Code has requirements specific to Solar Photovoltaic Systems.
Interconnection and Net Metering Benefits
The advantage of interconnection (compared to systems operated independently of a utility grid) is that customers on the grid are assured of electricity needs being met continuously regardless of solar availability and the size of the system installed. Any excess electricity generated by the customer during a billing period is credited back to the customer. In addition, interconnected systems do not require batteries, thus avoiding inefficiencies and maintenance costs associated with battery storage.
Northwest Solar CenterA program of the WSU Cooperative Extension Energy Program, the center provides solar energy resources and educational opportunities.
The local chapter of the American Solar Energy Society, which promotes the development of solar and renewable energy through education and training. Events, articles, newsletter and links are posted on the web.
US Department of Energy – Energy Efficiency and Renewable Energy
This division of the Department of Energy has a focus on enhancing renewable and sustainable energy production. Their website links to information on types of energy, state information, funding and a consumer guide.
A joint program of the U.S. Department of Energy and the U.S. Environmental Protection Agency, providing consumer information on energy efficient products and practices.
Northwest Solar Communities
A coalition of jurisdictions, utilities, industry partners and citizen groups working together to make rooftop solar electricity more cost-effective for all. The coalition grew out of the Evergreen State Solar Partnership (ESSP), led by the Washington Department of Commerce and Northwest SEED.