SEATTLE CITY LIGHT GUIDE TO INSTALLING A SOLAR ELECTRIC SYSTEM

Photo Credit: Seattle City Light

This guide is designed to provide Seattle City Light customers with information on grid-

connected solar electric systems. It provides a background on solar electric systems and

it outlines the steps to take to install a solar array at your home or business.

For solar questions not answered by this guide, please contact a Seattle City Light

Energy Advisor at (206) 684-3800 or by email at [email protected]

Table of Contents

Introduction ........................................................................................................................................................ 3

The History of Photovoltaic (PV) Technology ....................................................................................... 3

The Components of a Grid-Tied PV System .......................................................................................... 6

Siting Your System ........................................................................................................................................... 7

Selecting the Right Size System ................................................................................................................. 9

Permit Requirements ..................................................................................................................................... 11

Costs and Incentives ...................................................................................................................................... 12

Maintenance & Resale .................................................................................................................................. 14

Choosing an Installer ..................................................................................................................................... 15

Installation and Incentive Checklist: 9 Steps to Solar Power......................................................... 15

Solar Access ...................................................................................................................................................... 17

Batteries and back-up generators ........................................................................................................... 17

Additional Resources .................................................................................................................................... 18

Energy Advisors (206) 684-3800 Page 3 of 19

Introduction

More and more City Light

customers are installing solar

electric systems at their homes

and businesses. If you are

interested in producing your

own electricity and want to

reduce your personal

environmental impact, now

may be the time to learn more

about installing a solar electric

system.

 Solar electric systems are safe, reliable, pollution free, and use a renewable source

of energy—the sun. Most systems have no moving parts and are increasingly

easy to install.

 Interconnecting a customer generating system to the utility grid to take

advantage of City Light’s solar programs makes solar electric systems more

economically viable.

 Federal and state financial incentives are available for owning and operating a

solar electric system. Visit https://www.solarwa.org/solar_incentives for the latest

information.

The History of Photovoltaic (PV) Technology

The first solar cell was created

in 1883. It was inefficient by

today’s standards, converting

only 1–2% of sunlight into

electricity. The breakthrough

in solar cell technology came

in 1954 when researchers at

Bell Laboratories stumbled

across the photovoltaic (or

PV) properties of silicon while

experimenting with new

technologies. Three years

later, PV research began in

Photo Credit: Seattle City Light

Photo Credit: A&R Solar

Energy Advisors (206) 684-3800 Page 4 of 19

earnest to develop an independent solar energy source for space technologies. Thanks

to continuing research, modern commercial PV silicon cells have improved to 15 –22%

efficiency.

Historically, PV was extensively used in areas not served by a power grid. As PV prices

have dropped, PV systems are increasingly used in grid-tied applications.

A solar electric or PV cell uses a semiconductor material, like that used in computer

chips, to absorb sunlight and convert it into electricity. Multiple solar cells are linked

together to form a module or panel. Multiple modules/panels are connected to form a

PV array.

Seattle City Light has worked with customers to interconnect their solar electric systems

since the first installation in 2001. As of 2019, there are over 3900 solar customers

throughout City Light’s service territory:

Solar Growth in Seattle

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Solar growth in the Seattle City Light Service Area

Energy Advisors (206) 684-3800 Page 6 of 19

The Components of a Grid-Tied PV System

A PV System includes:

1) PV Array - Multiple PV panels installed together are called a PV array. Mounting

arrays to rooftops is most common, yet they can also be located elsewhere like

on a ground-mounted rack. The PV array produces Direct Current (DC) power.

2) DC Disconnect - The DC Disconnect is a safety device that, when manually

opened, stops power running from the array to the rest of the system. The DC

disconnect is used during system installation and anytime your contractor needs

to work on the system.

3) DC/AC Inverter - The PV array produces DC electricity; however, we use

Alternating Current (AC) electricity in our buildings and power grid. The Inverter

converts the DC power to AC power. Inverters can serve an entire PV array or a

single PV panel (called a “micro-inverter”).

4) AC Disconnect - The AC Disconnect is another safety device and is often

incorporated into the inverter. Seattle City Light does not require an AC

Disconnect on systems under 10kW(ac), unless located in network areas. For

details on this requirement, see the Seattle City Light “Requirements for Electric

Service Connection” (Chapter 14: Customer Generation)

5) Production Meter (optional) - The Production Meter measures the energy

output (in kilowatt-hours, kWh) from your system and is used to record the

amount of electricity generated. This component is not necessary for power

generation, but it is required to take advantage of Washington State’s Production

Incentive Program (closed to new enrollees as of 2019).

6) Building Circuit Breaker Panel and Standard Utility Meter - Also called your

building’s breaker box or electrical service panel, the circuit breaker panel is

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where the power from the PV system enters the building. If the building is using

electricity, the PV-produced electricity will be used first. If the building needs

more electricity than the PV system is producing, utility grid power is

automatically directed into the building. When the PV system produces more

electricity than is needed, the excess power flows back out to the utility grid. You

earn kWh credit for the excess power produced and can use that credit when the

system is not producing enough electricity to meet the consumption needs in the

building. This process is referred to as “net metering”.

Siting Your System

A well-designed solar electric

system has clear and

unobstructed access to the sun

for most of the day

throughout the year. Siting a

PV system correctly is critical

to achieve maximum power

production.

Orientation and Tilt

Optimal orientation for solar panels is true south. As you move away from true south, a

system will see production losses, up to as much as 15–25% for panels oriented east or

west. However, with advancements in technology, these losses are decreasing as inverter

manufacturers learn how to maximize off-of-south orientations. In Seattle, solar panels

produce the maximum power annually when mounted at a south-facing tilt of roughly

30 degrees.

Shading

Avoid shading as much as possible. Even minimal shading can significantly impact

power production. You will want to consider potential shading from trees, buildings,

power lines, telephone poles, and obstructions like chimneys and vent pipes. Your

contractor should include the impact of obstructions on your power production

estimate. Your site should also factor in your neighbors potential building plans.

Washington currently limits solar access rules to home owners’ associations. Before

installing solar, customers should research whether future building could affect the

shading of their array.

Photo Credit: Sun Wind Concepts

Energy Advisors (206) 684-3800 Page 8 of 19

Sloped Roof

A significant portion of your system cost will be in the installation of the panels, so if you

plan on replacing your roof in the next 5–7 years, consider doing that first. Overall, you

want to be sure your roof is in excellent long-term condition, because PV systems are

designed to last a minimum of 20 years and many will last even longer. If you are unsure

about the structural integrity of your roof, have it professionally inspected to verify its

condition and suitability.

Flat Roof

Most residential and small commercial PV systems are installed on sloped roofs, yet it is

possible to install on a flat roof. Contractors typically avoid penetrating a flat roof and

instead use some sort of ballasted (weighted) means of securing the panels against

wind. Building code officials will be concerned about the wind shear and roof loading of

such a system. A flat roof might be easier and safer to walk on, but that does not equate

to a simpler solar installation.

Tracking

Most residential and commercial PV installations are mounted to roofs and are fixed in

place. If your system is going to be mounted on a pole or a flat roof, you have the

choice of installing a tracking device. The simplest form of tracking is to seasonally

adjust the tilt angle of the panels. Automatic tracking devices allow the panels to follow

the sun as it moves through the sky, receiving direct light more often than a fixed

system. Electrically operated and thermally operated trackers have their own costs,

benefits, and drawbacks. Keep in mind that without a tracker, your PV system has no

moving parts. While automatic trackers can increase production by 20–40%, they do add

moving parts to the system, so consider operation and maintenance concerns. Pole-

mounted systems also have the additional cost of the pole installation.

Learn more about the solar potential at your home by using the National Renewable

Energy Laboratory’s (NREL) PV WATTS calculator: pvwatts.nrel.gov or

google.com/get/sunroof

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Selecting the Right Size System

Three core factors affect the

sizing of your system: your

electricity usage, space

availability on your property,

and your budget.

Your Electricity Usage

Do you want to try to produce

100% of your power or some

smaller percentage?

While any excess production from month to month will carry over as a kWh credit on

your utility bill (net metering), you will not want to install a system that produces more

than 100% of your power needs annually as the utility will not reimburse you for excess

power produced at the end of the year.

We encourage you to perform all energy-

efficiency upgrades before sizing your system or consider any future energy

conservation upgrades. You want to avoid oversizing the PV system.

To determine how much power you use right now, look for the kilowatt-hour (kWh)

consumption on your utility bill. Sum the kWh for the past year to get your annual

electricity usage. For help understanding your bill, check out seattle.gov/light/paymybill

1 kW of solar typically produces 1000 kWh annually. Remember, the seasonal output

varies in our region. 1 kW of solar radiation might produce only 20 kWh in December

but will be closer to 160 kWh in July. Here are some other considerations for sizing a

solar system:

• Annual usage for a typical Seattle home. See 2018 Annual Report:

seattle.gov/light/pubs/AnnualRpt/2018/2018_AnnualRpt.pdf

• The typical electric vehicle uses approximately 3000 kWh annually. The average

residential solar system size was approximately 8 kW in 2019.

• The average cost of solar is about $3,000 per kW before incentives or taxes.

The year is defined as April 1

through March 31

by state law, RCW 80.60.030.

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Space Availability

1 kW of solar typically requires about 80 square feet of roof space. PV Watts

(pvwatts.nrel.gov) from NREL can help map your roof or use Google’s Project Sunroof at:

google.com/get/sunroof.

Tree Removal

Please consider reviewing the City of Seattle’s policies on tree removal if you have

significant shading from trees on your property:

seattle.gov/dpd/codesrules/codes/treeprotection

Permits for solar energy systems do not consider adjacent trees or give property owners

special permission to remove trees that could interfere with their system. Tip 242, Tree

Protection Regulations in Seattle, summarizes tree regulations for private property, and

can be viewed at http://www.seattle.gov/DPD/Publications/CAM/cam242.pdf

All tips can be viewed on the City of Seattle DCI website at

web6.seattle.gov/DPD/CAMS/camlist.aspx

Panel Selection

PV panels vary in dimensions. Local contractors may have brands they install regularly.

Consult with an installer for the pros and cons of the various module sizes, the type of

panels they use and why they like them, the panels’ UL listing (required for electrical

inspection and utility interconnection) and the panels’ warranty. A standard industry PV

panel warranty is 20–25 years, and manufacturers expect the panel will produce 80% of

its rated capacity at the end of the warranty period.

Budget

It is a good idea to evaluate your budget and goals before choosing your system. Some

questions to consider include: What is my budget for this project? Will I finance or pay

for it out of my savings? Keep your budget in mind as you read the Cost and Incentives

section of this guide.

General Rule:

1 kilowatt (kW) of PV panels will require approximately 80 square feet of area. If PV panels are

unshaded, oriented to true south and mounted at approximately 30 degrees, they will produce

approximately 1,000 kilowatt-hours (kWh) per year in Seattle.

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Additionally, you may want to consider contacting lenders to help you finance your solar

project. Many services are available, and some can load the loan payment on your City

Light bill.

Permit Requirements

Electrical Permit

Electrical permits are required

for all solar electric systems

and must be secured by the

person doing the electrical

work. In most of cases this will

be your electrical contractor.

Owners with the required

planning and installation

skills, who want to complete

the installation themselves,

can also obtain the electrical permit. Your contractor must submit an electrical drawing

(One Line diagram) and the system will be subject to a field inspection after installation.

If your system has a larger capacity than 8 kW or the design is atypical, your contractor

may be required to go through a plan review.

Building Permit

Building permits in Seattle are required for solar arrays when any of the following apply:

1) The array weight is 1,000 pounds or more.

2) The installation is structurally complex determined by the Seattle Department of

Construction and Inspections (SDCI).

3) The solar project is part of building alterations or additions valued over $4,000.

4) The solar project requires construction of stand-alone support structures valued

over $4,000

Building permits may be required if your system will be installed on a flat roof. In such an installation,

specific calculations regarding roof loading and wind shear are required.

Photo Credit: Sunergy

Energy Advisors (206) 684-3800 Page 12 of 19

Land Use Requirements

In single family, multi-family and residential small lot zones, solar panels may be

mounted to extend up to four feet above the zone's height limit, and/or extend up to

four feet above the ridge of a pitched roof. Also, the total height from existing grade to

the top of the solar panels may not extend more than nine feet above the zone's height

limit.

In single family and residential small lot zones, a solar panel exceeding the zone height

limit must be placed so that it does not excessively shade the property to the north per

Tip 417, Sun chart: Determination of Solar Exposure, and can be viewed at

seattle.gov/DPD/Publications/CAM/cam417.pdf

Set-Back Requirements

Ground or pole-mounted PV systems cannot be in front yards. They must be at least 15

feet from back property line and three feet from side property line. More specifics on

set-back requirements can be found in Tip 420, Solar Energy Systems, and can be viewed

at http://www.seattle.gov/DPD/Publications/CAM/cam420.pdf

Costs and Incentives

Typical System Cost

Cost depends on several factors

(e.g. roof complexity). Typical

residential systems in Seattle in

2019 were approximately 8

kilowatts (kW) in size with an

average installed cost of about

$3,000 per kW, for a total

investment of $24,000.

Photo Credit: Western Washington Solar

General Rule:

As a point of reference, a 2 kW PV system will weigh approximately 500 pounds.

Resource:

For Seattle residents, permits may be obtained at the Seattle Department of Construction and

Inspections, 700 Fifth Avenue, 20th floor, (206) 684-8850, or at seattle.gov/dpd/permits.

For electrical permit questions, contact SDCI’s Electrical Technical Support at (206) 684-5383.

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If you generate more electricity than you consume, City Light will credit your electric bill

for every kWh of electricity sent back to the power grid. The type and timing of credit

depend on the program in which you participate.

Net Metering

Net metering allows solar customers to send excess electricity generated back to the

grid to be stored as kWh credits valued at the retail rate of electricity. The kWh credits

are tracked in your City Light billing account for use later in the year when buildings

typically utilize more grid energy than solar energy. Most customers build up kWh

credits in the summer and use them up in the winter. All customers with an

interconnection agreement and solar PV capacity of up to 100 kW will receive net

metering, and some customers with arrays up to 250 kW (listed below in Large Solar

Program) will receive it as well.

Large Solar Program

Through August 2021, most customers with solar PV over 100 kW and up to 2 MW will

receive the Large Solar Program’s Export Rate of $.0316/kWh for excess solar generation

provided to the grid. The cash credit will appear on your current bill as an export energy

credit. Large Solar Program customers with solar PV up to 250 kW that meet the

following criteria will receive net metering instead of the cash credit:

• Customers within City limits that permit and complete buildings under the terms

of the Living Building Pilot

• Customers outside City limits that receive Living Building Challenge certification

prior to 2026.

• Affordable housing performing under high energy efficiency standards

determined by City Light.

Federal Income Tax Credits

The federal Energy Policy Act of 2005, as amended by the Emergency Economic

Stabilization Act of 2008, includes provisions for individuals and businesses to claim up

to a 30% federal income tax credit for the cost of solar installations through December

31, 2021. After 2019, the tax credit declines annually:

• 30% for systems placed in service by 12/31/2019

Net metering: measuring the difference between the electricity supplied by an electric utility and

the excess electricity generated by a customer-generator's net metering system over the applicable

billing period.

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• 26% for systems placed in service after 12/31/2019 and before 01/01/2021

• 22% for systems placed in service after 12/31/2020 and before 01/01/2022

• There is no maximum credit for systems placed in service after 2008

• Systems must be placed in service on or after January 1, 2006, and on or before

December 31, 2021

• The home served by the system does not have to be the taxpayer’s principal

residence

For a great resource for information on Federal Tax Credits, visit: dsireusa.org

For a great resource for information on Solar Incentives in general, visit:

https://www.solarwa.org/solar_incentives

Maintenance & Resale

Regular Maintenance

Very little maintenance is

required on a PV system

with no moving parts.

Some system owners wash

their panels, but in the

Northwest, our climate

tends to take care of this

through precipitation. You

may want to brush off the

panels if they tend to

collect leaves, but other

than that, your system

should operate as designed with no intervention. You can also keep track of your

production by reading your production meter, checking the inverter display, or watching

your production reads on your billing statement.

Inverters have a shorter life span than solar panels and are rated for about ten years. The

system should be monitored occasionally to ensure the inverter(s) function properly.

Resale Value

The effect of a solar system on the appraised value of your home can be hard to predict,

but evidence suggests that it adds value to the home. A 2015 study from the Lawrence

Berkley Laboratory shows resale premiums of about $4 per watt, or about $15,000 for a

Photo Credit: Seattle City Light

Energy Advisors (206) 684-3800 Page 15 of 19

typical PV system: newscenter.lbl.gov/2015/01/13/berkeley-lab-illuminates-price-

premiums-u-s-solar-home-sales

Choosing an Installer

As with any construction project, best

practices include asking these basic

questions of a potential contractor:

 Do they have a business license?

 Are they licensed for the work you

want them to do (mechanical,

electrical, structural, etc.)?

 How long have they been in

business?

 How many solar electric systems have they installed?

 Will they provide references?

 Have they attended manufacturer, trade association, or other training on solar

electric installations?

In comparing bids, you should consider warranty service, installed system price

(equipment plus installation), system size, permit costs, and predicted energy output.

The Solar Installers of Washington hosts a membership roster with names of local

installers near you: solarinstallersofwa.org/membership.html

The North American Board of Certified Energy Practitioners (NABCEP) runs a quality

credentialing and certification program for renewable energy professionals. To be

NABCEP certified, a practitioner must meet installation experience requirements, sign a

code of ethics and pass a four-hour exam. Look for the NABCEP seal on contractors’

websites. More information about NABCEP and a list of certified installers can be found

at their web site: nabcep.org

Installation and Incentive Checklist: 6 Steps to Solar Power

1) System Selection

Contact installers, schedule site evaluations, and choose your system design. Use the

“Find Solar Installers” link at seattle.gov/light/solar or look at the membership list at

Solar Installers of Washington: solarinstallersofwa.org/membership.html

Photo Credit: Puget Sound Solar

Energy Advisors (206) 684-3800 Page 16 of 19

2) Interconnection Application

The following interconnection application documents are required to be completed and

submitted prior to installation (most solar installers will provide these for you):

 Application for Electric Service. This is available online at

http://www.seattle.gov/light/electricservice/application.asp

 Interconnection Application & Agreement

o Level 1 (for inverter-based generating systems 100 kW-AC or less).

Document is available online at https://energysolutions.seattle.gov/wp-

content/uploads/Level-1-Interconnection-Agreement.pdf

o Level 2-4 (for inverter-based generating systems larger than 100 kW-

AC). Document is available online at

https://energysolutions.seattle.gov/wp-content/uploads/Level-2-4-

Interconnection-Agreement.pdf

 “One Line” electrical diagram of the proposed generating system. An example

is available online at https://energysolutions.seattle.gov/wp-content/uploads/

One-Line-Example.pdf

 Production Meter Wiring Diagram. This is only if you choose to install an

optional production meter.

City Light Electric Service Representatives (ESRs) are available to work with you or your

installer to review your application submittals and fees. The application will be reviewed,

and the Interconnection Agreement will be kept on file at City Light.

Systems larger than 10kW (AC) or with battery backup will require engineering review.

Systems located in the Downtown, First Hill, or University District network areas will

require engineering review and protective equipment. This may add time, expense, and

complexity to the installation.

Submit Interconnection Applications to:

Seattle City Light

Attn: Intake Desk

1300 N. 97

Seattle WA, 98103

(206) 233-2777

3) Electrical Permit

The person installing the system, typically your solar contractor, must obtain an

electrical permit. Zoning, setback requirements, roof height, and exposure may impact

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your installation. Contact their Local Jurisdictional Authority (LJA) for land-use and

electrical permit information if you have questions about your property.

4) Electrical Inspection

Once installation is complete, call SDCI (or your local electrical permitting office if you

are outside of Seattle) for an electrical inspection. New construction requires both a

cover and final inspection—existing structures require only a final inspection. See page

11 for SDCI contact info.

After passing the electrical inspection, you must notify your ESR, who you can locate via

our service maps located at: seattle.gov/light/electricservice or by contacting the

appropriate service center.

5) Apply for Tax Credits

Individuals and businesses that install solar electric systems may be eligible for tax

credits. System qualifications and credit amounts for Washington State can be found at

https://programs.dsireusa.org/system/program?fromSir=0&state=WA, then search

“Solar” or “Renewable.”

6) Participate in City Light Programs

City Light compensates eligible customers on their utility bill when they provide excess

solar generation to the grid. If your installed solar system is up to 100 kW, you will get

kWh credits through the Net Metering program. If your installed system is over 100 kW

and up to 2 MW, you will get cash credits through the Large Solar program. Certain

high-performing buildings will receive net metering for solar installations up to 250 kW.

Solar Access

At this time, there are only solar access laws surrounding how home owners’

associations can treat solar. There are no current solar access rules for trees growing on

a neighbor’s property or if the neighbor decides to build to the limit of their building

height.

Batteries and back-up generators

Batteries and back-up generators add complexity to a solar performance-based

incentive. If you are considering battery backup or backup generators, please inform a

City Light Electric Service Representative (ESR) at the beginning of the project. Seattle

City Light does not currently offer incentives for batteries or back-up generators.

Energy Advisors (206) 684-3800 Page 18 of 19

Additional Resources

For solar questions not answered by this guide

please contact a Seattle City Light Energy

Advisor at (206) 684-3800 or by email at

SCLEnergyAdvisor@seattle.gov

For questions directly related to annual WA

state incentive payments, please contact a

Seattle City Light Energy Advisor at (206) 684-

3800 or by email at SCLEnergyAdvisor@seattle.gov. For billing questions, please contact

Customer Accounts at SCL_NetMeterBilling@seattle.gov (fastest response time) or (206)

684-5516.

If you want to do additional research, here are some resources you may find

useful:

 Solar Washington—the local chapter of the American Solar Energy Society,

providing events and newsletters: solarwashington.org

 U.S. Department of Energy Solar Energy Technologies Program—a consumer

resource covering solar basics, applications, and, research and development at

the national level: energy.gov/eere/solarpoweringamerica/solar-powering-

america-home

 Smart Electric Power Alliance—The Smart Electric Power Alliance (SEPA) is a

nonprofit organization that envisions a carbon-free energy system by 2050 and is

one of many entities globally required to make this vision a reality:

https://sepapower.org/

 Interstate Renewable Energy Council—The Interstate Renewable Energy Council

(IREC) is a not-for-profit focused on regulatory policy engagement and best

practice in the sustainable energy and energy efficiency space:

https://irecusa.org/

 Renewable Energy World—a trusted source for renewable energy news and

information with access to renewable energy-focused news, case studies,

technology trends, markets, companies, etc.:

https://www.renewableenergyworld.com/

Solar Works in Seattle!

We hope you decide to join the many Seattle area residents who are taking advantage

of a local renewable resource to generate their own clean, green power.

Photo Credit: Martha Rose

Energy Advisors (206) 684-3800 Page 19 of 19

Seattle City Light is a publicly owned utility dedicated to exceeding our customers'

expectations in producing and delivering low cost, reliable power in an environmentally

responsible and safe way. We are committed to delivering the best customer service

experience of any utility in the nation.