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9611 SE 36th Street
Mercer Island, WA 98040
Phone: 206-275-7662
Fax: 206-275-7663
Contact: Ross Freeman
Email: ross.freeman@merce. . .
Hours: 8:30 am - 5:00 pm (Mon - Fri)
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Solar Power on Mercer Island

As of early 2019, The City of Mercer Island's total generating capacity is over 1500 Kilowatts from more than 180 residential and commercial installations, including two arrays of 100kw each on the rooftops of local schools.

Solarize Mercer Island Campaign v2 - 2018 
Community Solar Proposal - 2015-2018 
Solarize Mercer Island Campaign v1 - 2014
City-Owned Solar - 2013
Buy solar power through PSE's Solar Choice program

Map of all Mercer Island solar sites, as of July 2018

Learn more about same-day, streamlined City solar permitting
Learn more about current WA solar incentives
Read about  the City's commitment to the Dept of Energy SolSmart Program (Feb 2017)
Read about the City's national SolSmart Gold Award (Jan 2018)

Solarize Mercer Island v2 - 2018 Residential Solar Installation Campaign

The official contracting deadline for Solarize campaign #2 was December 15, 2018.

Summer 2018: A dedicated group of community volunteers (Sustainable Mercer Island) interested in clean energy worked with the City and Spark Northwest to launch a second Solarize Mercer Island campaign with a pre-selected installer (Sphere Solar Energy). The previous Solarize campaign in 2014 led to almost 50 new installations; this time our goal was to match or exceed that number...
If you have been contemplating rooftop solar, NOW is the time to act:
Solar is more cost-effective than ever before.
Qualify for the 30% federal tax rebate (until December 31, 2019)
Time-limited, group purchasing discount
Generous WA state incentives (enrollment closes January 31, 2019!)
[Read a summary of current incentives]
Workshops began in June 2018 and have now ENDED (attendees were eligible for a FREE site assessment from the community-selected, certified installer). Please contact the installer directly with questions about any ongoing group discount.

Learn more about Solarize Mercer Island from our non-profit partner

Before the 2014 Solarize campaign, the Island had just 32 arrays, with a generating capacity of 170 kilowatts.
As of Jan 2018, the City had 112 known installations, with a combined capacity of over 900 Kilowatts. After this second Solarize campaign, another 45 installations with 470 Kilowatts of capacity were added to the Island. Today, total capacity is over 1500 Kilowatts from more than 180 installations!

Community Solar Proposal - 2015-2018

Based on the significant interest generated by the 2014 Solarize program (see below), the City has researched another clean energy project that would lower the Island's carbon footprint and offer a way for even more residents to support solar.  A large solar installation proposed for the roof of City Hall is getting closer to becoming a reality, and interest is building among Islanders.


City Hall Rooftop Solar Design"Community Solar" projects provide a way for residents to support solar, even if they don't have a suitable location on their own property.  Several such projects have recently been completed by Seattle City Light, and there are many other examples across the state.  By contributing the upfront funds to install the project (generally about half the cost of a personal installation), each participant becomes an owner-investor, and is paid by the state -- at a rate of $1.08/kilowatt-hour back in 2015-- for the energy produced by the array. This is double the rate paid for residential installations.

Annual production estimates are approximately 80,000 kilowatt-hours for the full-sized installation, and each investor is expected to see an annual return on investment, depending on their personal tax situation (though we cannot guarantee a specific return, or the State payment rate).

The 273-panel, 75 kilowatt array has been deemed technically feasible after experts assessed roof condition and lifespan, and explored the necessary electrical connections. By comparison, the City's demonstration solar array at the Community Center (see below) is 4.4 kilowatts in size. 


The City found enough investor participants to build the full-size project, and registration closed in late summer 2015. Note: Investors must be WA residents.

Project Updates

  • Nov 2015:  Due to State limits on the amount of solar funds available to our Utility (PSE), we are now waiting until early 2016 to assess the recalculated financials of the project.
  • Apr 2016:  Solar advocates were hoping that a bill in the State Legislature would have raised the cap on production incentives available to solar projects. That bill did not pass, and therefore the rate of return on solar projects will start to drop this summer.  We are in a holding pattern at this time, pending further revisions in the State program.
  • Dec 2017: Earlier in 2017, rates of return on community solar projects were still depressed due to the finite size of the funding pool available and the large number of applicants.  However, a revised solar incentives bill finally passed the State Legislature's extended session in early July 2017. This new legislation lowers Community Solar incentives from the previous maximum of $1.08/kwh to 21c/kwh in 2018 and 18c/kwh in 2019. The City is currently exploring if these far lower rates pencil out for prospective investors.
  • Jan 2019: The state solar incentive program has closed enrollment for Community Solar projects; until, the program is re-authorized by the Legislature with additional funds, the economics do not pencil out for a City project. Islanders wishing to support offsite solar power do have an option available via PSE, called Solar Choice.

Solarize Mercer Island v1 - 2014 Residential Solar Installation Campaign

The official contracting deadline for Solarize campaign #1 was October 31, 2014. The City appreciates receiving grant funding that made this program possible from the WA Dept of Commerce (Northwest Solar Communities), the King Conservation District, and Puget Sound Energy (PSE). 

Summer 2014: The City partnered with regional non-profit group Spark Northwest (known at the time as Northwest SEED) to launch a mass solar installation initiative on Mercer Island, along with help from committed citizen volunteers.

A group discount of approx 10% off normal pricing, and Washington's solar incentives at the time meant a typical system was projected to pay for itself in just five years, depending on equipment selected -- and should then last another 20-30 years. Most residents found they could cover 50-70% of their annual power needs. Low-interest solar loans were also available from local banks and credit unions.

After attend one of 5 public informational workshops, offered in-person or online June through October 2014. (photos), participants were eligible for a free site assessment to determine the feasibility of their rooftop location, and hundreds of people took advantage of this offer.  The most interested parties then signed a contract directly with the qualified solar installer (Northwest Wind & Solar) pre-selected by a Solarize volunteer committee through a competitive RFP process.

Campaign Goal & Successes:
The initial goal of the campaign was 30 signed contracts, with a "stretch goal" of 40 or more. By the end of 2014, we reached 47 contracts (46 residential and 1 small-business), with a combined capacity of 320 kilowatts (kW). That's over 70 times the capacity of the array at the Community Center.  Solarize installations averaged 7kW in size, but some were right at the 10kW maximum.

Before the 2014 Solarize campaign, the Island had just 32 arrays, with a generating capacity of 170 kilowatts.
As of Jan 2018, the City has 112 known installations, with a combined capacity of over 900 Kilowatts.


City-Owned Solar Installation - 2013

Community Center solar array and supporters
In July 2013, crews activated the first City-owned solar power project on the Island. Built entirely with grant money from Puget Sound Energy (PSE) and citizen donations, the 22-panel demonstration installation located at the Mercer Island Community and Event Center will produce approximately 4468 kilowatt hours of electricity per year, using solar panels and electrical inverters made in Washington State.

At a July 23, 2013, event, Mayor Bruce Bassett led partners, City staff, and key community stakeholders in a formal ribbon-cutting ceremony and open-house celebration. Mercer Island's success in meeting Puget Sound Energy's Green Power Challenge (to encourage adoption of renewable energy by Washington communities), led to a $30,000 challenge grant for the solar photo-voltaic (PV) project. In 2012, a citizen-based Green Ribbon Commission persuaded an additional 250 homes and businesses on Mercer Island to sign up, increasing enrollment by 55%. Area residents supportive of solar power donated an additional $5,500 towards the project.

How It Works

The installation is connected directly to the Mercer Room in the Community Center, helping power that facility and replacing power that the City would otherwise buy. The array also generates approximately $2,500 per year in revenue under the Washington State Production Incentive Program. This income will be invested in additional City energy-efficiency measures.

* Click for E-Gauge Website *
Interested community members can check on the power production of the solar array at any time by visiting our E-gauge webpage [if your browser is up to date, it will also load at the bottom of this page]. Peak production usually occurs near noon each day, and will be highest in the summer months, although modern panels do produce energy even during cloudy and rainy weather. A green line depicts power output, while a red line tracks power consumed by the Mercer Room; when the green number is greater than the red number, most of the room is running on solar power, and any excess power is distributed to the rest of the building. The E-gauge website also details the cost savings over time.

In July 2013, this City-owned demonstration array was the 25th solar project on the Island, and it brought the local production of renewable energy from solar PV to 124 kW installed. You can add your home or business to that list and start earning production income too! Learn more about renewable energy options.

Size: 4400 Watts (4.4kW)
Annual production estimate: 4468 kilowatt-hours
Number of panels: 22 x 200-Watt Silicon Energy modules
Inverter: Silicon Energy 5300
Racking: Schletter Custom Racking System
Monitoring: E-Gauge
Installer: Artisan Electric, Inc.

More installation and event photos can be found at:


The Bigger Picture

Solar power is just one component of a much broader City effort to address greenhouse gas impacts of both government operations and local residents. Examples of other programs include: improving vehicle fleet efficiency, implementing energy-saving measures in City buildings, promoting green building standards, supporting the expansion of electric vehicles, and sustainability outreach programs. Collectively, these actions will help steer the City towards meeting a 2007 resolution by the City Council to reduce greenhouse gas emissions by 80% below 2005 levels by the year 2050.


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