You wouldn’t know it from the ordinary storefront of the South-end Rite Aid, but it’s the site of the Island’s largest commercial solar panel, says property manager Mark O’Shea of Morris Piha Real Estate.

On the second floor, if you shimmy up a ladder on the southern slope of the roof are a series of window-like panels. At 9.6 kilowatts (kW), O’Shea notes it’s bigger even than the 4.4 kW device installed at the Community and Events Center last July.

“Of course, it’s cloudier some days than others, but overall it seemed to make sense for us to do it,” said O’Shea.

In 2012 Puget Sound Energy (PSE) launched the Green Power sign-up campaign to encourage the use of the technology. Mercer Island was awarded a $30,000 grant for increasing the city’s adoption of renewable energy by 55 percent.

O’Shea estimates that the installation saves an average of $83 per month, or nearly $1,000 a year. Morris Piha paid almost $28,900 out of pocket for the device, installed in 2012, but last year received an annual solar production incentive rebate check of $4,784. Rebates are highest for panels made entirely in state, of which this installation was one.

Under the rebate system, when solar panel users generate more energy than they use, they feed it back into the system and are paid 54 cents per kilowatt-hour. Other incentives include a 30 percent federal tax credit and accelerated depreciation, said O’Shea, so they can more quickly write it off. He estimates the return on the investment is around 20 percent through 2020.

“We expect between late 2017 and early 2018 we’ll recoup all the money we spent,” said O’Shea.

It’s hard to make predictions beyond 2020 because utility rates will undoubtedly rise, leading to more savings.

The city has signed an agreement with Northwest SEED, a local nonprofit, to launch an installation initiative on Mercer Island, with support from the Washington Department of Commerce and PSE. The Solarize Mercer Island campaign hopes to bring 30 new residential solar arrays online. Participants will receive 10 to 15 percent off their purchase because of the savings of buying in bulk.

On Tuesday, June 2 the city hosted a free workshop for Islanders to learn more about the campaign. Sixty-five people turned out of which 45 signed up for the next step — free site assessments. Additional events will be hosted throughout the summer. For more about the city’s initiative, click here.

CORRECTION: The print version of this story incorrectly stated the city’s solar panel was .5 kW. It is 4.4 kW. The Reporter regrets this error.