As a former University of Hawaii administrator for 22 years, Kenji Sumida knows the importance of education. So when he decided to install a solar system in his Windward home, he began by educating himself on solar power.

He then invited three Island solar companies to tell him what kind of system he should install. Two were among the largest solar companies in Hawaii. The third, Bonterra Solar, was smaller, but was one of the fastest-growing solar companies in the state — and continues to be so.

Sumida was concerned because his Maunawili neighborhood, located at the foot of the Koolaus, only gets a limited amount of direct sunlight. He also knew that there is a limit to how much private PV-created electricity can safely be fed into the Hawaiian Electric Co. power grid.


“All three companies told me my system could generate no more than 10 kilowatts,” he said.

Solving a solar problem

The companies calculated the number of PV panels Sumida would need to supply enough electricity to his house and a newer attached building where his daughter lives. And all three said he needed more than the 10 kilowatts threshold.

“Only Bonterra came up with a solution to the problem,” Sumida said. “A good PV supplier will urge you to cut your electricity demand before adding PV. That’s exactly what Bonterra did.”

Bonterra solar consultant Steve Hochart told Sumida that electric water heaters use much more power than any other appliance. But by installing a three-panel solar water heating system to serve both residences, Sumida would then be able to install a PV system as well, to meet the rest of his power needs, and still stay below the 10 kilowatts limit.


“Steve really gave me a lot of confidence,” Sumida said. “He didn’t act like a salesperson.”

The Bonterra Solar solution

“It was an innovative solution that the other two companies couldn’t come up with,” said Andrew Yani, Bonterra founder and principal. “Kenji’s solar and PV systems together cost less than what the other companies wanted to charge for a single PV system.”

Yani said that Sumida also was able to get the 30 percent federal and 35 percent Hawaii tax credits.

“I’m extremely happy with Bonterra’s service and workmanship,” Sumida said. “My monthly electric bill has dropped from $400 a month to just $50. If I were grading Bonterra, I’d give them an A-plus.”

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