The number of rooftop photovoltaic permits issued by the city Department of Planning and Permitting in August was up 53 percent from the same period last year.

The city issued 628 solar system permits in August, up from 410 in August 2014, according to data from Marco Mangelsdorf, who tracks rooftop solar permits and is president of Hilo-based ProVision Solar.

The solar industry has had a strong year for issued PV permits after nearly two years of decline. August was the sixth month in a row that permits have been up year over year.

Mangelsdorf said the increase in permits is due to a pending decision before the Public Utilities Commission that would reduce the credit solar owners get for the excess energy their PV systems send to the grid, a system known as net energy metering.

“It’s clear that the PV industry, not just on Oahu, but across the state, has enjoyed a miniboom this year due to the very effective sales scare strategy that’s been used to hype the end of the 14-plus-year net energy metering program across the Hawaiian Electric Co. territories,” Mangelsdorf said.

Separately, Oahu residents have seen high numbers of PV approvals in 2015 from the electrical utility.

HECO has approved 9,673 solar system applications this year. Of those, 5,644 were submitted before the start of the year.

The solar industry took a hit in 2013 when HECO announced that all rooftop solar systems needed utility approval before being connected to the grid. Applications started piling up after HECO was slow to approve systems in areas that already had a large number of rooftop systems. HECO said the delay was due to concerns about safety and the stability of the grid if more solar was added in those areas.

The company agreed last year to speed up its approvals. The majority of the backlog in approvals was cleared in March.

“How many of those permits equate to actual Hawaiian Electric preapproved systems cannot be definitively determined,” Mangelsdorf said.

The city issued 4,681 permits this year, according to Mangelsdorf’s data.

The solar contractors that pulled the most permits this year include Hawaii Energy Connection, Alternate Energy Inc. and RevoluSun.