Hawaiian Electric Co. is asking that homeowners and businesses that buy electricity from its utilities on Maui, the Big Island, Lāna'i and Moloka'i be barred from installing new photovoltaic, or solar power, systems until more is known about their effects on the electric grids.

Private photovoltaic systems can provide a home or business with all its energy needs and then send any excess power through the grid to other users.

Hawaiian Electric told the state Public Utilities Commission earlier this month that it wants to suspend adding new photovoltaic systems to the grid because the growing number of renewable-energy systems poses a threat to the reliability and stability of its transmission system.

It is asking the PUC to agree to the moratorium while a group is convened to study reliability issues.

"We have long known we are approaching levels of instability in the system," said HECO spokesman Peter Rosegg. He compared the situation to a bus where the driver has no control over some of the power but must keep a constant 60 mph with only a gas pedal. At the same time, the driver must keep an eye on fuel efficiency and the safety of passengers while trying to keep the engines from dying.

Rosegg said a consultant HECO retained brought up the issue of pausing the photovoltaic installations for the Hawaii Electric Light Co. on the Big Island and Maui Electric Co.'s operations on Maui, Moloka'i and Lāna'i while more work is done to understand what it will take to add more of such power to the island grids.

The filing said installations can continue on O'ahu, but that at some point, instability issues also will need to be addressed there.

The proposals have stunned the state's photovoltaic installation firms and also cast doubt on the state's efforts to get 40 percent of its electricity from renewable sources by 2030.

Operators of Neighbor Island solar companies say many will be driven out of business if photovoltaic installations are frozen.

"This is literally going to put solar contractors out of business," said Mark Duda, head of the Hawaii Solar Energy Association. The companies are gearing up to battle HECO's proposal at the PUC and are seeking help from legislators and others.

HECO's request comes less than two years after HECO signed an agreement with the state pledging to allow the amount of electricity from so-called distributed generation, or the kind represented in most rooftop photovoltaic systems, to reach at least 15 percent of peak electrical demand on any given circuit.

At present, the utilities are at less than half that level on Maui and the Big Island.

Solar firm operators said they believe having a study group delve into the issue may waylay the industry for years.

"The real story here is the utility is trying to lay a basis for maintaining its discretionary decision- making over what all its generation sources are," said Erik Kvam, a photovoltaic project developer and consultant through his Zero Emissions Leasing LLC.

"Basically, they're just trying to maintain the status quo. They're really not taking the steps they need to accelerate renewable energy."

HECO said it is continuing to accept the distributed generation projects onto its grid while the PUC mulls its request, and that it is negotiating the purchasing of power from two new wind farms on Maui and two biomass power plants on the Big Island, as well as more power from the Puna Geothermal Venture.

"What is being recommended is that we defer adding even more of the variable renewable — wind and solar — for the time being until we can ensure they can be added without causing reliability problems on the Maui and Big Island grids, or without causing negative impacts on existing renewable projects," Rosegg said.

In its filing at the PUC, HEI said that MECO and HELCO are on the leading edge of integrating renewable energy technologies, with close to 40 percent on their grids coming from large energy projects and distributed generation, mostly in the form of photovoltaic systems.

The photovoltaic falls into the category of being a variable power producer, meaning it does not produce power 24 hours a day, seven days a week. Such systems can fluctuate when clouds and storms appear.

Moreover, the utilities said, they can't monitor the output of the many photovoltaic systems and have no control over their production. The utilities argue there is now potential for systems to rise or fall below the 60 hertz (60 cycles per second, the standard for general 110-volt alternating-current electric power in the U.S.) or for circumstances to arise for the power to fall off the system and bring down the entire grid.

HECO also argues that power produced by the photovoltaic systems can displace electricity production from other renewable providers, such as large wind farms, with better system and cost benefits.

At present, distributed energy production accounts for 4.7 percent of peak demand on the Big Island and 2.9 percent of the peak on Maui. HELCO has projected the number of distributed generating installations will boost the level to 8.8 percent this year, while MECO also projects gains.

"Without implementing measures to further address the overall impacts for all island systems ... additional distributed resources that are coming online have a high likelihood of causing adverse reliability impacts," the HECO filing said.

HELCO said that several power failures occurred last year that would not have taken place or would have been smaller in scope if there were not the same amount of photovoltaic installations on the system.

"But the larger number of PV systems is resulting in some customer outages due to the effect of distributed PV tripping offline during system disturbances," Rosegg said.

The solar companies agree that there is a point at which system instability will occur. But they don't think the utilities are anywhere near that level now, and they add that most of the power generated by photovoltaic system owners is used by them, whether it be homes, stores or warehouses.

"At this point, we're starting to get pushback from the utilities at a fairly low level," said Rick Reed, president of Inter-Island Solar Supply.

"For the state to get where it needs to go with renewable penetration and a lot less oil, there has to be access to the grid."

The filing by HECO is of concern to state officials, who have a goal of getting 70 percent of energy from sustainable sources by the year 2030, 40 percent of this coming from renewable generation and 30 percent from energy efficiencies.

Ted Peck, head of the state's energy efforts, said the issue being raised by HECO needs to be addressed at some point, and that the National Renewable Energy Laboratory has set aside money to work with the state on quantifying acceptable levels.

"It's important to realize that this (HECO's PUC filing) is just a proposal," Peck said. He said the state is committed to working with various parties to find a solution that works for everyone while driving toward the goal of greater renewable energy.

"Making it a huge political issue at this point is counterproductive. There's a lot of collaboration around this issue that needs to come."