When Hawaiian Electric Co. began slowing rooftop solar installations last year, it pushed energy companies, legislators and residents to seek out other options, including a growing interest in going off the grid.

There are 4,500 people on Oahu waiting for approval for rooftop solar systems as a result of a September 2013 rule change where HECO required customers and contractors to be OK’d by the utility before installing photovoltaic panels. Some customers have waited as much as nine months for approval and are afraid they may miss out on lucrative tax credits if they don’t act fast.

"We hear from a growing number of customers looking for off-grid solutions," said Chris DeBone, managing partner at KumuKit and Hawaii Energy Connection.

Local solar companies — including KumuKit, Distributed Energy Partners and RevoluSun — are working on offering solar systems linked to batteries.

Power from the sun charges the batteries, which are used at night and on cloudy days to provide electricity to the home. In some cases, these systems could provide all the power for a home, as long as its energy use is modest, and allow the homeowner to go off the grid.

In most cases, the batteries would be used in conjunction with the grid. The grid powers the home when the batteries are depleted. This is called a "non-export" system because all the power from the solar system is used in the home and none is exported to the grid.

A non-export system would avoid the problem which led to HECO slowing down solar installations. HECO said it had to slow down installations because too much intermittent solar power on the grid causes instability.

"The time is right" for battery systems, said Mark Duda, Hawaii PV Coalition president and principal with Distributed Energy Partners. "There wasn’t a marketplace need. When they had an option, it wasn’t compelling to seek out storage."

The difficulty of getting HECO approval for solar systems is pushing customers away from the utility.

Rep. Cynthia Thielen (R, Kailua-Kaneohe Bay) said the conservative nature of the utility will become more of a problem for the company in the near future.

"They are clinging to a very outdated model and they absolutely must change their corporate plan," Thielen said. "I think ultimately they will go out of business."

Going off the grid, while popular on the Big Island, is still rare on Oahu.

RevoluSun installed less than a dozen energy storage systems that allowed customers to live off grid since 2009. In the last month, almost 50 customers have called the company looking to take their systems off-grid, said Colin Yost, principal and general counsel at RevoluSun.

"We are actually developing some completely off-grid systems right now and testing them. The technology has been changing rapidly. Yesterday, we met with another manufacturer," Yost said.

Energy storage is and will be fundamental, Duda said.

"There is too much uncertainty around interconnection and too many options for battery storage," Duda said. "No matter which direction this goes, you need storage."

The solar companies don’t advertise off-grid options due to the cost for consumers and anticipation for a better technology to be available soon.

"Most of the battery systems you see generally have to be replaced far sooner than the PV system itself and can make the whole thing less affordable," said Yost. "It’s getting close but we aren’t comfortable offering it on a large scale yet."

The initial prices for an off-the-grid system are still very expensive, but because of high electricity rates residents can save money over time if they go off-grid, Yost said.

"Hawaii has reached a grid-parity, meaning an off-grid system is just as cheap or even cheaper than getting energy from the utility and the reason for that primarily is because Hawaii’s electricity is so expensive," Yost said. "Once the technology gets better, if the prices stay high, you will see an exodus of customers who all leave the grid entirely."

The price of electricity in Hawaii is nearly three times the national average in large part because of the high cost of fuel oil used for power generation.

Hawaii residents paid an average of 38.66 cents a kilowatt-hour for electricity in June compared with the national average of 12.97 cents a kilowatt-hour, according to the latest data available from the U.S. Energy Information Administration.

Another issue for homeowners thinking of going solar is the ticking clock on federal tax credits.

A 30 percent federal tax credit available to those who install solar systems ends Dec. 31, 2016. There is also a state tax credit for PV system installations of 35 percent up to $5,000 per system, which doesn’t have an expiration date.

Customers can receive these tax credits even if they decide against connecting their rooftop solar to the grid.

But going off the grid is not for everyone. Current battery technology is not sufficient to power a house at the level most Hawaii residents are used to.

It requires certain lifestyle changes, said DeBone at KumuKit.

"It is a lifestyle commitment and change that people must be prepared for. People are very used to having the energy they want in the amount they want," DeBone said. When you are dependant on the sun and batteries, you may not always have the power you want.

Kohl Christensen, a big-wave surfer sponsored by the clothing maker Patagonia and a partner at the local energy company Bonterra Solar, has been living off the grid for eight years. Christensen bought, built and designed his off-grid Waialua home on a 3-acre property with his brother, Nick. Christensen uses a septic tank, a well, a solar water heater, solar panels, 16 six-volt batteries, a generator and propane tank for his range.

"If there was a better way to store the power I think everybody would go off grid. It would be easy for everybody if it were affordable," Christensen said. "The panels are cheap, the invertors are cheap, everything about the system is pretty straight forward and not that expensive anymore. The battery storage is kind of the biggest issue."