Hawaii is on the verge of using energy from the sun to replace much of fossil fuels as the source of the state’s electricity. A major obstacle is the uncertainty about the integrity of electrical grids at night or during cloudy days when the sun is relied upon for much of the electricity. The financial burden in determining if a risk exists should not be placed entirely on homeowners or businesses wanting to join those who already have gone solar.

The issue arises at a time when use of rooftop solar panels in a photovoltaic system is at an important crossroad. The amount of energy generated from residential photovoltaic systems in Hawaii has doubled nearly every year in the past five, according to the Hawaii Solar Energy Association. That should continue to grow at that pace for the state to reach the goal of getting 40 percent of electricity sources from sustainable sources.

The state Public Utilities Commission allows Hawaiian Electric Industries of Oahu, Maui and the Big Island to require a study to be conducted on the effect of the addition of any solar electricity system in circuits for neighborhoods where at least 15 percent of the total capacity already comes from alternative sources.

That includes wind, which is even more unpredictable than the sun.

Eleven of Oahu’s 465 circuits already have reached that point, along with 18 of the Big Island’s 140 circuits and three of Maui’s 90. Those neighborhoods effectively have reached their limit on use of solar since the cost of a study demanded by HECO ranges from $15,000 for a single-family home to $40,000 for a commercial power customer is beyond affordability. Not surprisingly, no homeowner or business has agreed to pay for a study in those 11 Oahu circuits since they reached the 15 percent threshold.

Todd Georgopapadakos, a partner in RevoluSun, a designer and installer of photovoltaic systems, told the Star-Advertiser’s Alan Yonan Jr. that his company "would literally be able to do at least double the number of projects but for this restriction."

Only 4,000 of the state’s 267,000 single-family homes have photovoltaic systems, and the disincentives in neighborhoods that have reached the 15 percent threshold could be significant. While some families and businesses may be quicker than otherwise in installing a photovoltaic system to beat the eventual threshold, neighborhoods that already have hit the limit are likely to become stagnant because of the cost of a study.

Such studies probably are needed. The 15 percent threshold, which also is required in California, was recommended by the Institute of Electrical and Electronics Engineers, according to HECO. The concern is valid that a cloud passing overhead could create a problem, even an emergency, in providing adequate voltage throughout a circuit and avoiding an outage.

There must be a better way, though — perhaps via tax or other rebates, or other cost-defraying incentives — to pay for such studies other than slapping the cost on the family or business unlucky enough to have missed the threshold cut. Until then, the road toward reducing dependence on oil will be bumpier than need be.