A rule that limited growth of photovoltaic electricity use in Hawai'i has been eased, allowing more solar panels in areas that already have seen many installations.

The state Public Utilities Commission last week raised the limits on how-much "distributed generation" — a term applying mostly to photovoltaics — can be placed on any one circuit.

"There were a number of customers that were unable to do their system last year (who) will be able to do their projects now," said Brad Albert, a partner in Maui-based Rising Sun Solar, a firm that installs photovoltaic panels. "That's a great thing."

The change comes as Hawai'i moves toward increasing its use of renewable energy. By 2030 the state wants to get 40 percent of its electrical generation from sustainable sources.

Under the old limit, installations in circuit areas where 10 percent or more of the peak energy comes from renewable energy, costly studies were required on how they can be connected to electric grids and whether additional equipment may be needed.

The new ceiling is 15 percent. The requirement applies to utilities owned by Hawaiian Electric Industries on O'ahu, Maui and the Big Island and was initially agreed to by the utility company when it signed an agreement with the state pledging to work toward adopting more renewable energy.

"Under the energy agreement of the Hawaii Clean Energy Initiative, Hawaiian Electric pledged to encourage more distributed or customer-sited renewable energy as long as it does not damage the reliability of service to all customers," said Hawaiian Electric Co. spokesman Peter Rosegg. "Reaching this agreement on the revisions to the rule is part of fulfilling that promise."

Rosegg said the new rules and interconnection agreement are reasonable and make it easier to install more on-site renewable energy.

There are about 24 areas on O'ahu, the Big Island and Maui that are either approaching the 10 percent ceiling, or are already above it, according to maps posted online by the Hawaii PV Coalition.

Rising Sun's Albert said a neighborhood east of Lahaina will get more installations now that the limit has been relaxed and no studies are needed. He said interconnection studies can cost anywhere from $20,000 to as much as $150,000, adding to the cost of systems.

Moreover, there is no guarantee the studies will determine if a project can be connected to the grid. Albert said it may be that some areas reach the 15 percent level within the year and that it may be necessary to raise the ceiling again.