From 2008 to 2012, Hawaiian Electric Company saw solar rooftop system installations double each year. As adoption again nearly doubled in 2013, 10% of the utility's customers had solar systems feeding into its grid. Hawaiian Electric recently announced a temporary slow-down of adding more solar energy onto some of the circuits on its grid. Other U.S. utilities also are imposing deterrents to small-scale solar.

Hawaiian residents pay an average of 37¢ per kWh, triple the national average. But a 6-kWh solar installation in Hawaii can produce enough power to lower an average home's electricity charges to zero. And, until now, Hawaiian Electric allowed customers that produce more energy than they consume to sell the energy back to the utility, a practice called "net metering." But Hawaiian Electric's recent moratorium blocks new installations from net metering. The company provides power to 95% of Hawaiian residents, servicing all islands but Kauai, says Hawaiian Electric spokesman Peter Rosegg. Customers are pushing back against the forced delays on new installations.

"Prohibiting Hawaii's homeowners and businesses from installing solar energy systems on the islands ... is not in the public interest," says a statement by Hawaiian Senator Mike Gabbard (D). But Hawaiian Electric claims many of its distribution circuits can't handle much more power.

"Excess energy from high amounts of PV on a neighborhood circuit can back-feed into the circuit, causing over-voltage and other power problems," says Rosegg. He says this excess is dangerous for utility crews and customers as well as for utility and consumer equipment and that it can also cause flickers or outages.

Other U.S. utilities are pushing back on net metering payments, as well. Colorado's Xcel Energy proposes halving customer payments. The Arizona Public Service utility's plan to pass a $50 monthly fee on new solar systems was met with thousands of protestors and a petition signed by 30,000 residents. The fee was dropped to $4.90 and imposed last year.

Hawaiian Electric is keeping the temporary slowdown in place while conducting engineering studies of its grid. Customers with new solar installations are temporarily barred from the net-metering program.

Net-metering pullback isn't confined to the U.S., Spain's government recently reneged on a 25-year guarantee of high buy-back rates for solar energy, leaving many solar investors in the lurch.

With more customers using solar systems than any other US utility, Hawaiian Electric maintains it is a proponent of solar and that Hawaii's small, isolated grids make it the perfect test bed for the development and testing of adaptive technologies.

"We are examining new technologies to allow higher levels of rooftop solar on neighborhood circuits," says Rosegg.