Fewer Arizona Public Service Co. customers are installing rooftop solar panels in the wake of state regulators' decision last November to add a $5 monthly fee for new solar customers.

APS had 280 customers in its territory add new solar installations in January. That's fewer than half the 583 customers who had installations in January 2013.

The Arizona Republic reported that solar financing and installation companies say the new state-imposed fee is responsible for the slowdown.

The Arizona Corporation Commission argued that so-called "net-metering" customers who sell APS their excess power generated by solar don't pay their full share of costs for using the power grid.

The commission partly agreed and approved a few much smaller fee than what APS requested.