With more than 1.3 million customers affected by electric service outages last year and the majority of those outages caused by storms, state utility regulators are advising utility companies to increase tree-trimming and infrastructure replacement projects.

In an annual report released Tuesday, the state regulators, the Pennsylvania Public Utility Commission, found that the number of major outages for electricity service providers across Pennsylvania spiked from 20 in 2016 to 50 last year.

The PUC noted that the 50 major outages last year were the highest number ever recorded in the state. The commission began gathering data on the events in 1993. It defines a major outage as a service interruption that affects 5 percent of a utility's total customers or at least 2,500 customers, whichever is less, for at least six consecutive hours.

West Penn Power — which has a service area of about 10,400 square miles and about 710,000 customers in 24 Pennsylvania counties, including Butler County — had 11 major outages in 2017, the most of any Pennsylvania electric utility, according to the PUC report.

Those outages were all the result of storms or inclement weather, according to the report. The most frequent cause cited was storms with high winds taking down trees, which subsequently take down power lines.

“(It) appears recent severe storms and associated damaging effects of trees have increased significantly,” the report concludes, in part, “which is negatively impacting the distribution system.”

Although West Penn Power had the most major outages in 2017, the PUC report found that nearly ever major outage last year was caused by severe thunderstorms. Most of the storms came during the spring and summer months, and the number of customers affected — more than 1.3 million — was nearly double the number of customers affected by major outages in 2016.

In response, the PUC urged West Penn Power and utilities across the state to step up tree trimming and infrastructure improvement projects.

“If more frequent, severe storms are considered the new norm, then a more aggressive approach to tree trimming will be necessary to reduce tree outages in the future,” the report concludes, in part.

PUC officials noted that the company performs “cycle-based tree trimming” to clear trees and limbs from its service lines. In 2017, those efforts targeted more than 4,600 miles of tree trimming and 112,000 trees that were completely removed, with a special focus on ash trees damaged or killed by the Emerald Ash Borer.

West Penn Power spokesman Todd Meyers said the company intends to spend nearly $270 million on projects to enhance reliability. Last year the company spent about $235 million on such projects, Meyers said.

The company also intends to increase its investment in tree-trimming work, Meyers said, with about $49 million dedicated for such work, up from $40 million spent in 2017.

Meyers also pointed out that 2018 has seen fewer major outages across West Penn Power's service area, with four reported so far this year.