The U.S. wind power industry continues to expand at a healthy rate. The Energy Information Administration (EIA) reported that wind power accounted for a record 8 percent of total U.S. electricity generation in March 2017, up from 1 percent a decade ago.

But according to a new report from IHS Markit, the existing wind infrastructure is aging, and this may drive an uptick in operations and maintenance (O&M) expenses in the future. The November 6 report says that the average age of U.S. wind turbines is around 5 years, and O&M costs average $3 billion to $4 billion annually. IHS Markit estimates that total O&M costs will exceed $40 billion from 2015 to 2025.

“The average age of the North American wind fleet will rise from 5.5 years in 2015 to 7 years in 2020, and to 14 years in 2030,” said Maxwell Cohen, senior research analyst at IHS Markit and co-author of the report. “Along with that, equipment maintenance and operating costs are increasing significantly, leading operators to focus on performance optimization and cost management. We designed this study to help wind-asset owners compare the performance of their projects against the market as a whole, as well as to help them determine the optimal O&M strategy for their business.”

The IHS Markit report includes data from nearly 300 wind projects, representing 30,000 megawatts (MW) of capacity and nearly 20,000 turbines installed in North America (about one-third of the market). Project start dates range from 1994 to 2016, and the report includes data on turbines manufactured by over 15 OEMs. The data represents more than 115,000 turbine-years of operational history, and gives study participants the ability to track projects and turbine performance over time.

Fixed non-fuel O&M costs for wind power are significantly higher than those for natural gas or coal-fired plants. According to an April 2017 EIA report, an onshore wind generation plant entering service in 2022 would incur an annual fixed O&M cost of $13.7 per MWh, compared to $1.3 per MWh for conventional natural gas. Offshore wind O&M costs are even higher, estimated at $19.6 per MWh due to the logistics of maintaining an offshore turbine. As the existing turbines age, O&M costs have the potential to increase further, according to IHS Markit.

The IHS Markit report says that O&M costs are lowest in the first year of operation, but only slightly. During the first 10 years of a wind turbine’s operations, costs average between $42,000 and $48,000 per MW. However, costs vary from project to project, and age, location and O&M strategy factor into these costs.

For more information, read the IHS Markit report here.