Solar panels and other system components degrade over time, leading to decreased energy output. The efficiency of solar panels typically diminishes by about 0.5% annually.[i] Solar developers have talked a lot about decommissioning their plants in 20-25 years, when the panels have lost as much as 15% of their efficiency. But decommissioning isn’t the only option, or even the most likely one. In many cases, the project owner can choose repowering over decommissioning by outfitting the project with new panels, inverters, racking, or even a new layout.
A successful solar plant doesn’t suddenly lose its value when its panels reach the end of their warranty period. For example, retaining an existing electric grid connection instead of requesting a new one can save millions of dollars and years of studies. On purchased land, project owners have every reason to repower rather than decommission. Even with leased land, though, repowering can be an attractive option for both the project owner and landowner.
Because newer panels require less space to produce the same amount of power, it may be possible in some cases to increase the plant’s overall output through repowering and expansion. In fact, it may be cost-effective to repower the plant well before the end of its engineering lifespan. Repowering may be a consideration when replacing first- and second-generation inverters, many of which need to be replaced after only 10-15 years.[ii] Some project owners may find it more cost-effective to replace the panels as well as the inverters.
Decommissioning
When a project is decommissioned, the panels, racking, and other components are removed entirely. Buried wires below a certain depth are usually left in place. Stripped topsoil is replaced and graded as needed. Often a land lease specifies details of how the land is to be left: whether decompaction takes place or drainage structures are replaced.
Steel racking can be recycled, as can certain other components. Recycling for panels is not widely available, and recycling won’t eliminate the need to dispose of many tons of waste. For more on recycling vs. landfilling panels, see my post Solar panels and recycling in NYS.
Repowering: end-of-life and periodic
Alternatively, the project owner may opt to upgrade a solar plant by replacing aging equipment. The rapid pace of innovation in solar technology means repowering can often substantially increase energy production. A project originally built with 300-watt panels, for example, could be repowered with 460-watt panels today. Newer panels are more efficient and more durable. They withstand adverse weather conditions better and last longer. Bifacial panels are becoming more common, as well. These panels feature typical solar cells that face upwards, toward the sun, as well as downward-facing panels that capture reflected light from the ground.
Given the pace of advancing technology, it may be cost-effective to replace panels well before the end of their 30-year lifespan, especially while tax incentives remain in place. Periodic repowering may become common in the years ahead. Of course, this means the older, less efficient solar panels must be removed and either reused, recycled, or landfilled.
Regulatory implications of repowering
Why keep a project in service through repowering? Interconnection costs are discussed below. Permitting for a new facility can be time-consuming and sometimes controversial. Solar siting often uses land that is open and sunny, has stable soil, and is located near transmission and transportation infrastructure. The demand for such land is relatively high, as it is desirable both for agriculture and other forms of development.
NYS’s Climate Act has very aggressive targets for renewable energy, and from a broad perspective, it makes little sense to decommission a solar facility at the end of its expected lifespan. Older wind facilities in NYS are already being repowered using taller, more efficient turbines.
The implications of repowering for permitting are still under consideration. So far, NYS has determined that major wind turbine upgrades require some amount of new or modified permitting. Similar rules will probably apply to solar installations. Changes to capacity may require upgrading grid interconnections as well.
At the local level, municipalities will have to decide what permitting an upgraded solar project requires. Few solar laws address repowering, and state-supplied sample laws fail to discuss it. To be cost-effective in NYS, solar projects have required payment in lieu of taxes (PILOT) agreements from towns and counties. Repowering may represent an opportunity to renegotiate an existing PILOT or to negotiate a new one.
Importantly, officials involved in permitting should not view solar projects as a temporary land use. The solar industry is very much aware of repowering as an option. Laws need to determine how permitting for repowered projects should be handled, and industrial development agencies should consider policies for determining PILOTs for them.
Repowering and agriculture
Many solar projects have been promoted as having a predefined lifespan, with the understanding that the land will be returned to its former condition at the end of that period. Farmers leasing their land for solar are often told that projects are not permanent fixtures and that farmland may be returned easily to agricultural use. The idea is attractive but unfortunately not supported by research or practice. No field research has been done to determine the effects of panel coverage over multiple decades, and no utility-scale solar facilities have been decommissioned and returned to agricultural use.
Even over a period of seven years, soil biochemistry changes under panels.[iii] Compaction occurs during construction and sometimes under other circumstances. Galvanized piles may leach zinc into the surrounding soil. If left in place, damaged panels may potentially leach lead and other metals,[iv] as may glass made with antimony. Anti-reflective coatings used to increase efficiency may contain PFAS and break down over time; these products require periodic reapplication.
Whatever changes to soil take place during the lifespan of a solar project are likely to be compounded by continued use for energy generation, if the facility is repowered instead of decommissioned. The long-term impacts of solar coverage remain unclear, and the assumption that panels can be removed and land returned to tillage is still speculative at best.
Repowering and grid interconnections
If a project owner can continue using a grid interconnection, the benefits are substantial in New York State. Between 2017 and 2021, projects smaller than 50 MW had average interconnection costs of $4.7 million, compared to $8.2 million for projects between 50 and 100 MW. [v] Costs for projects between 100 and 250 MW averaged $14.5 million, and projects with a capacity of 250 MW or more averaged $78.4 million. Even if upgrades are needed to increase the capacity of a repowered facility, project costs are likely to be less than for new plants.
Conclusions
Repowering saves time and resources for project developers by leveraging existing infrastructure, including land, permits, and electrical connections. As of 2025, it often takes more than six years to obtain a new grid interconnection from the NYISO,[vi] NYS’s grid operator. State permitting for a large facility can take several years, despite laws that have attempted to reduce the time required. The rapid pace of technological advancement in the solar industry makes repowering an increasingly affordable option.
As NYS seeks to meet its renewable energy targets, the need for renewable generation is increasing, not declining. It’s time for developers to stop promoting the narrative that projects will be decommissioned and immediately returned to agricultural or other use after 25 years.
In evaluating solar facilities for permits, local and state officials need to take repowering as seriously as decommissioning. Regulatory frameworks need to be established well in advance of the first wave of repowering efforts so both towns and developers can plan ahead. By owning the likelihood of repowering, developers can help protect themselves from future uncertainties.
In the years ahead, state and local governments will probably encourage investment in repowering projects. We can hope this process will be paired with efforts to increase recycling efforts and promote opportunities for reusing partially degraded solar panels.
©2025 Kris Martin
[i] Olivia Bolt, Solar Panel Energy Efficiency and Degradation Over Time, 4 April 2024, https://energytheory.com/solar-panel-efficiency-over-time/.
[ii] Emma Penrod, US solar farms are aging. Is it time to begin repowering? 6 October 2023, Utility Dive, https://www.utilitydive.com/news/us-solar-farms-are-aging-is-it-time-to-begin-repowering/690978/.
[iii] Maria Cristina Moscatelli, Rosita Marabottini, Luisa Massaccesi, Sara Marinari, Soil properties changes after seven years of ground mounted photovoltaic panels in Central Italy coastal area, Geoderma Regional, Volume 29, 2022, e00500, ISSN 2352-0094, https://doi.org/10.1016/j.geodrs.2022.e00500.
[iv] Hari Bhakta Sharma, Kumar Raja Vanapalli, Vikram Kumar Barnwal, Jayanta Bhattacharya, “Evaluation of heavy metal leaching under simulated disposal conditions and formulation of strategies for handling solar panel waste,” Science of The Total Environment Volume 780, 1 August 2021, 146645, https://www.sciencedirect.com/science/article/abs/pii/S0048969721017137?via%3Dihub.
[v] Julie Mulvaney Kemp, Joachim Seel, Joe Rand, Dev Millstein, Fredrich Kahrl, Will Gorman, Ryan Wiser (Lawrence Berkeley National Laboratory), Will Cotton and Kevin Porter (Exeter Associates), Interconnection Cost Analysis in the NYISO Territory, March 2023, https://eta-publications.lbl.gov/sites/default/files/nyiso_interconnection_costs_vfinal.pdf.
[vi] Chris Talley, Steven Zhang, State of interconnection queues — January 2024, 17 January 2024, https://www.interconnection.fyi/blog/state-of-interconnection-jan-2024.
