Repowering Breathes New Life into Aging Solar Installations

December 13th, 2019 |

Is your commercial solar installation not performing to expectations? Repowering may be the right solution to get your system back on track and even expand its capabilities. Our project development expert Mike Borger explains what is required to repower solar, which targeted improvements often make the most sense, and how our approach can streamline the process.

solar repowering operations and maintenance

Repair. Replace. Or just recycle, chuck it all and buy new.

Repowering describes the process of installing new or upgraded technologies and equipment to improve the performance while lowering costs associated with aging commercial solar or other renewable generation systems.

How have solar panels improved? Like so many technology products, commercial solar installations over five years old should be evaluated to see how each meets current and future performance and financial expectations. The catch is size of investment and variety of components involved in commercial solar generation installed in the past five, 10, 20 years. Newer equipment — from inverters to panels to monitoring and maintenance automation — has also significantly improved price/performance, as much as 75% improvement over systems installed just 10 years ago.

repowering solar chart declining cost of panels

Today, there’s an opportunity to boost overall performance of PV systems installed in 2015 and earlier. Assessing these systems may also uncover ways to extend their life beyond initial 20-25 year life expectancy. Commercial solar systems can be modernized and improved through a process commonly known as repowering, which typically involves installing new and enhanced technologies to increase energy generation that matches or even exceeds initial project performance and return on investment expectations.

Repowering Commercial Solar and Small Utility Solar Projects

Improving the performance and capacity of aging PV systems through equipment replacement sounds straightforward. However, the inner workings of solar PV systems are complex and often unique to each site. This means equipment replacement is far more involved than simply switching out a lightbulb.

To better understand what is required, we turned to REC Solar project development manager Michael Borger to weigh in on best practices, typical considerations and approaches to repowering.

solar repowering operations and maintenance

What is Repowering and What Are Its Drivers?

Commercial solar PV systems that are underperforming or expensive to maintain can benefit from new and more efficient technologies. Repowering often makes sense for aging solar systems as a means to increase energy yields, which typically offsets the cost of upgrades.

Common drivers for repowering include:

  1. Aging equipment that causes frequent system outages.
  2. Expiring equipment warranties and hard-to-find and costly parts.
  3. Increasing maintenance costs.
  4. Extending the solar lifespan.
  5. Increasing PV generation capacity.

If the system is failing systemically, a full system replacement is probably the right way to go. However, most systems are in better condition than their performance might suggest and repowering can provide a better ROI and get your financial targets back on track.

What Else Makes Repowering Viable Today?

A lot has changed since early commercial solar power systems came online decades ago. As long-term Power Purchase Agreements (PPA) also come up for renewal, repowering offers substantive value, especially as equipment costs have decreased significantly. Since 2014, when module price declines tapered off, non-residential solar still experienced a 55 percent price drop due to balance of system and soft costs:

repower solar chart residual systems balance

Which Commercial Solar Systems are Top Targets for Repowering?

Systems likely to benefit the most from repowering are more than 5 years old, using inverters with expired or defunct warranties, and that have not achieved their expected output in the last year.

Regardless of the cause and the symptom the inverter repowering should be considered to allow your system to hit its LCOE or savings target.

While modules, monitoring, racking, and inverters can all be sources of major underperformance, solar inverters replacement is often the best investment.

Inverters are not as robust as other parts of the PV system due to their moving parts, the heat generated from power conversion, and their general component complexity. According to the Solar Energy Industries Administration, the lifespan of PV panels is approximately 20-30 years, while a solar power inverter life is typically half that at 10-15 years. Improper design and maintenance may reduce that even further.

Inverter problems may manifest as low availability or uptime, high rates of component failure, low power conversion efficiency, accelerated corrosion, rapid filter clogging, and frequent fuse failure. As part of the inverter retrofit these design and maintenance issues can be addressed. Regardless of the cause and the symptom the inverter repowering should be considered to allow your system to hit its levelized cost of energy (LCOE) or savings target.

Moreover, equipment safety codes have also changed over the past decade, and installed equipment in older systems may not meet today’s standards. For example, UL 1741 standard was issued in 2010, and earlier models may not meet today’s safety guidelines for “grid support” and “smart inverter” functionality. This standard covers inverters, converters, charge controllers and interconnection system equipment for both stand-alone and grid-connected power systems.

Current PV System capabilities eclipse what was available to early solar system adopters, especially when it comes to monitoring systems. Years ago, it was common to manually and directly view each inverter display to determine how much electricity the system was generating. Legacy communications protocols still in use are proprietary and limited.

Today, real-time and historical data gathered through remote monitoring and internet of things (IoT) secure connectivity can be available to support system-wide monitoring that was previously difficult if not impossible.

What Are the Benefits of Repowering Solar?

As a snapshot, here are ways many companies, municipalities, schools and other commercial organizations are benefiting from repowering:

  1. System PerformanceWhile modern inverters are 98% or more efficient, the primary benefit to repowering is that the old inverter is simply offline too much. Trying to find technicians to service inverters from bankrupt companies, sourcing parts from 3rd party suppliers, or just performing the cumbersome annual maintenance intensive needs of early-technology inverters create additional costs, increase downtime, decrease generation and, overall, lower expected savings on cost of energy. Repowering with new inverters will solve these problems, operational and financial.
  2. More effective monitoringMonitoring platforms now include analytics, automated alarms and alerts, data visualizations, are protocol-agnostic, and can even include remote inverter controls. These advances help lower the cost of manual operations and speed response times when faults, failures or other issues occur. In the end, repowering makes it’s much easier to tap monitoring platforms that are forward-compatible to provide the data needed to predict and prevent equipment outages now and into the future.
  3. Expanded capabilities to incorporate energy storage and microgrids for resiliencyIn addition to restoring and improving the performance of your solar installation, repowering offers the opportunity to add other distributed generation infrastructure elements, such as batteries and microgrids for resilience. Many of these technologies are required to tap lowest rates, such as demand response and time of use. Others enable islanding from the grid, creating energy resilience in time of grid outages. Repowering provides the opportunity and potentially financing to realize these possibilities.
  4. Upgrade to better equipment with new warrantiesA number of inverter companies have exited the market. This can leave project owners holding the proverbial bag when it comes to maintenance, service and accessing technical support. That equipment may also be out of warranty and/or too expensive to maintain.

Five Tips to Repower Your Project

Like all of your renewable energy projects, repowering requires multiple players and steps, such as:

  1. Engage key stakeholders and get clarity on financial goalsWill the repowering budget come out of the maintenance department or involve capital investment from another side of the business? Approaching this side of the project properly from the outset will ensure that the repowering program and future system improvements will also go smoothly.
  2. Gather project data that’s rooted in the reality of your systemIt is critical to take a holistic look at your system and your energy consumption trends. We’ve seen customers blame their equipment for no longer covering the same percentage of their facility’s energy load, when in fact the energy requirements of their process increased due to changes in their facilities’ energy usage.

    You want to be sure that you get what you need out of a repowering project and it’s essential to first understand the system on the ground and your unique energy requirements before making any upgrades.

  3. Determine the issues Define and assess the system challenges and potential risks so that you can determine what issues you want to address. It’s tempting to swap underperforming equipment using a plug-and-play approach, but detailed engineering analysis will ensure you don’t run into new obstacles down the road.

    It isn’t exactly simple to replace inverters, monitoring systems or the panels in a solar PV system. PV systems are complex, and it is crucial that engineering studies are performed before equipment is targeted for replacement to ensure compatibility, avoid downtime and support ROI expectations.

    For example, will you need improved overcurrent protection for your new inverter? Will interconnection agreements with the utility need to be updated? Can the utility support capacity increases? Even for a straight string inverter swap, how will the locations of the exhaust be relative the adjacent inverters’ intake? Will the new inverters work with the old DAS? These challenges and more lead us to the next best practice…

  4. Establish a targeted repowering approachBased on detailed engineering analysis and input from project stakeholders, a fully informed approach on repowering and system maintenance is possible. Based on how you want to spend your time and maintenance program, you can prioritize solutions to get your system to operate as planned. A properly done repowering approach will utilize data from the DAS, a site visit, plan review for the technical approach alone.
  5. Work with an experienced partnerRepowering is a process that involves not only project management, but also engineering, procurement and construction (EPC), asset management, financing and much more. Look for a repowering partner with experience on both the EPC and operations and maintenance side of things. This will uniquely position you to fully understand the true cost of underperformance on ownership, and the real benefits of the repowering strategies used to address your current needs.

Repowering is a great means to help you extend the value of your existing investments while modernizing. If you have a commercial solar system approaching it’s 10th birthday, it’s definitely worth looking into what repowering can do for you.

About REC Solar

Michael Borger, PE brings more than a decade of operations and maintenance (O&M), engineering, and project development experience to REC Solar, a Duke Energy Renewables company. For more than 20 years, REC Solar has helped its commercial clients finance, build, integrate, operate and maintain renewable energy solutions. Today, we are one of the nations’ leading onsite commercial energy solution providers building solar generation, energy storage, microgrids and EV charging for nearly 800 installations across the US. To learn more, go to or find us @recsolar on Facebook, LinkedIn and Twitter.

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