Yes, solar panels can be built on closed landfills, and across the United States they already are. A capped landfill is usually flat, open, close to roads and power lines, and unsuitable for houses or offices. That combination makes it one of the more sensible places to put a solar array. In late 2021 the clean-energy research group RMI estimated that U.S. landfills with enough public data could host at least 63 gigawatts of solar capacity, a figure the press widely described as a 60 to 70 percent jump on the country's installed solar base at the time.
Below is what that estimate really means, how landfill solar projects are designed around the waste underneath, which projects made headlines, and what to keep in mind when you read big numbers about them.
Why old dumps make good solar sites
Once a municipal landfill stops taking waste, it is sealed with a cap: layers of compacted soil, clay or plastic liner and topsoil that keep rain out and gases in. For decades afterwards the owner must keep monitoring groundwater and landfill gas and repairing the cover. The ground keeps settling as buried material decomposes, so ordinary buildings with deep foundations are generally off the table.
Solar panels ask much less of the land. They are light, they sit close to the surface, and they need sun and a grid connection more than they need firm bedrock. The U.S. Environmental Protection Agency points out that landfills often have large areas with a gentle grade of zero to two percent, sit near transmission lines and busy roads, and are offered at lower land costs than open countryside. Using them spares farmland, forest and wildlife habitat that might otherwise be cleared for a solar farm.
There is also no shortage of candidates. The EPA notes that the country had nearly 8,000 operating municipal landfills in 1988 but only a little over 1,200 by 2024. Most of the rest have closed, and RMI counted more than 10,000 closed landfills in total.
What the 63-gigawatt estimate actually says
RMI's 2021 analysis looked at 4,312 closed landfills for which there was adequate information and calculated that they could host at least 63 GW of panels. According to RMI, full development could generate about 83 terawatt-hours of electricity a year, enough for roughly 7.8 million homes.
Two points help when you meet this figure in headlines.
- It is a potential, not a plan. No company proposed to build 63 GW. The number describes what the suitable sites could physically hold if every one were developed.
- Gigawatts measure capacity, not output. A gigawatt is the maximum a system can produce at a given moment in full sun. What households actually use is energy over time, measured in watt-hours. That is why RMI gives both the 63 GW capacity and the 83 TWh yearly generation.
The comparison with the national total also dates quickly. RMI compared its estimate with U.S. solar installed through 2020, and described it as about 70 percent of that base; some reports rounded it to 60 percent. The national fleet has grown a great deal since, so the same 63 GW would be a much smaller share of today's capacity. The useful takeaway is the order of magnitude: closed landfills are a large, mostly untapped resource.
Projects that made the news
The first wave of coverage, led by Good News Network in December 2021, highlighted three projects that show the range of what landfill solar can look like.
Urbana, Illinois: community solar for local households
The developer Nexamp built a community solar farm on about 40 acres of a capped landfill in Urbana. The site holds roughly 14,000 panels with a capacity of around 5.2 megawatts. Low- and middle-income residents nearby can subscribe and receive a discount on their electricity bills, which is the basic idea of community solar: people who cannot put panels on their own roof can still buy into a local array.
Houston, Texas: the Sunnyside project
In Houston's Sunnyside neighbourhood, IKON Environmental Energy was developing a solar farm on a 240-acre former landfill. Early reports gave quite different figures for its size. Good News Network described 70 MW serving 12,000 homes, while RMI described a 52 MW farm powering about 5,000 homes and offsetting around 120 million pounds of carbon dioxide a year. Treat the exact number as a moving target from the planning stage. Plans for the site also included electric-vehicle charging, a community garden and a bio-digester that turns organic waste into energy and fertiliser, so the project was pitched as a neighbourhood asset rather than only a power plant.
Annapolis, Maryland
A third example covered an 80-acre closed landfill in Annapolis fitted with about 55,000 panels, reported to generate power for around 2,500 people.
RMI also found that almost three quarters of operating landfill solar projects at the time were in just four states: Massachusetts, Connecticut, New Jersey and New York. Strong state incentives and scarce open land in the Northeast explain much of that pattern.
The engineering challenges
Building on a landfill is cheaper on paper, but it brings its own design rules. The cap is the most important piece of the site, and the array must never puncture it. Normal solar farms drive steel posts or pour concrete footings deep into the ground; on a landfill that would break the liner. Developers instead tend to use ballasted mounts, frames weighed down with concrete blocks that sit on the surface.
Other considerations include:
- Settlement. Waste compresses unevenly over time, so racking must tolerate shifting ground, and regular inspections are needed.
- Weight limits. The cap and slopes can only carry so much load, which affects panel layout and the access roads for maintenance trucks.
- Landfill gas. Methane and other gases still move through the waste. Wiring and equipment have to be placed so they do not create ignition risks, and gas-collection wells must stay accessible.
- Stormwater. Panels change how rain runs off the surface, and erosion can damage the cover.
- Tracking systems. Single-axis trackers that turn panels to follow the sun, common on new solar farms, were generally described as impractical on landfills in 2021, so most landfill arrays use fixed tilt.
The EPA, working with the U.S. national renewable energy laboratory, publishes a best-practices guide for siting solar on municipal landfills that covers these issues in detail. Each site has to be judged on its own records: the age of the cap, the type of waste, the slopes and the existing post-closure obligations.
Who benefits, and common misconceptions
When landfill solar works well, several groups gain at once. The landfill owner, often a city or county, earns lease income from land that previously cost money to maintain. Nearby residents can get cheaper electricity through community solar subscriptions. And the region adds clean power without clearing new land. RMI and others have also stressed the environmental-justice angle: many landfills sit next to lower-income neighbourhoods that lived with the dump for decades, and a solar farm can return something to them.
A few myths are worth correcting:
- "The panels clean up the landfill." They do not. The waste and the monitoring obligations stay exactly as they were. Solar is a reuse of the surface, not a remediation.
- "Every closed landfill could get panels tomorrow." Many sites lack data, sit far from a grid connection, have steep slopes or caps that need repair first.
- "Landfill solar is always cheaper." Land costs are lower, but special foundations, environmental permits and grid upgrades can add expense. The economics depend on local incentives and electricity prices.
How to judge a landfill solar proposal
If a project like this is proposed in your town, a handful of questions get to the heart of it quickly. Who owns the landfill and who is responsible for the cap during the solar lease? How will the panels be anchored, and has the design been reviewed by the state environmental regulator? Is there a grid connection nearby with spare capacity? Will local households be able to subscribe, and at what discount? And what happens to the panels and the site at the end of the project's life?
The bigger picture is encouraging. Old dumps are one of the clearest cases of land with few competing uses, and turning them into power plants lets communities add renewable energy while protecting fields and forests elsewhere. The estimate of 63 GW is best read as an invitation to look closely at the sites near you, not as a promise already kept.
Sources: Good News Network, December 2021; RMI: A bright future for landfill solar; EPA: RE-Powering America's Land; EPA: Best practices for siting solar on municipal landfills.
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