Chicago powers all city-owned facilities with 100% clean energy in major climate milestone

Chicago’s clean-energy breakthrough is not sitting on a rooftop where everyone can see it. It is hiding in plain sight.

It is in the library light that flickers on before a morning rush. It is in the fire station door lifting before dawn, the water plant humming through the night, and the airport terminal glowing while travelers hurry toward their gates.

As of January 1, 2025, more than 400 city-owned buildings and facilities began using 100% renewable electricity, according to Grist and WBEZ. That includes 98 fire stations, two international airports, and two large water treatment plants. Together, those city operations use about 700,000 megawatt-hours of electricity each year.

That is a major climate milestone. But the phrase “100% clean energy” carries fine print, and Chicago’s story is where the real energy math begins.

What Chicago Actually Changed

Chicago has moved its municipal electricity load to renewable power. In plain English, the city is now covering the electricity used by city-owned buildings, streetlights, airports, libraries, fire stations, police facilities, and other operations through a clean-power deal.

The city estimates the switch will cut roughly 290,000 metric tons of carbon dioxide per year, equal to taking about 62,000 gasoline-powered cars off the road. For the nation’s third-largest city, that is not symbolic pocket change. It is a serious cut in the pollution tied to city operations.

But the boundary matters. This does not mean every apartment, restaurant, office tower, factory, car, or airplane in Chicago is powered by renewable energy. It does not erase aviation emissions at O’Hare or Midway. It covers city-controlled electricity use. That distinction is not a weakness. It is the truth, and it helps readers understand why the milestone matters without turning it into magic.

The Solar Farm Behind the Claim

The engine behind Chicago’s move is Double Black Diamond Solar, a massive project in central Illinois. The solar farm covers about 3,800 acres and has 593 megawatts of AC capacity.

McCarthy Building Companies, which completed the project for Swift Current Energy, described it in 2025 as the largest solar facility operating east of the Mississippi River. It can produce enough electricity for the equivalent of about 100,000 homes each year.

Chicago did not build the solar farm alone. It became a major buyer. Under its deal with Constellation and Swift Current Energy, the city purchases about half of the project’s output. That covers about 70% of Chicago’s municipal electricity needs.

That is where the story gets more interesting. Chicago is not just buying generic green energy from somewhere. Its demand helped support a new renewable project on the Illinois grid. Matthew Popkin, cities and communities U.S. program manager at RMI, told Grist, “Part of Chicago’s goal was what’s called ‘additionality’: bringing new resources into the market and onto the grid here.”

That word, “additionality,” is wonky. The idea is simple. The best clean-power deals do more than shuffle paper claims. They help create new, clean electricity that may not have existed without the buyer.

The Fine Print: 70% Solar, 30% RECs

Here is the part clean-energy headlines often skip. Chicago’s 100% renewable electricity claim has two parts.

About 70% of the city’s municipal electricity needs are covered by the Double Black Diamond Solar project. The remaining 30% is covered through renewable energy credits, usually called RECs. The City Renewables project profile explains that RECs allow Chicago to legally claim renewable electricity, bridging the gap between the solar farm’s output and the city’s total municipal demand.

A REC is not a physical electron traveling from a solar panel into a library outlet. The electric grid does not work like a private garden hose. Power from many sources flows together. A REC is more like a tracking certificate that says one unit of renewable electricity was generated and added to the grid.

That makes RECs useful. It also makes them debate. Supporters see them as a recognized tool that lets cities reach clean-power goals while supporting renewable generation. Skeptics worry that REC-heavy claims can make the physical grid sound cleaner than it actually is. Chicago’s deal sits in the stronger category because most of its municipal load is tied to a new solar project. But the 30% REC piece still matters.

City Officials Know the REC Question Is Real

Chicago has not tried to hide the accounting. Jared Policicchio, the city’s deputy chief sustainability officer, told Grist that the REC piece is “a feature and not a bug” of the plan. He said the city hopes its demand for renewable power will help create more local clean-energy supply over time, then added, “Our goal over the next several years is that we reach a point where we’re not buying renewable energy credits.”

That is the most important sentence in the whole story. It acknowledges both the achievement and the gap.

The city is using RECs now, but it is not treating them as the final destination. The cleaner endgame would be a more direct renewable supply, more local generation, greater efficiency, and less reliance on certificates to make the math work. For readers, that makes Chicago’s milestone less like a finish line and more like a working model.

How Chicago Got Here

This was not a one-administration climate sprint. Grist reported that the goal dates back to 2017, when then-Mayor Rahm Emanuel set the city on a path toward carbon-free power for municipal operations. In 2022, then-Mayor Lori Lightfoot signed the agreement with Constellation and Swift Current Energy, with a renewable supply scheduled to begin in 2025.

The deal was large: Grist described it as a five-year, $422 million agreement, with Swift Current building the 593-megawatt solar farm as part of the structure. The City Renewables profile says the deal includes a 12-year, 300-megawatt solar power purchase agreement that is “sleeved” into Chicago’s retail electricity contract.

That structure may sound technical, but the practical meaning is clear. Chicago used its electric bill as leverage. Instead of simply buying power year by year, it helped anchor a long-term project that brought new solar capacity to Illinois.

Jobs, Taxes, and Local Stakes

The clean-energy accounting story also has an economic side. McCarthy said Double Black Diamond created about 500 construction jobs and produced more than 1 million hours of construction work. It also said the project is expected to make $100 million in local tax revenue over its lifetime, with more than 60% directed to public schools.

The City Renewables profile says the project involved American-based businesses, including McCarthy, First Solar, and Nextracker. It also notes that Chicago’s procurement aimed to support domestic supply chains and community programs.

Angela Tovar, Chicago’s chief sustainability officer, told Grist that the plan lets the city act on climate while using its buying power to create opportunities for Chicagoans and the state. That is the civic promise behind this kind of deal: a city can cut emissions, support a new solar project, and push workforce investment at the same time.

Why Airports and Water Plants Matter

The most overlooked part of Chicago’s milestone may be the facilities themselves. Fire stations and libraries are easy to picture. Airports and water treatment plants raise the stakes.

O’Hare and Midway are included in the city’s municipal electricity claim. So are two of the largest water treatment plants on the planet, according to Grist. Those are energy-hungry systems. They do not pause when the weather gets ugly or when demand spikes. They are part of the city’s backbone.

That is why this story is bigger than a climate slogan. Clean power for essential public systems is about emissions, but it is also about modernizing how cities run the services people depend on. A streetlight, a terminal, and a water pump may not look like climate policy. In practice, they are exactly where climate policy becomes real.

What Readers Can Take Away

Chicago’s milestone is worth celebrating, but the fine print is worth reading. The city has made a serious shift by covering 100% of its municipal electricity with renewable energy. It helped bring a major new solar project onto the grid. It tied most of its demand to a specific solar farm in Illinois. It also uses RECs for the remaining share.

That blend is not a scandal. It is how many clean-energy transitions work in the real world: part infrastructure, part contract, part accounting, part ambition. The next test is the scale. Chicago aims to move all buildings citywide to renewable electricity by 2035, a goal that would reach far beyond city hall into private homes, offices, apartments, and businesses.

For now, the lights are still just lights. The planes are still boarding. The library doors still open. The water still runs. But behind those ordinary systems, Chicago has changed the math powering them.

Disclaimer – This list is solely the author’s opinion based on research and publicly available information. It is not intended to be professional advice.

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