Energy benchmarking · Year built

Do older Chicago buildings get worse energy ratings?

The assumption is that old means leaky. Chicago's 2023 ratings say the oldest large buildings are not the problem; the postwar towers are.

By BUILDINGChicago editors. Published September 17, 2026. Data: City of Chicago, reporting year 2023, retrieved September 17, 2026.

How the rating works, briefly

Every Chicago building covered by the benchmarking ordinance gets a placard from zero to four stars under the Chicago Energy Rating System. Stars follow the building's 1-100 ENERGY STAR score where it has one, and energy use per square foot against national medians where it does not; one-, two- and three-star buildings can earn an extra star for improving at least 10 points over two reporting years; non-reporters get zero. The score compares a building with similar buildings nationally, adjusting for climate, so a rating says how a building performs for its type, not how old it is. Coverage rules are on the City's benchmarking page.

Four-star share by decade built

• Before 1900 n=8431.0%
• 1900s n=9335.5%
• 1910s n=16426.8%
• 1920s n=35335.4%
• 1930s n=9622.9%
• 1940s n=3828.9%
• 1950s n=12027.5%
• 1960s n=24823.0%
• 1970s n=21822.9%
• 1980s n=18330.6%
• 1990s n=16737.1%
• 2000s n=39530.4%
• 2010s n=30334.7%
• 2020s n=5942.4%

Share of rated buildings at exactly four stars, by the year_built field, 2023. Buildings before 1900 are pooled. Grey bars fall below 25%. Source: City of Chicago Energy Benchmarking dataset, our computation.

The line is not a slope. The 1920s, with 353 rated buildings (only the 2000s have more), reaches 35.4% four-star and a median ENERGY STAR score of 70. The 1930s through the 1970s all sit below the citywide share, with the 1970s lowest on mean stars (2.53). Ratings recover from the 1980s on, and the 59 buildings from the 2020s post the highest share, 42.4%.

By era, and why building type matters here

Each era has a different mix of buildings, and type moves ratings a lot (offices rate far better than schools, as our building-type breakdown shows). So we split the three biggest types by era.

Rated buildings, 2023. Small cells (under about 35 buildings) swing a lot with a handful of buildings; read them as direction, not precision.

Apartments: the prewar stock rates best

Pre-1930 multifamily buildings have a median ENERGY STAR score of 74 and a mean of 3.14 stars. Multifamily from 1960 to 1979, the postwar decades, has a median of 58.5 and a mean of 2.70. The 1960s-70s dip in the all-buildings line is mostly this group: 300 of the 466 rated buildings from those two decades are multifamily.

Offices: newer does better

Office buildings run the other way. Offices built from 1980 to 2019 hold four stars about half the time (52.4% and 52.1%), against 35.0% for pre-1930 offices.

Schools: low at every age

K-12 schools rate low in every era with enough buildings to read. The older schools do somewhat better than the newer ones, but the more useful point is that no era of school building gets near the citywide share.

What this does and does not show

These are ratings for one year, 2023, and they describe the buildings still standing and reporting, not every building built in each decade. Year built is the owner-reported field; a 1920s building may have new windows, boilers and controls, and the rating reflects the building as it runs today. The data cannot say why prewar apartments rate well. It does show that construction date on its own is a poor guide to a Chicago building's rating.