Which do you think has more impact, a sports stadium or a supermarket?

Updated 10 a.m.

Ever wonder how Philly’s biggest buildings are treating the environment? How much CO2 the Comcast Center produces and how much electricity the PECO Building generates have a lot to do with Philadelphia’s overall carbon footprint.

With the planet experiencing ever more catastrophic weather events and facing climate threats to everything from development to agriculture to commerce, it’s important for major U.S. cities to keep track of this footprint — and work to reduce it.

Every year since 2013, Philadelphia’s Office of Sustainability has collected data on the energy used by buildings that are at least 50,000 square feet to illuminate each property’s environmental impact.

Since 2013, there has been at least a 12% reduction in total greenhouse gas emissions from buildings participating in the program. And in the last year, Philly’s average Energy Star score among big buildings gone from 65 to 55 — showing increased efficiency. (That’s still higher than the national Energy Star average score of 50.)

The data is a useful tool. Ideally, just the act of keeping track of this information should inspire building owners to identify their carbon footprint and reduce it. But the method is not bulletproof — since the numbers are self reported, there’s a decent chance they’re riddled with unexpected errors.

Here are the rates of a few popular Philly properties. The “EUI” figure represents energy use compared to the building’s size, so it’s a better way to judge how different properties are doing compared to one another.

2 Penn Center

EUI: 64.1

Total greenhouse gas emissions: 2,986.9

PECO Building

EUI: 87.6

Total greenhouse gas emissions: 7,616.9

Comcast Center

EUI: 78.8

Total greenhouse gas emissions: 11,402.1

City Hall

EUI: 101.6

Total greenhouse gas emissions: 4,823

Temple’s Morgan Hall

EUI: 105.8

Total greenhouse gas emissions: 5,224.4

Wells Fargo Center

EUI: 114.7

Total greenhouse gas emissions: 9,582.8

Philadelphia Museum of Art

EUI: 188.5

Total greenhouse gas emissions: 12,207.4

ShopRite of Roxborough

EUI: 272.4

Total greenhouse gas emissions: 1,242.2

Curran Fromhold Correctional Facility

EUI: 272.8

Total greenhouse gas emissions: 8,839.1

Curious about another big building? You can search the Office of Sustainability’s map here.

Incomplete data, but better than nothing

Philadelphia Code mandates that large city properties submit all the necessary numbers, including electricity, water, gas, fuel and steam use.

That data may be easy for energy experts to calculate — but it’s definitely a challenging ask for regular building managers and facilities workers, several of them told Billy Penn. And if they don’t submit every required piece of info in the exact proper format, they’ll be marked “incomplete” and potentially fined hundreds of dollars each day.

A lot of people thought they had turned in their numbers correctly.

The Edge, a student housing complex at Temple, is marked incomplete, but assistant general manager Branden Bennett had no idea his submission had flaws.

Roxborough Memorial Hospital is in the same boat — with their numbers marked “not available” — but spokesperson Michelle Aliprantis is under the impression that the data was inputted correctly.

And data for the entirety of Drexel University was marked “not available” — even though the campus buildings were entered correctly. University spokesperson Britt Faulstick said the school’s facilities manager was confused about the submission process.

“He did submit the data,” Faulstick said. “He was a little bit concerned because it’s his first year doing it, and I think he was a couple hours late submitting into the portal, so maybe that caused it.”

When someone’s dataset is incomplete, the Office of Sustainability throws a red flag via email — but property owners say they don’t always catch it. It’s such a messy system that at the time of the submission deadline, senior program manager Richard Freeh said 40% of the entries were incomplete.

“In most cases it’s not a reflection of, ‘This building owner is naughty, and they didn’t do what they were supposed to do,'” Freeh said. “It requires using a tool that is in some ways imperfect.”

His office is working to publish this year’s report in the next week, and at least 5% of the properties mandated to respond still have incomplete profiles — which means the final assessment of Philadelphia’s carbon footprint might not be quite right.

Does anyone have a better system? Freeh said other cities, like Chicago, hire a third-party reviewer to check the data for inaccuracies.

But it’s a useful estimate anyway, he said.

“It’s important to keep in mind what the goal is,” Freeh said. “When we’re talking about reducing our carbon footprint, this is a big step toward that.”