It’s hotter in Baltimore than it’s been all year. Parks and streets are quiet as residents find refuge from triple-digit heat next to cranked-up air conditioners.

All that energy has to come from somewhere, and to meet increased stress on the grid, power plants must churn extra juice. But there is another side to that equation: reduced demand. Sometimes, including this week, energy grid operators provide financial incentives for big users to power down.

Among those users now will be Baltimore’s two pro sports stadiums. The Maryland Stadium Authority agreed this month to potentially reduce power when requested — and earn between $50,000 and $100,000 each time, according to authority spokesperson Rachelina Bonacci.

This strategy, called “demand response,” is increasingly essential as the country faces a growing energy quandary.

The authority’s contract is with Enel North America, a demand response provider working with the region’s grid operator, PJM Interconnection. Occasionally, the authority will be asked to curtail usage of its chiller plant, an integral component of the the HVAC systems that cool M&T Bank Stadium and Oriole Park at Camden Yards.

As extreme heat saturates the outdoors this week, residents are bracing for sky-high bills from Baltimore Gas and Electric Company. And the grid has been reacting, too.

On Monday, PJM recorded its highest peak electricity demand since 2011 and called on some users to curtail usage both on Monday and Tuesday, PJM spokesperson Dan Lockwood said.

That doesn’t necessarily include the stadiums. Lockwood said PJM would not name participating customers, and Bonacci did not reply when asked whether the authority had received a request to curtail.

This week is not optimal for Camden Yards to reduce its chiller plant usage, as the Orioles are playing at home. The authority, which owns the two stadiums, plans to only do so when the complex is idle.

That means fans likely won’t notice any change in power at the ballpark (although Jackson Holliday provided plenty of hitting power Monday). But on other occasions, when a heat wave lines up with no events, the authority could earn easy cash.

“No free lunches, I live by that,” Jeffrey Provenzano, the authority’s vice president for facilities, said during an early June board meeting. “But maybe this is a free lunch.”

The approach is similar to an airline overbooking a flight. If a company sells more tickets than it has seats on a plane, it cannot immediately generate more seats, but it can incentivize passengers to take a later flight.

PJM Interconnection works with Enel, an intermediary, to pay facilities to relieve strain on the grid during essential moments. This can prevent ratepayer bills from skyrocketing even further and avoid the use of peaking power plants, which only operate during high demand periods and often have higher emission rates.

The concept of demand response is often described as a “virtual power plant” since decreasing usage has the same balancing effect as turning on new, hypothetical energy generation.

“You can create a nuclear power plant’s worth of customer response,” said Abe Silverman, a sustainable energy researcher at Johns Hopkins University, “and that’s amazing.”

Provenzano said the authority had been approached about reducing power at the stadiums, which both opened in 1990s, in recent years, but previously declined. Now, though, the authority could be in for an increased payday.

Energy is more valuable than ever, which means demand response customers are earning substantially more than they were a few years ago, Silverman said.

Hundreds of new customers have reached a deal with Enel this year to curtail their usage because of the increase in compensation.

The build-out of energy-hungry data centers and increased electrification, combined with the retirement of key power plants, has caused an “energy crunch,” as Silverman put it, and rising prices. And while it costs more to power up when the grid is at max capacity, it also means larger payouts to power down.

PJM is “massively incentivizing participation,” Molly Jerrard, Enel’s head of demand response, said, with a “clear price signal.”

Enel’s demand response customers range from Gillette Stadium, home of the New England Patriots, to the Busch Gardens amusement park in Williamsburg, Virginia. In Maryland, Wicomico County Public Schools partners with Enel and earns $120,000 annually for demand response.

Facilities are alerted via text or email and, sometimes, with strobe lights installed on-site. In the authority’s case, the Baltimore stadiums will be given between 30 minutes and two hours of notice to curtail energy; if they do not, there is no financial penalty, but they might not be invited to participate and earn that “free lunch” in future years.

If they continue to participate, they’ll receive annual payments from PJM via Enel.

It’s unclear if those payments would stay with the authority or be passed along the teams, but Provenzano described demand response as a “good payday for the stadium authority.”

“There is no risk as we can decline any request; for instance we do not want to participate hours before an event,” Provenzano wrote in a memo obtained through a public records request. “The only potential penalty would be removal from the program as a result of too many requests declined.”

While reducing energy to the chiller plant, the authority would use an ice vault to temporarily cool the stadiums.

PJM, which services all or parts of 13 states, including Maryland, is the nation’s largest grid operator. Electricity demand is expected to surge in the coming years, and this summer, which already surpassed expectations, is approaching PJM’s record.

Its largest-ever summer load came in 2006, with over 165,000 megawatts (equivalent to 94 Calvert Cliffs nuclear plants). PJM’s peak Monday was over 160,000 MW, which approaches that high-water mark and is substantially more than the grid had projected for this summer’s peak.

Demand response has been around for decades, but the increasing thirst for energy makes it especially crucial.

“Rather than overbuild the grid with expensive and polluting peaker plants that take years to come online, demand response is an important part of modernizing the grid to be more dynamic and sustainable,” Jerrard said in a statement.

Silverman described the concept of turning off energy on an incredibly hot day as “fundamental to the conservation movement.”

“The cleanest electricity,” he said, “is the electricity that you don’t use.”