In 2006, a record-breaking heatwave pushed New England's power grid to its limit. A decision made years later is now saving people up to $149 million during extreme summer heat

A record-breaking heatwave nearly two decades ago exposed just how vulnerable New England's electricity grid was during scorching summers. On August 2, 2006, temperatures in Massachusetts climbed to 99°F with 65% humidity, prompting residents to switch on air conditioners and fans at unprecedented levels. The surge in electricity demand set an all-time record on the regional power grid.

At the time, New England already had some of the highest electricity prices in the United States. But what happened in the years that followed has now become a powerful example of how long-term clean energy investments can pay off.

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How rooftop solar transformed New England after 2006

Around 2008 to 2010, New England states began investing heavily in rooftop solar panels. Falling hardware prices, supportive state policies, and expensive electricity encouraged thousands of homeowners to install solar systems on their roofs.

Nearly two decades later, those investments are delivering major financial benefits.

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According to a new report from the Acadia Center, distributed rooftop solar played a critical role during the June 28 to July 4 heatwave, generating more than six gigawatts of electricity and helping save electricity customers an estimated $130 million to $149 million over the course of the week.

Solar generated more electricity than nuclear during peak demand

One of the report's most surprising findings came on July 2, when rooftop solar systems delivered more electricity to the regional grid than New England's nuclear power plants during the afternoon.

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The report estimates that solar arrays saved between $39 million and $54 million in a single day.

At certain points, rooftop solar supplied around 25% of the region's total electricity demand, significantly reducing pressure on the grid during one of the hottest days of the year.

Why rooftop solar made such a big difference

Unlike large solar farms, rooftop solar—often called "behind the meter" generation—first powers the homes and businesses where it is installed. Any extra electricity is automatically sent to the local grid, helping nearby buildings meet their energy needs.

That local generation becomes especially valuable when electricity demand spikes.

"The grid soaks it up," and that means "other resources don't have to burn during those hours of production," saving other ratepayers money because they don't have to buy those other fuel sources, said Jamie Dickerson, senior of climate and clean energy programs at the Acadia Center.

He added, "Between 2 p.m. and 7 p.m. on that hottest day of July 2, the distributed solar actually contributed more to the fuel mix than the region's nuclear fleet."

According to Dickerson, "Basically, we saw between 28% and 43% of daily costs were avoided by the distributed solar in the region."

Solar also helped reduce peak electricity demand

Dickerson explained that rooftop solar works because it generates electricity close to where people actually use it.

"It's distributed solar, it is close to where the load is, you know the actual electricity consumption, that means that it effectively reduces the peak demand that is seen on the regional grid," he said.

Regional grid operator ISO New England also reported that installed solar capacity can reduce electricity demand by more than 1,700 megawatts during normal weather conditions.

The organization noted that growing rooftop solar generation has even shifted the region's peak summer electricity demand away from the hottest part of the afternoon toward the early evening.

Solar saved more than $1 billion last year, report says

The benefits of rooftop solar extend well beyond a single heatwave.

According to the Acadia Center, solar energy saved New England electricity customers between $1.26 billion and $1.37 billion last year alone.

Dickerson said the investments are becoming increasingly valuable as hotter summers become more common.

"If we hadn't invested in these resources, we would have been even more exposed and overexposed to the fuel sources that are more volatile and more subject to the dramatic swings in prices during peak periods," he said.

He also added, "These are resources that we've invested in that are there and will show up on the grid during these types of hotter summers and El Niño summers. We're going to see savings year-round, but especially in the summer with higher temperatures that we're seeing."

Energy efficiency also helped lower electricity bills

The report found that rooftop solar was not the only reason customers saved money during the heatwave.

Other energy-efficiency measures—including better insulation, weatherization, and more efficient appliances—also reduced electricity demand.

According to the analysis, these passive efficiency measures saved customers between $94 million and $97 million during the week, including about $29 million on July 2 alone.

Dickerson acknowledged that it can be difficult to measure savings because researchers must estimate what electricity costs would have been without rooftop solar.

Still, he hopes the findings challenge the idea that clean energy drives up electricity prices.

"This is hopefully helping to make the argument that these are not only good for all of our public policies around emissions reductions, but also good economic energy affordability policies too," Dickerson said.

As debates continue over future clean energy investments, the report suggests that decisions made years ago are now helping New England residents keep electricity costs lower during some of the hottest and most demanding days of the year.

(With TOI inputs)