Millions of iPhone owners who updated to Apple’s latest operating system over the last six months may have noticed that their phones are charging a little slower than usual since they did so. For that, they can thank the climate change activists at Apple’s Cupertino, California, headquarters.

Apple installed a new feature on those phones — Clean Energy Charging — and automatically signed up all users for the service. When activated, the feature allows users to reduce their carbon footprint by charging the phone more slowly when renewable sources of energy, such as solar or wind power, are not widely available on the electric grid.

“When Clean Energy Charging is enabled and you connect your iPhone to a charger,” Apple says, “your iPhone gets a forecast of the carbon emissions in your local energy grid and uses it to charge your iPhone during times of cleaner energy production.”

Apple included the option in the latest update to its operating system, iOS 16.1, released in October. It was included without warning or much in the way of notice, and the updated iPhones are automatically signed up for the option. To turn it off, users have to be aware of what is going on, and wade deep into the iPhone settings in order to turn it off.

Apple touts it as a feature. Many users, who might have been as to baffled why their phones weren’t charging very quickly, are calling it a bug. Apple says the option is only available on iPhones in the United States.

Many iPhone users who updated months ago were caught unaware when alerted about the new feature in a Twitter post over the weekend. Many reported that when they attempted to turn off the feature, a pop-up tried to dissuade them from doing so by reminding them yet again that clean energy charging reduces their carbon footprint.

The CEO of a thermal energy company, a self-avowed clean energy enthusiast, Tim Latimer, said on Twitter Sunday that he was glad Apple is working on dynamic charging to shift to low carbon hours, “but the way they rolled it out isn’t great. Limited awareness, default position is opted in. We should demand better transparency and choice for clean energy solutions or it’s going to backfire.”

Marjorie Taylor Green, the bombastic Republican congresswoman of Georgia, bragged that she turned off the feature Sunday in order to increase her carbon footprint. “I believe in feeding trees,” she wrote, above an illustration of the role carbon dioxide plays in photosynthesis.

Congressman Chip Roy of Texas also mocked Apple’s attempt to force its climate concerns on customers who spent a thousand dollars for their iPhones. “Don’t forget to plug in your 2 Electric Vehicles! (equivalent to 20 household refrigerators),” he wrote. “And don’t ask where the iphones were made or rare earth materials sourced from!”