Air conditioners can feel like nothing short of a godsend at the height of summer, but as climate change drives temperatures higher and income growth increases AC adoption, air conditioning could become as much of a problem as it is a solution. In a new study on AC adoption trends, researchers found that air conditioning adoption is likely to boom over the rest of this century, eventually driving residential electricity usage up 83 percent. The study is being published today in Proceedings of the National Academy of Sciences.

"This is gonna cost a lot of money."

Air conditioner adoption is in many ways a good thing — it's no secret that a cooler home will make living there more pleasant — but it also leads to some big issues. More air conditioners mean more energy needed to run them, and more electricity being made means more greenhouse gases going up into the air. "I think this is a huge challenge," Lucas Davis, an Associate Professor at UC Berkeley's Haas School of Business and lead author of the paper, tells The Verge. "This is just a huge challenge for electricity markets, for electricity systems, for electricity infrastructure. This means an enormous increase in the need for electricity generation and transmission. This is gonna cost a lot of money." And that's money that will need to come from developing countries, which will drive AC growth.

Davis and his co-author, Paul Gertler, a professor at UC Berkeley's Haas School of Business, looked at billing data from over 25 million Mexican households to determine how temperature increases drove air conditioning use. They saw that, relative to a day between 65 degrees and 70 degrees Fahrenheit, monthly electricity consumption rose 3.2 percent for every day the weather went above 90 degrees.

The study also looks at how rising incomes across the globe will lead to more households with air conditioning. Looking at a smaller data set of 27,000 households, the researchers saw that air conditioning ownership is near zero in cooler areas, regardless of income. In hotter areas, however, AC ownership grew by 2.7 percent for every additional $1,000 in annual household income.

"We had kind of vaguely known that this was a big deal, but until we looked at it, I didn't realize how big of a deal this really is," Davis says. "That's because air conditioners use a lot of electricity."

More energy means more emissions

At current levels of air conditioner ownership, residential energy usage may only increase around 15.4 percent by the end of the century. But once you factor in what will likely be the dramatic growth of air conditioning, the end-of-century estimate shoots up to an 83 percent increase. That's nearly double the amount of residential energy use overall — not just the energy used by air conditioners.

The researchers believe these findings apply not just to Mexico, but globally. In part, that seems to be because their study somewhat duplicates earlier research, which has come to similar conclusions. But even if the study isn't entirely novel, "their finding is still very relevant — as not so many have appreciated the consequences of this," Detlef van Vuuren, an environmental change professor at Utrecht University who was not involved with the study, tells The Verge in an email.

Because of the growing energy use, AC adoption will likely lead to a "huge increase" in carbon dioxide emissions, Davis says, feeding climate change.

Van Vuuren, who has done previous research on air conditioner adoption, believes that climate change could actually even out the effects of growing AC costs. "Additional warming in warmer areas is most likely also accompanied by warming in cold areas, leading to less heating demand," he writes. "In the first part of the century, actually the reduced energy consumption for heating dominates." The increased energy consumption from air conditioners won't hit until the second half of the century, he's found; though energy usage would only even out on a global level, not necessarily in individual countries.

"We should be celebrating this."

Davis doesn't necessarily see that happening, however. Because income growth will lead to so many people buying their first air conditioners over the next 80-or-so years, the increased energy usage is likely going to be huge nonetheless. "You could keep temperatures exactly the same," Davis says, and you'd still see that huge increase in air conditioner ownership and electricity usage.

That's likely to start in current middle-income countries; Davis names Brazil, Mexico, and China, where AC adoption is already skyrocketing — sales have doubled there over the last five years, with China's 2013 AC sales reaching eight times the total sold in the US. "Next you go to places like Indonesia, Philippines, Nigeria," Davis says. "I'm talking about places that are a little lower income than Mexico, Brazil, and China, but that are very hot." India, which due to its larger population and hotter climate could reach 12 times the cooling demand of the US, will likely hit later in the century, too. (In the US, where air conditioning is already widespread, increased adopt is unlikely to be an issue.)

"We should be celebrating this. This is people being more comfortable," Davis says. "But let's be clear: this is gonna require an enormous increase in electricity infrastructure." So while there's an obvious climate change element to this finding — growing carbon dioxide emissions as electricity use rises — the bigger story to Davis is how that demand will be met.

Citing others' research, Davis says these infrastructure costs will quickly run into the trillions. That could change, however. "As sales of air conditioners increase, that creates incentives for manufacturers of air conditioners to find ways of making them better, and that includes more energy-efficient air conditioners," Davis says. The increased adoption will likely lead to less electricity usage and carbon dioxide emissions because of the market's response. "How much technological change will there be?" Davis asks. "That's a huge question that's hard to answer."