This article is from The Spark, MIT Technology Review's weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

The unending heat this summer has kept the air conditioners in my apartment windows wildly busy. When I’m not taking guesses about what my electric bill might look like this month, I’ve been thinking a lot about how air-conditioning is the double-edged sword of climate technologies. 

On one hand, temperatures are rising around the globe, shattering extreme heat records on basically every continent. That’s making air-conditioning less of a “nice to have” and more of an absolute necessity in some parts of the world. 

On the other hand, air-conditioning is becoming a monster when it comes to energy demand. We might have to add a whole US electrical grid’s worth of new energy generation just to power all the air conditioners that will come online in the next few decades. 

This dynamic is heating up along with the planet, so for the newsletter this week, let’s talk about the climate problem/solution that is air-conditioning. 

Cold take

Air-conditioning seems ubiquitous where I live in the US, to the point that I carry around a sweater in the summer in anticipation of over-cooled offices and restaurants. 

But in many parts of the world, including some of the countries at highest risk for extreme heat, most people go without it. Roughly 5% of households in India have air-conditioning. Of the 2.8 billion people living in the hottest parts of the world, roughly one in 10 has access to AC, according to the International Energy Agency. 

That’s expected to change in the coming decades, as the world’s largest AC manufacturers target growing markets in Asia and Africa. By 2050, over two-thirds of the world could have an air conditioner, and half those units will likely be in three countries, according to the IEA: China, Indonesia, and India.

Wider access to cooling is absolutely essential: it will save lives as heat waves become more common and more extreme because of climate change. But adding more air conditioners presents a challenge, because they’ll increase energy demand—by a lot. 

Space cooling makes up nearly 40% of all expected growth in energy demand between now and 2050. 

In 2018, cooling consumed about 2,000 terawatt-hours of energy globally. In 2050, that could grow to 6,200 TWh. The difference, 4,200 TWh, is roughly the same amount of energy the entire US electrical grid supplied in 2022. So if things don’t change, we’ll need to build enough renewable energy not only to replace all the fossil fuels still on the grid, but also to power a metric boatload of air conditioners. 

Hot off the press

The good news is that there’s a ton of room for improvement in air-conditioning technology. 

I spoke about this with Ankit Kalanki, who recently helped run a massive competition called the Global Cooling Prize. He’s also a manager in the program on carbon-free buildings at the Rocky Mountain Institute, a nonprofit energy think tank.

The Global Cooling Prize wrapped up in 2021 and awarded prize money to teams from academia and industry that came up with better ways to cool buildings. The target was a cooling system that produced one-fifth the climate impact of conventional air conditioners while meeting a host of other criteria. 

There were eight finalists with a range of approaches, some improving on existing technology and some looking for entirely new ways to do cooling. 

The two winning teams built better versions of existing air conditioners, which are called vapor-compression systems. By swapping out certain parts for better ones (more effective heat exchangers, variable-speed compressors, and so on), the teams were able to come up with a much more efficient version of the air conditioners that we know and love today. 

But several of the other finalists were looking to mix up how we cool buildings. While these didn’t reach the climate target or one of the other criteria, all of them had “very interesting, innovative approaches,” Kalanki says. 

A few of the finalists belong to a category of startups looking to materials called desiccants, which can suck up moisture from the air like a sponge. By using these materials to deal with humidity, cooling devices could greatly reduce electricity use while keeping us comfortable on hot days. 

I just took a close look at these desiccant cooling systems for my latest story. Basically, there’s a long way to go before these materials find their way into homes and commercial buildings, but the physics behind how they might work is fascinating. If you’re interested in hearing more, check out my reporting for all the details. And for more on both the impending problem of air conditioners and some potential solutions, check out some other stories from the Tech Review vault. 

Related reading

I wrote last summer about the summer heat waves in Europe, and what adding more air-conditioning could mean for the continent.

My colleague James Temple reported in 2020 about how big a problem AC was shaping up to be.

James also took a look at how caloric materials, which can release heat when they’re subjected to pressure or an electric field, could chart a new method of cooling buildings.  

Keeping up with climate

Texas and California have historically faced a stressed grid in the summer. This year, however, things have so far been quiet for the two states. California’s had a lot of hydropower capacity because of an excessively wet winter, and Texas has installed a ton of solar recently. (Wall Street Journal) 

Some experts say that paying people to use less energy during high-stress times on the grid could help keep blackouts at bay, but Texas hasn’t put any residential demand-response programs in place. (Canary Media)

Geothermal startup Fervo reached a new milestone, completing a 30-day demonstration of its 3.5-megawatt commercial pilot plant. (Bloomberg) 

→ Fervo showed earlier this year that it can use its wells as a massive underground battery. (MIT Technology Review)

The hottest new corporate climate trend is “greenhushing,” or keeping quiet about climate pledges. Nobody can ask questions about your goals if you never talk about them. (Grist) 

While agriculture has struggled in some parts of the world, crop yields are still on the rise in the US. Experts aren’t sure how long that trend will last. (Modern Farmer)

The US federal government has been pumping money into clean energy since the Inflation Reduction Act passed nearly a year ago. More than a third of the manufacturing funding has gone to South Korean companies, which have positioned themselves as key partners, especially in batteries. (Inside Climate News)

Intense storms are causing severe flooding around the world. Climate change is playing a role in these storms, and we’re only going to see more of them. (Vox)