When Heat Becomes Deadly: The Importance of Next

As climate scientists predict 2023 to be the world's hottest year, people are bracing for heat waves around the world. More countries are facing extreme temperatures that pose a threat to human health, including higher humidity levels, which hinder the amount of moisture that can escape from the human body into the surrounding air. This sweat helps cool the body, and rising humidity levels are becoming a growing concern in many parts of the world.

To confront this heat and humidity and maintain a thermally comfortable indoor environment in their homes, more people are exploring the market for new air conditioners. And although most consumers still make their purchase decisions by looking at the sticker price, energy- and sustainability-conscious consumers are looking at labels and performance ratings to guide them in buying a high-efficiency AC that will save energy, money, and reduce carbon emissions. But do labels and performance ratings give a true picture of what consumers should expect?

High humidity levels are devastating for human health and productivity as they inhibit the ability of sweat to evaporate creating even more life-threatening conditions.

AC testing standards that specify the test procedures and calculating methods for performance ratings have evolved significantly over the past three decades. The AC industry has continuously optimized efficiency levels of their products to meet these standards by pushing innovations across heat exchanger design, inverter compressor technology, and better controls. Additionally, policy measures such as labeling programs and minimum energy performance standards have been put in place in several countries to help consumers differentiate between less efficient air conditioners and high-efficiency ones. As a result, high-efficiency units that are two to three times more efficient than entry-level products are available on the market today.

However, a key challenge remains with the AC testing standards and performance rating systems. They are limited in what they measure, particularly in the context of a warming world with rising humidity levels. These standards are more aligned with the climate profiles of the global north, which experience lower levels of humidity than those in the global south. Further, the current test procedures are too simplistic — they measure the AC's standard cooling capacity by locking the compressor speed at an outdoor temperature of 35°C (95°F), far from how the units operate in the real world.

Because these test procedures are not aligned with real-world operation, we are missing out on a major opportunity to improve AC efficiency. This impact of inadequate testing standards is even more critical in hot and humid regions of the world, which expect rapid growth in demand for air conditioning. RMI analysis suggests that adoption of typical AC products sold on the market today would contribute to cumulative emissions of over 100 gigatons of CO2 equivalent by 2050 — more than twice the total worldwide greenhouse gas emissions today.

Adoption of typical AC products sold on the market today would contribute to cumulative emissions of over 100 GT of CO2 equivalent by 2050 — more than twice the total worldwide greenhouse gas emissions today.

The Global Cooling Prize, led by RMI; the Department of Science & Technology, Government of India; and Mission Innovation; selected and piloted two winning room air conditioning (RAC) technologies that performed at much higher efficiencies in real-world settings. The winning technologies shattered the performance ceiling of what was previously believed to be possible — achieving dramatically lower electricity consumption of over 75 percent compared to the baseline unit (a fixed-speed, mini-split unit — the most commonly sold room air conditioners in the Indian market) — even on days of extreme temperature and humidity while maintaining the indoor space below 27°C and 60 percent relative humidity.

Not only are the winning technologies dramatically more efficient than typically sold products on the market, but they are also up to two times more efficient than today's best available high-efficiency AC products. However, to catalyze a market transition to these super-efficient next-generation ACs and for them to be recognized by consumers, the current testing standards must measure all aspects of real-world operation that are missing today.

If you are an AC user living in a hot and humid place such as Mumbai or Chennai in India, Singapore, or Florida in the United States, you almost always turn down the thermostat or the AC setpoint significantly to manage humidity in the air. This results in overcooling of the air and consequently higher-than-expected energy consumption. And while you expect to save energy and money because you purchased a high-efficiency AC, your energy bills are not going to be dramatically different than a typical product.

This is because current AC testing standards are not designed to assess efficiency in dealing with high humidity. Future standards must recognize the improvement in efficiency resulting from better humidity management and shift away from the idea of using temperature as a proxy for thermal comfort.

Another key area that future standards must incorporate is accurately assessing the performance of AC under its native controls (instead of locking the compressor speed as mentioned earlier in this article) and at partial-load operation. Variable-speed ACs that use inverter technology can offer significantly higher savings than their fixed-speed counterparts by operating in a steady state during low cooling demand periods (instead of cycling on and off).

But we cannot have super-efficient next-generation ACs without updating the current testing standards and performance rating systems. And this triggers a vicious loop where consumers will not demand next-generation AC products due to lack of visibility into their performance, and manufacturers will have little to no incentive to develop and bring these products to market due to low demand and unclear efficiency targets from policymakers.

We need essential updates to the AC testing standards and performance rating systems that recognize products that are designed for real-world operation.

In a warming world where rapid urbanization and rising incomes will drive a significant demand for cooling, we need to accelerate a market shift to these next-generation ACs that are better for the environment and economy and will save consumers money. It's a win-win scenario for everyone.

A coalition of RMI, Lawrence Berkeley National Laboratory's Global Cooling Efficiency Program, and CEPT University, India, has embarked on an initiative to develop Performance Metrics for Characterization of Next-Generation Room Air Conditioners, with support from the Clean Cooling Collaborative. The goal of this initiative is to develop a pragmatic hypothesis that can inform the future AC testing standards and performance rating systems for super-efficient next-generation room ACs. This will give manufacturers a more complete target to design for, while ensuring that this shift does not add a substantial burden in terms of cost, complexity, and infrastructure on third-party test labs and manufacturers. For consumers, this will enable them to make better-informed purchasing decisions that simultaneously provide cooling and cost savings while reducing climate pollution.

We encourage the standard-setting bodies, AC industry associations, and AC manufacturers to come together and demonstrate their leadership at this critical moment to confront the climate crisis and provide people with healthy, comfortable, and productive indoor environments.