Science Technology The 7 Best Energy-Efficient Air Conditioners of 2021 Stay cool and feel good with these sustainable units. By Amber Nolan Amber Nolan College at Brockport, State University of New York Amber Nolan is a freelance writer for Treehugger who is passionate about sustainable living, nature, and outdoor adventure. Learn about our editorial process Updated July 9, 2021 Share Twitter Pinterest Email Science Space Natural Science Technology Agriculture Energy Our editors independently research, test, and recommend the best products; you can learn more about our review process here. We may receive commissions on purchases made from our chosen links. MangTeng / Getty Images The Rundown Best Overall: Lennox XC25 at Lennox.com This central air unit cools and maintains room temperature for ultimate energy savings. Runner Up: Amana AVXC20 at Amana-hac.com Earning an EnergyStar most efficient rating, this central air unit is quiet and effective. Best Budget: Keystone KSTAW05CE at Walmart Affordable yet extremely energy efficient, the Keystone can drastically reduce energy bills. Best Portable: Whynter ARC-14SH at Walmart Easily mobile, the Whynter ARC-14SH has several additional features to reduce its environmental impact. Best for Small Rooms: Frigidaire 6,000 BTU Window-Mounted Air Conditioner at Walmart For rooms between 150 and 250 square feet, the Frigidaire is an excellent choice. Best Window: LG Electronics 14000 BTU Dual Inverter Window Air Conditioner at Ajmadison.com This smart window unit is compatible with Alexa and Google Home. Best for Large Rooms: Senville SENA-24HF/Z Mini Split Air Conditioner at Amazon This mini split unit is mounted to the wall and can cool up to 1,450 square feet. Modern consumers’ love affair with air conditioners is conflicting. They provide relief from summer heat and allow us to live comfortably, and save lives in hot regions and during heatwaves. But they also harm the environment by contributing heavily to planet-warming pollution in two major ways ways. First, air conditioning units require a lot of energy to operate, and until all the electricity supplied to our homes comes from clean sources, flipping on the AC means burning fossil fuels. Second, many air conditioners historically use hydrofluorocarbons, which become a powerful greenhouse gas if they leak during repair or disposal of the device. When it's time to get rid of an old air conditioner, it's important to dispose of it properly. The good news is that manufacturers are developing alternatives to hydrofluorocarbons and other new ways to make air conditioning more sustainable, but there’s still a long way to go. Today, one of the biggest differences you can make when shopping for a new AC is looking for a unit that requires less energy. The most efficient units now consume about 30% less electricity than standard units, helping to slice your electric bills and reduce carbon emissions. You can also cut carbon emissions by deploying some low-tech tricks to cool your home, to keep the AC turned off just a little longer. These air conditioners are leading the way charge in energy-efficient options currently on the market. Best Overall: Lennox XC25 View On Lennox.com For an ultra-efficient central air conditioning unit, it’s difficult to top the Lennox XC25. Rated most efficient by EnergyStar for 2020, this air conditioner has an outstanding SEER rating of 26 thanks to its advanced technology. While many central units have one or two stages with one steady speed or two speeds (low and high), the Lennox XC25 is designed with multiple, precise speed adjustments in a range of 1% increments. This allows temperatures to remain consistent, even when the unit cycles on or off. The unit also controls humidity, with different moisture levels removed based on the climate (normal regions, dry areas, or coastal), and produces around 50 decibels of sound, making the XC25 significantly quieter than similar units. Understanding Energy Ratings Before choosing an air conditioning unit, review the advice from the experts at EnergyStar in order to properly maximize its use. There are three major efficiency ratings to consider: EER, CEER, and SEER. Energy Efficiency Ratio (EER) measures how effectively a cooling system operates, with a rating of 12 considered to be a good EER. Combined Energy Efficiency Ratio (CEER) is the standard for window units set by the Department of Energy in 2014, which factors in energy during use (EER) and standby power. Seasonal Energy Efficiency Ratio (SEER) is for central air conditioners and measures efficiency over an entire season. Individual room air conditioners do not have a SEER rating like the central air units, but they do have EER and/or CEER rating. The higher the rating, the more efficient the unit. Air conditioners can also have a BTU (British Thermal Unit) rating, which measures how much heat is removed from the air. A higher BTU rating indicates a more powerful device. Runner Up: Amana AVXC20 View On Amana-hac.com With a SEER rating of up to 24.5, the Amana AVXC20 is a high-quality, quiet central air conditioner that can help to drastically reduce a home's energy bill if it's time to replace an older unit. Specialized inverter technology allows the power and speed levels to be automatically adjusted to use less energy when reaching the set thermostat temperature (so the compressor doesn’t have to be working harder than it needs to). The unit includes an extensive warranty. The AVXC20 earned EnergyStar’s most efficient rating for 2020. Stay Cool With The Best Energy-Efficient Fans Best Budget: Keystone KSTAW05CE View On Walmart View On Amazon View On Home Depot Highly energy-efficient air conditioners are typically more expensive, but the EnergyStar-rated Keystone KSTAW05CE is a budget-friendly way to stay cool while keeping energy consumption low. The 5,000 BTU window unit is surprisingly quiet and has various energy-saving options like sleep mode, three cooling and fan speeds, and an energy-saving mode. For added convenience, there’s also a programmable thermostat, LED display, timer and a remote control. The Keystone’s CEER rating is 12.1, making the average yearly cost around $40 to run. While the air conditioner is a great value, it’s not ideal for larger rooms. Best Portable: Whynter ARC-14SH View On Walmart View On Amazon Easily mobile, the Whynter ARC-14SH has several additional features to help reduce its environmental impact, plus it also has a heater, dehumidifier and fan (however, a cooling-only version is available). The 14,000 BTU unit can cool up to 500 square feet and recycles moisture during the cooling process through its auto drain technology. It also uses R-32 refrigerant that allows for 10% less energy consumption that other refrigerants. The air filters can be easily washed when dust or debris collects, helping to improve air quality. The Whynter includes an exhaust hose, window kit, and remote control with a timer function to help conserve energy. Best for Small Rooms: Frigidaire 6,000 BTU Window-Mounted Air Conditioner FFRE063ZA1 View On Walmart View On Amazon Finding the right air conditioner to match the size of the room is important, and bigger air conditioners aren’t always better. A larger unit in a smaller room will keep more humidity inside, leaving a sticky feeling in the air. For rooms between 150 and 250 square feet, the Frigidaire Energy Star 6,000 BTU is an excellent choice. Reasonably priced, this 110-volt window unit has an energy efficiency rating (EER) of 12.1, with temperature and fan settings easily adjusted by remote control (or the main panel). There’s also a sleep function, auto function, three cooling speeds, and 24-hour timer. Best Window: LG Electronics 14000 BTU Dual Inverter Window Air Conditioner with Wi-Fi Control View On Ajmadison.com With dual inverter technology, the LG 14,000 BTU window air conditioner has a CEER rating of 14.7, is up to 25% more efficient than the EnergyStar requirements, and was the recipient of the EnergyStar 2018 Emerging Technology Award. In addition to being efficient, the unit is quieter than most (just 44 decibels) and costs about $68 per year to run. Controlled by a remote, touch panel, or through Google Assistant and Amazon Alexa, adjusting the air conditioning settings is simple–even when you're on the go. The LG unit uses R32 refrigerant and can cool up to 800 square feet. Best for Large Rooms: Senville SENA-24HF/Z Mini Split Air Conditioner View On Amazon View On Senville.com Mini splits are another popular cooling option, and they also switch to heating when the temperature drops. They typically have a space-saving, ductless design, which is mounted to an exterior wall to exchange heat from indoors to outdoors or vice versa. The SENA-24HF is an excellent mini split that's available to DIYers with a SEER rating of 20.5, and it has the capability of cooling a room between 1,200 and 1,450 square feet. EnergyStar certified, the 24,000 BTU unit also has heating (for the cooler months), dry, and turbo modes. To top it off, it’s WiFi enabled (or controlled by remote) and compatible with Google Home. Other features include self-cleaning, a built-in dehumidifier, remote-controlled thermostat, and refrigerant leak detection. Installing a mini-split is a pretty big job, because the refrigerant tube must travel through your wall from the exterior unit to the interior air handler, and the unit needs to hard-wired to your home's electrical system. If you're not comfortable doing those jobs yourself, consider getting a quote from a licensed installer. Final Verdict Our top choice is the Lennox XC25 for the new advancements in technology that make the unit extremely efficient (view at Lennox). If you need a portable option, our pick is the Whynter ARC-14SH, perfect for medium-sized rooms, it will also significantly cut down the electric bill for even more savings (view at Amazon). Why Trust Treehugger? The author of the article, Amber Nolan, resides in South Florida and conducted extensive research on air conditioners before purchasing her own energy-efficient window unit. Once your air conditioning is installed, but sure to check out our Treehugger's tips for making the most of it.