Heat in the home: Which air conditioner is better?

In the first half of 2026, Germany saw a surge in demand for air conditioners, with approximately 387,000 portable units sold, more than double the number from the previous year. This increase comes amid rising heatwaves that have driven consumers to seek cooling solutions. However, while these affordable options appear cost-effective upfront, they often result in significantly higher electricity bills due to their inefficiency. The German consumer organization Stiftung Warentest has highlighted that some of the cheapest models consume more than twice the energy required by more efficient alternatives. Portable air conditioners, known as monoblock units, are considered the most accessible and quickest solution for home cooling. These devices consist of a single indoor unit that can be manually moved between rooms using wheels. They operate by drawing heat from the room through a thick exhaust hose connected to a window or door. In Germany, such units start at around 270 euros. While convenient, they suffer from several drawbacks. Their operation relies on a closed-loop refrigeration system, similar to other air conditioning systems, but the design leads to inefficiencies. One major issue is the temperature rise caused by the hot exhaust hose returning heat into the room. Additionally, many installations lack proper sealing, allowing warm air to re-enter through gaps in windows or doors. The vacuum effect created within the room further exacerbates this problem, drawing in warmer outside air. As a result, these units are less effective at maintaining cool temperatures compared to fixed installations. According to Stiftung Warentest, they consume over twice the amount of electricity needed for cooling compared to more efficient models. The inefficiency of portable units poses additional risks, particularly in homes equipped with gas heaters. The vacuum effect can allow carbon monoxide, a colorless and odorless gas, to seep into living spaces, potentially leading to poisoning. A recent case in Vienna highlights this danger, prompting experts to advise against using monoblock units in such environments without professional inspection. Energy costs for cooling a 70-square-meter apartment using a portable unit can reach up to 320 euros annually. For those seeking a more efficient alternative, split-system air conditioners offer improved performance. These units feature separate indoor and outdoor components connected by a two-meter-long refrigerant line. Like portable units, they can be installed without professional help, though they require access to an open window or door for the refrigerant line. Unlike monoblock units, split systems do not create a vacuum inside the room, making them safer to use alongside gas heating systems. According to Stiftung Warentest, the annual electricity cost for a tested split unit is around 230 euros, which is notably lower than that of portable units. Fixed installation air conditioners represent the most efficient and comfortable option for homeowners and tenants alike. These systems include both indoor and outdoor units, typically mounted on rooftops, balconies, or building facades. The refrigerant lines are permanently installed and must be filled and sealed by professionals to ensure optimal performance. Fixed units are generally quieter and more reliable than portable or split systems. The initial cost ranges from 400 to 2,500 euros, with installation bringing the total to between 800 and over 5,000 euros. For rental properties, landlords must approve the installation of fixed air conditioning systems, whereas property owners have greater flexibility. These systems provide consistent cooling, reduce noise levels, and minimize energy consumption. With increasing awareness of energy efficiency and safety concerns, many consumers are beginning to prioritize long-term savings and comfort over the immediate affordability of portable units. As the climate continues to shift, the demand for more sustainable and efficient cooling solutions is likely to grow.