Summer air conditioning: the ENEA guide to improve comfort and reduce consumption

Before using the air conditioner…

The first action to take is to exploit the characteristics of your property by adopting passive cooling solutions to reduce energy needs upstream. It is therefore essential to balance three key factors: temperature, humidity and air quality.

Calabrese specifies: “All openings towards the outside of the house must be screened to block the sun’s heat and the steam created inside the house must be immediately eliminated. Before starting to cook or take a shower it is very useful to open the window to take advantage of the natural air currents or alternatively turn on the electric extractor, keeping it running for at least ten minutes after finishing. The immediate extraction of the steam prevents the air from becoming saturated and the humidity from spreading into the other rooms. Ventilation of rooms and air exchange also contribute to ensuring healthy indoor air, reducing the concentration of domestic pollutants and excess humidity”.

A natural ally, also in this sense, is indoor greenery. Thanks to the natural processes of transpiration and shading, plants in internal environments contribute to mitigating temperature and humidity in the apartment, optimizing any energy consumption of air conditioners: “through evapotranspiration or evaporative cooling, plants remove heat from the environment in a natural way, reducing the thermal loads that the air conditioning system must dispose of”, continues Calabrese.

To increase the perceived coolness it is necessary not to separate the pots but to create small groups of plants in the areas where you spend the most, in order to generate a more stable and fresh microclimate. Plants are also useful for creating a solar barrier: if positioned in front of windows they act as natural shields, blocking the sun’s rays before they heat up the rooms: “this allows us to reduce the amount of external air to be introduced and thermally treated, promoting energy savings”, concludes Calabrese (the study on indoor greenery was carried out in collaboration with Rosita Romeo, CasaClima consultant, expert in living comfort, and our author).

If these measures are not enough, the second move is the fan. This device does not lower the temperature of the environment, but moves the air, creating a cooling effect on the skin, which – with minimal electricity consumption – can make it feel up to 3°C less. Only as a last resort, therefore, will we proceed to turn on the air conditioning, but adopting some measures to maximize environmental benefits, comfort and energy savings. Let’s see ENEA’s recommendations:

1. Regular maintenance

To function correctly, the air conditioner requires cleaning and maintenance, always keeping the refrigerant circuit pipes under control, which it is essential to thermally insulate. The electricity consumption of a machine that works under stress due to lack of maintenance reaches up to 30% more than the factory parameters. In addition to the energy aspect, it is important to underline that mold and bacteria that are harmful to health, including legionella bacteria (which can be deadly), more frequently nest in air filters and fans of unmaintained internal units.

It is important to also maintain the external unit, keeping the grills and fans clean from dust, leaves, pollen and smog which can accumulate over time and reduce the efficiency of the system. The legislation provides for the obligation of a system booklet and periodic checks for systems with a power greater than 12 kW for summer ones and 10 kW for winter ones.

2. Technology and energy class

The choice of air conditioner is important to reduce consumption and reduce costs on the bill. Regardless of the technology chosen, for lower consumption and CO2 emissions, models with an energy class higher than A are preferable (the energy label for air conditioners for domestic use has been mandatory since 2003 – Directive 2002/31/EC).

For split-type air conditioners, in addition to the energy efficiency class, both the seasonal energy efficiency index “SEER”, in cooling mode, and the seasonal performance coefficient “SCOP”, in heating mode are shown on the label: the higher these values ​​are, the greater the efficiency of the machine. To meet the need to label increasingly efficient appliances available on the market, from 1 January 2019 the scale from A+++ to D is mandatory: for example, a class A+++ model will consume up to 40% less electricity than a class B one.

Air conditioners with an inverter control system are particularly functional when you plan to keep the air conditioning on for many hours at a time. They are more expensive than those equipped with on-off technology, but they have lower energy consumption, reduced noise and guarantee greater comfort within the environments served.

The maximum economic advantage can be obtained by combining the system with a photovoltaic system. In this case it is essential to synchronize the operation of the air conditioner with the productivity of the system, which is maximum during the central hours of the day.

3. Incentives

For purchases made by 31 December 2026, the so-called air conditioner bonus allows you to benefit from a tax deduction of up to 50%. Here is a summary table of the rates:

4. Internal and external location

During the installation phase it is important to place the internal unit in the upper part of the wall: the cold air tends to descend and will mix more easily with the hot air which tends to rise. Avoid placing the air conditioner behind sofas or curtains because the barrier effect blocks the diffusion of fresh air. It is also advisable to ensure that the external unit is not exposed to the sun and bad weather and to leave sufficient free space around the appliance (at least 30-50 cm) for correct air circulation. Plants that are too close together, improvised covers, objects placed in front of grills and fans or installations in too small and closed spaces can compromise correct functioning and increase energy consumption.

5. Doors and windows

To block the heat before it enters, it is recommended to completely lower the shutters or close the shutters on windows exposed to the sun during daylight hours. In fact, the entry of new hot air into the room forces the equipment to carry out additional work to bring the temperature and humidity back to the required levels, with a consequent waste of energy. It is advisable to open the windows during the cooler hours of the night, if the air conditioning is not running.

6. Temperature

The legislation states that during the summer season the internal temperature must not fall below 26 degrees centigrade, but comfort is often also guaranteed by a higher temperature (two or three degrees lower than the external temperature), and to avoid the feeling of oppressive heat, activating the “dehumidification” function may be enough, as the humidity present in the air makes the temperature perceived to be much higher than the real one.

7. One split per room

It is useless to install a more powerful air conditioner in the corridor hoping that it will cool the entire house: the only result will be to catch a cold every time you cross the corridor going from one room to another, as it will be the only room that will be cooled. If the system is equipped with multiple splits, it is advisable to turn on only those that are really necessary, avoiding cooling unused rooms and keeping the doors of the air-conditioned rooms closed to limit the loss of fresh air.

8. Heat inputs of the equipment

During the hottest hours it is advisable to limit the use of equipment that contributes to increasing the internal temperature of the home (such as computers, televisions, household appliances, lights).

9. Cooling programs and consumption monitoring

Adjust the thermostat to a comfortable temperature, setting cooling programs that optimize energy consumption at night or when you are not at home. These functions allow you to both increase comfort and minimize the time the appliance is turned on. Furthermore, they allow you to turn the air conditioner on and off even remotely and keep it running only for the period of time in which you really need it. For example, the “night” or “sleep” function adjusts the room temperature to respond to changes in body temperature during sleep.

Today, many air conditioners also allow you to monitor the operation of the system via apps or smart thermostats. These tools allow you not only to control times and methods of use, but also to verify daily and monthly energy consumption, helping to identify any waste and possible inefficiencies of the system. In this way it is possible to recognize anomalous situations due to malfunctions and adopt more sustainable behaviors.

10. Certification and diagnosis and energy

In recent years, SIAPE has collected over 7.3 million Energy Performance Certificates (APE) for the residential sector. This means that more and more citizens have a useful tool at their disposal to evaluate the overall performance of the property and the related estimated consumption. Regarding the hot season, the APE contains a simplified graphic evaluation of the summer performance quality of the building, which allows you to understand at a glance how much the building envelope is able to protect the rooms from the summer heat.

If you want to delve further into the causes of your property’s consumption, it is advisable to have an energy diagnosis of the building carried out by a qualified professional. This study allows us to evaluate in detail the state of the thermal insulation and the real efficiency of the air conditioning systems, suggesting the targeted interventions to be carried out on the basis of a precise cost-benefit ratio. In addition to reducing summer air conditioning costs by up to 40%, these structural interventions are even more convenient if you take advantage of the tax deductions in force for the energy requalification of buildings.