What temperature should the air conditioning be set to for heating?

What temperature should the air conditioning be set to for heating and cooling?

The ideal air conditioning temperature depends on whether the unit is being used in heating mode during winter or cooling mode during summer. In general, the most sensible approach is to avoid extremes and maintain a stable, breathable environment rather than asking the system to produce the greatest possible difference from the outdoor temperature.

For heating at home, the most useful reference is usually between 20 and 22 °C during the day. At night, many homes find a gentler setting more comfortable, especially in bedrooms. For cooling in summer, the recommended domestic range is generally between 24 and 26 °C. The exact setting depends on activity, humidity, insulation, sunlight, room size, ventilation, bedding, and the thermal sensation of the people in the room.

Raising or lowering the thermostat excessively does not make the air conditioner heat or cool faster. It simply gives the unit a more demanding target, causing it to work for longer and increasing electricity consumption. The best result usually comes from asking the system for exactly the temperature that is needed, distributing the air correctly, and allowing it to operate steadily.

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Recommended air conditioning temperatures at a glance

What temperature should the air conditioner be set to for heating?

Heating with air conditioning works best when it is set moderately. In homes, the most sensible range is usually between 20 and 22 °C during the day, with small variations depending on activity, humidity, and the home’s insulation.

This range is normally enough for a dining room, office, or living room with normal occupancy. In a very cold apartment, a home with large windows, or a property with poor thermal protection, a somewhat higher setting may be necessary. In a well-insulated home, a lower setting can sometimes provide the same sensation of comfort.

At night, the reference drops a little. To sleep with a heat pump or a split system in heating mode, many homes find a balance between 15 and 17 °C in the bedroom, although the comfortable range depends on bedding, ventilation, and the actual thermal sensation. This is a reference for gently preparing or maintaining the room, not an instruction to create an excessively cold bedroom or to keep the unit working aggressively all night.

The key is not to push the unit, but to let it distribute warm air without creating an annoying draft. A moderate setting, low or automatic fan speed, and correctly positioned louvers usually produce a more even result than selecting a very high temperature.

Why a higher heating setting does not warm the room faster

An air conditioner in heating mode does not work like a traditional radiator. It takes energy from outside and moves it indoors through the reversed refrigeration cycle. When it is set to a temperature that is too high, the system does not magically speed up; it simply works longer to reach a target that the room may not actually need.

In practice, that can mean more noise, higher consumption, and a less stable sense of warmth. The unit may initially operate at high power when it detects a large difference between the actual room temperature and the selected target, but entering a much higher temperature does not necessarily improve the speed of the initial warm-up. It mainly prolongs intense operation.

The idea of looking for the perfect heating temperature should therefore not focus on pushing the air conditioner to its limit. The objective is to achieve a stable and breathable environment. A living room at 21 °C with reasonable humidity can feel more pleasant than another at 23 °C that is unevenly heated, because comfort does not depend only on the number shown on the remote.

The radiation from walls, the direction of the airflow, the activity taking place in the room, the temperature of the floor, and the quality of the building envelope all affect how warm the room feels. Efficiency does not come from asking more of the unit, but from asking exactly enough.

What temperature should the air conditioner be set to in summer?

In a shut-up home at midday, the air conditioner remote often turns into a thermometer of quick decisions: lower it without thinking, wait for the unit to work magic, and then assume a higher bill. The most reliable reference for summer at home falls between 24 °C and 26 °C, a range that balances comfort, health, and energy use without overburdening the system.

In practice, 24 °C can work well in living rooms and more occupied spaces, while 25 °C or 26 °C is often a better fit for bedrooms or areas where people sit more and move less. A room exposed to direct afternoon sun may require a slightly lower setting than a shaded room, but the difference should be approached carefully.

The key is not to chase the coldest possible temperature, but to maintain a stable sensation. Lowering the thermostat too much does not cool faster; it simply forces the system to work longer to reach a more demanding target. On extremely hot days, that target may even be unrealistic for the unit or the building.

A shaded room with good sealing may feel comfortable at 26 °C, while another room bathed in afternoon sun may need 24 °C to create a similar sensation. The orientation of the dwelling, the height of the building, humidity, sunlight exposure, insulation, room size, and the number of people present all play a role.

The difference between the indoor and outdoor temperature

During summer, when the street temperature rises well above 35 °C, it is advisable to avoid jumps of more than 12 °C relative to the indoor temperature. A larger contrast can be uncomfortable for the respiratory system, dry out the air, and increase the feeling of thermal shock when going in and out of the house.

Comfort in air conditioning is more like a gentle slope than a cliff: the more abrupt the change, the harder it is for the body to tolerate. The same general principle applies in winter. A room at 21 °C can feel comfortable even if it is raining outside, windy, or the sidewalk is frozen. The body usually appreciates a smooth transition rather than a sudden leap between the street and the living room.

This margin is particularly relevant for sensitive people, older adults, and small children, who may notice temperature changes more strongly. It is also useful to remember that the thermostat measures the air near the unit, while the body experiences the temperature of the entire room, including walls, floors, furniture, and air movement.

Why setting the unit to 18 °C is usually a bad decision

Turning the thermostat down to 18 °C in summer does not make the room cool faster. The unit does not produce cold faster simply because it receives a lower instruction; it works until it reaches that more demanding target. The result is a compressor that runs longer, higher electricity consumption, and in many cases air that is too dry or too cold once the target is finally reached.

The same logic applies in heating mode. Setting the unit to 18 °C does not make the room heat faster either. It may be a reasonable temperature for some circumstances, but it is not an aggressive heating instruction. If the intention is to warm a room quickly, selecting an unnecessarily high temperature does not improve the unit’s fundamental heating capacity; it only extends the time required before the system considers the target to have been reached.

There is also a physical effect that explains why an excessive difference between outdoors and indoors can feel worse than expected. It can dry out the air and cause discomfort in the throat, nose, or joints. Comfort does not improve by turning the room into a small artificial winter in summer or an overheated enclosure in winter. Often the opposite happens: an imbalanced feeling appears, especially if the airflow points directly at the sofa, desk, or bed.

Efficiency data help put the summer issue into perspective. Various technical and educational references on climate control indicate that each degree lower can increase consumption by around 7% or 8%. Between setting 24 °C and 21 °C, the cumulative increase in cost can be around 21%. On a summer bill of 80 or 90 euros, that difference is no longer an abstract theory: it can translate into several euros more each month, and over the whole season the impact is clearly noticeable.

The exact percentage is not universal because consumption depends on the machine, the climate, the building, the selected fan speed, the hours of use, and the condition of the filters. Nevertheless, the pattern is clear: the farther the setting is from the actual comfort temperature, the more the system works.

Comfort is more than a number on the display

The temperature shown on the remote does not explain everything you feel in a room. Relative humidity, airflow, solar radiation, ventilation, insulation, and the temperature of the surrounding surfaces influence comfort just as much as the number on the display.

Two rooms at 25 °C can feel very different if one has stagnant air and the other enjoys a gentle, even current. Similarly, two homes at 21 °C can feel opposite if one is well insulated and the other leaks heat through windows, shutter boxes, or poorly sealed doors.

In winter, excessively dry air can make 20 °C feel less pleasant, while moderate humidity helps the room feel warmer. In cold and dry climates, reducing airflow a little or using the unit more gently sometimes gives better results than increasing the set temperature without restraint. In summer, a humid environment feels heavier even if the thermometer does not show a particularly high value. In those conditions, the air conditioner does more than cool: it dehumidifies, and that noticeably changes how the temperature feels.

The body experiences the environment as a whole, not as an isolated number. This is why the ideal setting is not identical in every home. The right temperature comes from the combination of variables rather than from a rigid figure repeated without nuance.

How to direct the airflow in heating and cooling mode

Airflow direction when cooling

Cold air is denser than warm air, so it tends to sink. In summer, the louvers should generally be directed upward or at least away from the people occupying the room. This allows the cool air to spread better throughout the space and avoids a direct blast onto sofas, beds, or work tables.

A constant stream of cold air on the body can cause discomfort in the throat, neck, or muscles. It may also make the room feel colder in one area while other areas remain stuffy, encouraging people to lower the thermostat unnecessarily. Correcting the airflow direction often pays off more than continuing to push the temperature downward.

Airflow direction when heating

In heating mode, warm air tends to rise. The flow should therefore be directed downward or, at least, should not remain stuck near the ceiling. If warm air is blown too high, it takes longer to descend to the area occupied by people.

Good louver direction helps distribute energy better and avoids the feeling of a warm ceiling and cold floor, which is quite common in large rooms. A ceiling fan or standing fan can also help move the warm air accumulated in the upper part of the room back through the occupied zone.

In both modes, the ideal distribution is an ordered, gentle flow rather than a straight, persistent line aimed at the body. Air conditioning works better when it creates an even environment instead of a burst of air going in and out.

The practical temperature for each room

Living room

The living room is usually the room that best shows the difference between theory and reality. People, lamps, screens, sofas, visitors, and sometimes large windows all come together there.

For heating, between 21 and 22 °C usually offers a reasonable balance for watching television, reading, or receiving visitors without feeling a blast of heat when getting up from the sofa. For cooling, 24 °C or 25 °C is often a solid base.

If the room receives direct sun in the afternoon, the thermal sensation can rise by one or two degrees even if the thermostat stays where it was. In summer, a room exposed to direct sun may need a slightly lower setting, but it is usually more efficient to lower blinds and curtains first rather than immediately choosing an extreme temperature.

Bedroom

A bedroom does not necessarily require the same temperature as a living room. For heating, many homes find a reference of 15 to 17 °C useful when the unit is used to warm the room before bedtime. The goal is not to sleep at that exact temperature all night, but to avoid turning the bedroom into a sauna before getting into bed.

For summer cooling, many homes work better between 25 and 26 °C, while the broader reference for sleeping is usually 25 to 27 °C. The final choice depends on the person, bedding, humidity, and room temperature. Excessive cooling is usually counterproductive.

Bed orientation also matters. If the air falls directly onto the sheets, the thermal sensation changes drastically and the body may get colder than intended. The sensible approach is to let the airflow circulate through the room without hitting the sleeping area directly.

Home office

The home office deserves a special mention. A working body generates heat, but the mind also appreciates stability. An environment around 21 °C in heating mode usually avoids both drowsiness and excessive bundling up.

For cooling, the reference can drop slightly to around 24 °C, especially if there is a computer, printer, several screens, or more than one person present. Electronic equipment adds internal heat, even if it often goes unnoticed. A workspace that seems moderate can become stuffy within a few hours if several devices are operating.

If the desk is next to an exterior wall or under a window, it is worth observing how the sensation changes throughout the day before increasing or decreasing the setting out of habit. Air conditioning in an office not only provides comfort; it can also help sustain concentration when the room becomes too warm.

Kitchen

The kitchen generates its own heat from ovens, stoves, and appliances. In heating mode, such a space may require a lower setting, usually around 20 or 21 °C, to compensate for that extra heat load.

In summer, cooking can make the room feel hotter than the rest of the home. Even so, it is often more efficient to use ventilation, close the kitchen off from the rest of the house when appropriate, and reduce the heat produced by appliances where possible instead of setting the air conditioner to an extreme.

Large rooms and poorly distributed spaces

A larger space takes longer to stabilize and needs more careful air distribution. Lowering the temperature further is not always the solution. Improving internal circulation may be enough for the room to feel even.

Large rooms can also develop vertical differences in heating mode, with warm air near the ceiling and cold air close to the floor. In cooling mode, poorly positioned airflow can leave some areas too cold and others still stuffy. Correct louver positioning and gentle circulation can be more effective than changing the thermostat by several degrees.

Heating mode, insulation, and humidity

Thermal sensation does not come only from the thermostat. Two homes at 21 °C can feel opposite if one is well insulated and the other loses heat through windows, shutter boxes, doors, ceilings, or exterior walls. Warm air, like water, finds cracks. When a home loses heat easily, the unit enters longer cycles and the environment becomes less uniform.

There are homes where the feeling of cold comes more from a freezing wall than from the air itself. In those cases, raising the thermostat does not solve everything. A thicker curtain, sealing a window, or closing an unused room can provide more comfort than two extra degrees on the remote.

The air conditioner works on the air; the house, on the other hand, is also made of surfaces that absorb and give back cold or heat. A poorly sealed home forces the system into a constant battle against the outdoors, while a building that holds energy better can remain comfortable with a more moderate setting.

Humidity has a similar impact. Excessively dry air can make 20 °C feel less pleasant, while moderate humidity helps the room feel warmer. In summer, high humidity makes the air feel heavy and can make people lower the temperature more than necessary. Since cooling also removes moisture, a moderate setting can sometimes become comfortable once the humidity falls.

Comfort and efficiency often go hand in hand when the environment is balanced. If the room feels uncomfortable, first check humidity, drafts, direct sunlight, wall temperature, and air distribution before changing the thermostat dramatically.

Cooling mode, sunlight, and ventilation

In summer, close doors and windows while the unit is running. Lower blinds and curtains during the hottest hours of sunlight, particularly when windows face the afternoon sun. Ventilate first thing in the morning or at night, when outdoor temperatures drop, rather than allowing hot air into the home during the middle of the day.

These are simple measures, but they make a difference. The home keeps cool better and the system does not have to compensate for constant losses. In air conditioning, losing less usually saves more than cooling more.

During the middle of the day, heat enters through windows, walls, and ceilings, making this period demanding for both the home and the air conditioner. Anticipating the heat by cooling moderately before the house becomes excessively hot is usually more efficient than trying to correct a room that is already loaded with heat.

Avoiding direct sunlight also protects the comfort of bedrooms and living rooms. A shaded room with good sealing may remain comfortable at 26 °C, while an exposed room may feel much warmer at the same setting. The remote cannot compensate efficiently for every source of solar heat if the building is left open to it.

Night mode and undisturbed rest

At night, the body does not need the same environment as during full activity. Sleeping in excessive heat disrupts rest, but a stream that is too cold can also interrupt sleep. This is why night mode, available on many units, is useful.

In heating mode, the gentler reference is often close to 15 to 17 °C in the room if the system is being used to warm it before bedtime. The objective is not to maintain a high temperature all night, but to create a moderate environment without excessive noise, dryness, or direct airflow.

In summer, the temperature for sleeping is usually between 25 and 27 °C, with small variations depending on the person, bedding, and room humidity. Many bedrooms work well at 25 or 26 °C when the air is distributed properly.

Night mode gradually reduces intensity, softens the noise, and prevents the room from cooling or heating too much during the deepest hours of rest. Very dry air, a direct blast, or a noisy compressor can disturb sleep more than the temperature itself.

A timer adds another layer of common sense. Programming shutoff or a gradual decrease after the first part of the night reduces consumption and prevents the unit from running unnecessarily during the hours when the body is already at rest. In a small bedroom, a slightly higher setting and minimal ventilation usually work better than a low setpoint with high fan speed.

The best nighttime setting is usually the most discreet one, not the most ambitious. The airflow should circulate through the room without falling directly onto the bed. A more enveloping, diffuse distribution is better than a straight and persistent current.

Why the right setting improves energy efficiency

Keeping the heating range between 20 and 22 °C and the cooling range between 24 and 26 °C is usually much more effective than chasing an extreme setting. These ranges reduce unnecessary compressor operation and help maintain a stable temperature.

When the target is excessively demanding, the unit may run for longer periods, consume more electricity, produce more noise, and create greater temperature differences between areas of the room. In summer, forcing very low temperatures can also lead people to turn the unit on and off repeatedly because of discomfort. That back-and-forth worsens thermal stability and makes consumption less predictable.

Efficient use is almost silent: let the machine maintain a comfortable, steady range, like turning down the heat on a stove so a sauce does not split. A moderate setting does not mean tolerating discomfort; it means avoiding the false idea that an extreme setting buys time.

Use ECO mode when available

If the air conditioner includes an ECO mode, it can adjust operation to reduce consumption without completely breaking the feeling of coolness. It is particularly useful when the room is already close to the desired temperature and does not need maximum output.

Use timers and smart thermostats

If the home stays empty for much of the day, there is no point in keeping the same setting for hours. A timer or a smart thermostat can reduce unnecessary operation and bring the temperature closer to the actual presence of people.

The benefit is not only financial. Programming the system avoids the back-and-forth of entering a room that is too hot or too cold and then selecting an extreme temperature to correct it. The system can begin heating or cooling before people arrive, allowing it to work progressively.

Consider time-of-use electricity tariffs

The cost of using air conditioning depends not only on the selected temperature, but also on when it is turned on. In time-of-use tariffs, off-peak hours offer the lowest electricity price, especially during the night and early morning.

This does not mean suffering through heat or cold simply to use a cheaper tariff. It does make sense to understand that the clock is also part of home efficiency. Setting the unit so the bedroom is already cool before bedtime, or so comfort is restored at dawn, can provide comfort at a somewhat lower cost.

The hours of lowest energy demand often coincide with the early morning or the first hours of the day. During those periods, the electrical system is under less pressure and prices tend to be softer in contracts with different time bands. By contrast, the middle of the day is usually more demanding for both the grid and the home, particularly during a summer heatwave.

Fans can improve the result

Ceiling or standing fans can complement the air conditioning without competing with it. In heating mode, they move the air accumulated in the upper part of the room and distribute it more evenly, making it possible to stay comfortable with a somewhat more moderate setting.

In cooling mode, a fan can improve the sensation of air movement and help distribute cool air through the room. The difference may seem small, but it becomes visible at the end of the month when consumption has not increased because of excessive thermal demand.

A fan does not lower the actual room temperature in the same way as an air conditioner, but it can improve the perceived temperature by moving air across the skin. It should be used carefully so that it does not create an irritating draft or blow directly onto people while they sleep.

Maintenance affects the selected temperature

Cleaning the filters is a decisive factor in both heating and cooling. A dirty filter makes air circulation harder and forces the unit to work more. That layer of dust acts like a scarf on the system: it may not be visible from outside, but it hurts performance.

Checking the filters regularly improves efficiency, helps preserve air quality, and reduces breakdowns caused by continuous use without maintenance. Dirty coils, dusty components, or clogged drains can also penalize performance. A unit that cannot breathe properly consumes more to deliver the same result.

Cleaning and checking the system during seasonal changes is not a decorative task. It is a way to preserve the air conditioner’s real heating and cooling capacity without forcing the compressor or increasing the unit’s noise.

The same logic applies to old or inefficient units. If a device has been running for years with weak performance, it can end up costing more than it seems. A system with inverter technology, better compressor control, and higher energy efficiency maintains temperature better and consumes less. Technology does not replace good use, but it gives good use room to breathe.

Common mistakes in heating mode

Setting the temperature too high

Many people enter the house cold and immediately set the heating to 24 or 25 °C, hoping for quick warmth. That gesture may be valid in a very large or poorly insulated home, but in most households it creates excessive heat, a dry atmosphere, and higher-than-necessary spending.

A living room at 20, 21, or 22 °C may become comfortable once the air is distributed evenly and the cold surfaces are addressed. Before selecting a much higher target, check whether curtains, doors, windows, or unused rooms are allowing heat to escape.

Using the unit like a radiator

Air conditioning in heating mode needs time and circulation. If it is turned on and off frequently, it works with less stability and loses some of its efficiency. Maintaining a moderate setting for a reasonable period usually gives a more even temperature and a more pleasant sensation when walking around the house.

Ignoring cold surfaces and drafts

When the sensation of cold comes from a freezing wall, a poorly sealed window, or an exterior door, increasing the thermostat may not solve the underlying issue. A thicker curtain, sealing a gap, or closing an unused room can provide more comfort than two additional degrees on the remote.

Common mistakes in cooling mode

Setting the unit too low from the beginning

One of the most common mistakes is setting the air conditioner to the minimum as soon as a heatwave begins, as if this bought time. The unit does not produce cold faster because the number is lower. It simply works longer to reach a much more demanding final temperature.

Leaving doors and windows open

Keeping doors open, forgetting to lower blinds in full sun, and allowing hot outdoor air into the home all add to consumption. The air conditioner then has to compensate for constant losses instead of maintaining the room efficiently.

Relying only on the number on the remote

A poorly aimed unit may cool unevenly, leaving some areas too cold and others still stuffy. This increases the temptation to lower the temperature further, when the real problem is distribution. Correcting the airflow direction often pays off more than continuing to push the thermostat downward.

Neglecting filter cleaning

Allowing filters to remain dirty for weeks makes air circulation harder, reduces the unit’s capacity, increases electricity use, and can contribute to breakdowns. Regular maintenance is especially important during periods of continuous summer or winter use.

Regulations and reasonable limits in Spain

In public spaces and shared-use buildings, regulations set clear limits. In Spain, Royal Decree-Law 14/2022 established energy-saving guidelines affecting climate control in certain settings.

For summer cooling, the general limit in many public buildings and publicly accessible spaces should not go below 27 °C. In winter heating, the temperature should not generally exceed 19 °C.

These are references intended to reduce consumption and emissions, not to dictate the ideal comfort level inside every private home. Domestic use is more flexible, but the spirit is similar: avoid extremes. Setting the unit to 20, 21, or 22 °C in heating mode, or to 24, 25, or 26 °C in cooling mode, provides a reasonable base for many households.

A home in northern Spain does not need the same setting as one in an area with mild winters. A large family does not use a home in the same way as a couple who spend few hours there. The regulation provides an energy framework; the practical setting must still reflect the building, the climate, and the people using the room.

How room use changes the ideal setting

Not every room calls for the same temperature. A kitchen can generate heat while cooking, a living room can gain warmth from people and electronic equipment, and a bedroom may require less airflow because its occupants are inactive.

A living room occupied by several people accumulates more body heat than an empty bedroom during the day. A kitchen may need a different setting if cooking is taking place. A home office with a computer, printer, several screens, or more than one person can become warmer than expected over several hours.

Solar exposure also changes the result. A bright living room at midday may work well at 20 °C in heating mode, while the same space at night may call for 22 °C to provide the same feeling. In summer, a shaded room may remain comfortable at 26 °C, while a sunlit room may need 24 °C.

The useful temperature changes with use. Smart home air conditioning does not treat the unit as an inflexible referee; it adapts the system to the rhythm of the home.

A reasonable strategy for heatwaves and cold spells

In a heatwave, the temptation to lower the air conditioner to the minimum appears almost automatically. However, the most robust answer remains the same: set it between 24 and 26 °C, adjust the airflow, keep the home closed off from the sun, and let the system work steadily rather than forcefully.

Anticipating the heat is usually better than waiting until the room has become excessively hot. Moderate cooling before heat has entered through windows, walls, and ceilings allows the system to stabilize the space more efficiently.

When the outdoor thermometer drops, the house does not necessarily need more degrees indoors. A room at 21 °C can feel very comfortable even when it is raining, windy, or freezing outside. If cold walls or drafts are the real problem, sealing windows, improving curtains, closing unused rooms, and distributing air correctly may help more than increasing the thermostat.

The most sensible approach in either season is to protect the home from external losses, use a stable setting, avoid direct airflow, and maintain the unit. That combination better protects health, avoids overspending, and keeps the home at a reasonable comfort level.

The right temperature is a balance, not an extreme

The most useful answer is often also the least spectacular. For most homes, heating mode works best between 20 and 22 °C during the day, with a gentler setting at night, especially in bedrooms. In summer, cooling mode generally works best between 24 and 26 °C during the day, with 25 to 27 °C often being more suitable for sleep.

The rest depends on the home and its actual use. The room, insulation, humidity, sunlight, room size, airflow, and the way the property retains energy can do more for comfort than a three-degree increase or decrease.

A good setting is not noticed for being excessive, but for the absence of discomfort: no sudden drafts, no cold feet, no freezing walls, no stuffy air, no dry throat, and no skyrocketing bills. That is the sign that the system is working for you rather than against you.

In air conditioning, the right number is almost never the highest or the lowest. It is the one that allows you to live with light clothing, sleep without surprises, and keep the house at a calm and stable temperature. The ideal number is not a technical whim; it is a boundary of balance between comfort, the bill, health, and care for the equipment.