Jorge Morales de Labra, an industrial engineer and director of Próxima Energía, has challenged a persistent belief about air conditioning in Spanish homes: that keeping a unit running for hours is more efficient than switching it off when it is not needed. In a typical home, he says, there is no reason to leave the air conditioner running just to avoid the energy used when it restarts.
As temperatures rise, air conditioning becomes part of daily life in many Spanish households, but operating time and thermostat settings can quickly affect electricity bills. Morales de Labra estimates that running a unit for eight hours can cost more than €10 a day, depending on the appliance and electricity tariff. That figure is not universal: another consumer estimate puts eight hours of operation at 25-26°C at roughly €0.60-€1.20 per night, or €18-€36 over 30 days, based on the price and equipment assumptions used in that calculation.
Why Switching Off Can Save
The widespread belief that an air conditioner uses so much energy at startup that it should be left on has led some households to cool rooms even when nobody is using them. For a standard household unit, Morales de Labra advises switching it off when cooling is no longer needed, rather than keeping it on to avoid a restart. Household costs mainly depend on how long the appliance runs and the temperature it is asked to maintain; actual consumption varies with the unit, insulation, room size, solar exposure, outdoor conditions and tariff.
Modern inverter systems add an impressive technical distinction: instead of repeatedly switching between full power and off, they can adjust compressor output to maintain the selected temperature. That internal adjustment is different from switching the appliance off when a room is no longer in use. Cooling an empty room so cannot be justified by confusing inverter operation with the energy involved in restarting a switched-off unit.
Morales de Labra also stresses the value of reducing heat entering the home before relying on cooling. For a room exposed to direct sun throughout the day or afternoon, he recommends installing an awning. Lowering blinds during the hottest hours and closing shutters can also reduce heat gain. These measures cut the cooling load and the time the compressor needs to run.
Lowering the thermostat far below the usual setting will not cool a room faster; it simply gives the system a colder target. The practical approach is to use cooling when needed, choose a moderate temperature and avoid running the unit continuously in an unoccupied space.
Different Systems, Different Rules
Climate-control systems do not all work the same way. Some water-based systems or systems with greater thermal inertia may need different management because they take longer to reach the desired temperature. Standard household air conditioners can generally be operated flexibly, while inverter models adjust their output as conditions change.
Timers, automatic modes, ECO functions and app-based controls can help match operation to occupancy and routine. Their value depends on the model and how it is used; the basic goal is to avoid unnecessary cooling rather than keep a unit running at all times.
Recommended Temperatures and Smart Features
Temperature settings are another basic factor. Spanish energy-efficiency guidance reported by RTVE recommends keeping indoor air conditioning between 24°C and 26°C and says each degree below that range can add about 7% to 10% to consumption. The Instituto para la Diversificación y Ahorro de la Energía (IDAE) is cited in Spanish guidance recommending a summer setting of around 26°C or higher. Morales de Labra has suggested approximately 23°C as a reasonable setting. The recommendations differ, but all indicate that a lower thermostat setting increases cooling demand. The right setting also depends on comfort and household circumstances.
Reporting on Morales de Labra’s advice estimates that each additional degree of cooling can raise electricity use by roughly 7%, illustrating how a substantially lower target can increase consumption. It is also advised to keep the indoor-outdoor temperature difference within 12 degrees. When available, ECO mode can adjust the unit’s operation to help maintain comfort while limiting consumption.
For nighttime use, the automatic shut-off function can prevent unnecessary operation after occupants fall asleep. When buying a new unit, a higher energy-efficiency rating may cost more upfront but can reduce running costs over time. Any potential savings depend on the appliance, usage pattern, home and electricity tariff.
As Spain faces another hot summer, Morales de Labra’s advice gives households a practical way to stay cool without overspending: reduce heat entering the home, choose a moderate thermostat setting and align air-conditioning use with actual occupancy. Cooling costs vary, but leaving a unit on in an empty room solely to avoid restarting it is not a sound energy-saving strategy.
