Spanish experts break down the true cost of running fans and air conditioning overnight as heatwaves persist

The fear of the bill

Summer after summer, Spanish households wrestle with the same dilemma: stay cool and risk a punishing electricity bill, or endure the heat. A 2026 survey by Samsung Climate Solutions found that 62 percent of users run their air conditioning less than they would like, purely out of fear of the cost. At the same time, a report by Create shows that 77 percent of Spanish homes budget for better cooling, and 39 percent buy a ceiling fan during the first few months of the year instead of waiting for the first heatwave. Those early purchases suggest that many consumers are trying to avoid the air-conditioning bill altogether.

A floor fan consumes about 50 watts. If you run it for eight hours every night throughout July, the total comes to 12.4 kilowatt hours. That’s much less than most people think.

The inverter advantage

Technician Carlos Llul points to the most common mistake: switching the air conditioning on and off repeatedly. A room at 29 degrees Celsius cooled to 24 will make the unit work hard at first. Once the target temperature is reached, an inverter model automatically reduces power. Turning the machine off at that moment means the room heats up again, forcing another full-power start later. Llul stresses that modern inverter units do not run at 100 percent all night.

Here lies the biggest mistake, because modern inverter equipment does not consume at full power all night long.

For a demanding scenario with a 1,500-watt machine, Llul estimates that eight hours of cooling can cost roughly one euro of electricity. That single figure, he hopes, will ease the anxiety that leads people to switch off their units.

The thermostat trap

Setting the thermostat to 19 or 20 degrees to cool the home faster is another widespread error, according to Gemma Reinón, a lawyer with Català Reinón Abogados. The appliance does not speed up; it simply works longer and consumes more. Reinón recommends a setting of around 25 or 26 degrees, especially when paired with light clothing, lowered blinds and good air circulation. The IDAE, Spain’s institute for energy diversification, backs this advice and notes that every one-degree reduction can increase cooling costs by roughly 7 percent. The goal, adds lawyer Jordi Català, is not to turn a home into a refrigerator.

The objective is not to turn the house into a fridge, but to maintain a bearable thermal sensation without forcing the equipment to work at maximum for hours.

Practical habits that cut consumption

The experts converge on a short list of free or cheap habits. Lower blinds during the hottest hours, ventilate the house at night, and keep filters clean. The expert behind the TikTok account @EnergiaJusta underscores that a split air-conditioning unit typically draws between 1 and 1.3 kilowatts, meaning even a few hours of midday use is far less expensive than the folklore suggests. All of them stress that the real consumption depends on outdoor temperature, insulation, window exposure to the sun and the contracted electricity tariff, so the numbers cannot be transferred blindly from one home to another.

A change of mindset

Together, the calculations point toward a small but meaningful shift in how Spanish families manage summer nights. The fan, at a negligible cost, remains the cheapest option for those who can sleep with moving air but no active cooling. An inverter air conditioner left on at a steady, moderate setpoint costs more but, at roughly one euro per night, is still a manageable sum for most households. The advice from all four sources returns to the same core principle: fight the heat with sensible temperature targets and maintenance, not by turning the unit into an on-off switch driven by bill anxiety.