The same question comes up every summer: is air conditioning going to send the electricity bill through the roof? The answer depends mainly on three things: the unit's technology, its energy label, and how you actually use it day to day. Let's go through each one.
Inverter vs. on/off: the difference that matters most
A traditional on/off unit runs at full power until it hits the set temperature, switches off completely, then starts up again at full power as soon as the temperature creeps up. Every restart draws a spike of electricity.
An inverter unit continuously adjusts the compressor's speed, matching output to what's actually needed at any given moment instead of cycling on and off in jumps. The practical result: it holds the temperature far more steadily and, over extended use (running all day, or for weeks at a stretch in a second home), consumes noticeably less than an equivalent on/off unit. It's now the standard in practically all residential units being installed today.
The energy label: from A+++ to G
Every air conditioning unit sold in the European Union carries a mandatory energy label, on a scale running from the most efficient classes down to the least efficient. The more efficient the class, the less electricity the unit uses to deliver the same cooling power. When comparing two units with the same BTU rating, always check the label — the consumption difference between a high class and a low class adds up, especially for units that will run many hours a day through summer.
The temperature you choose matters more than you'd think
Spain's Institute for Energy Diversification and Saving (IDAE) recommends not going below 26°C in summer as a reference for sensible cooling use. Every degree below that reference forces the compressor to work harder to maintain the gap with the outdoor temperature, and that extra effort translates directly into higher consumption — especially on the hottest days, when the gap between indoors and outdoors is already large.
A simple trick: pairing air conditioning with a ceiling or standing fan lets you raise the set temperature by a degree or two without losing the feeling of coolness, because moving air helps your body perceive less heat at the same temperature.
A dirty or badly sized unit uses more electricity
Two very common causes of extra consumption that have nothing to do with the unit's technology, but with its condition and whether it was sized correctly from the start:
- Dirty filters or a blocked outdoor unit: force the unit to work harder to move the same amount of air, gradually pushing up consumption without you noticing until the bill arrives. We cover this in detail in our preventive maintenance and cleaning service.
- A unit that's the wrong size for the room: both an underpowered unit (which never reaches the set temperature and runs flat out constantly) and an oversized one (which short-cycles on and off) use more electricity than necessary. Check our guide on how many BTU you need to see whether your unit is correctly sized.
Simple habits that make a real difference
- Lower blinds or close curtains during the hours of direct sun, before the heat builds up indoors.
- Use the timer instead of leaving the unit running all day unmonitored.
- Don't place furniture or objects in front of the indoor unit that block the airflow.
- Make sure the outdoor unit has clear space around it to dissipate heat properly — a blocked unit performs worse and uses more electricity.
- Close doors to rooms you're not cooling, so you're not conditioning extra square metres for nothing.
Is it worth replacing an old unit with an inverter one?
If your unit is more than 10-12 years old, it's probably on/off and on a far lower energy class than today's units. With heavy use (a second home occupied several months a year, or a main residence used daily through summer) the consumption gap between that unit and a modern inverter one is usually enough for the savings on your bill to pay back the investment within a few years, on top of gaining quieter operation and steadier temperatures. We can confirm it with real numbers for your specific case during the free technical visit.