As temperatures soar across Spain and millions of residents switch on their air conditioning units, experts are warning homeowners to check where their systems are installed – or risk hefty fines and legal headaches.

While exterior air conditioning units have long been a familiar feature of Spanish streets, many property owners do not realise that mounting one on a building facade can breach both community rules and local planning regulations.

In some cases, residents have been ordered to remove units years after they were installed.

The issue stems from the fact that apartment facades are generally considered a shared element of the building rather than private property.

That means homeowners cannot simply drill into an exterior wall and install an air conditioning unit without considering the rules governing the building.

If neighbours object, they may be able to force the owner to remove the installation through the courts.

And even if nobody complains, local councils can still step in.

Town halls across Spain have become increasingly strict about visible air conditioning units, particularly in historic centres where authorities are keen to preserve the appearance of streets and buildings.

A unit hanging from a balcony or protruding from a facade may be viewed as an unauthorised alteration to the urban landscape.

The penalties can be painful.

Depending on the municipality and the seriousness of the breach, fines can range from a few hundred euros to as much as €3,000.

In addition, homeowners may be required to pay for the unit’s removal and restore the facade to its original condition.

Noise is another common source of complaints.

Air conditioning compressors that disturb neighbours – especially during hot summer nights – can attract attention from local authorities if they exceed permitted noise levels.

Condensation water is also a frequent problem. In many municipalities it is illegal for water from an air conditioning system to drip directly onto public streets below.

For residents living in protected or historic buildings, the rules are often even tougher.

Many old town centres have strict regulations governing anything visible from the street, from satellite dishes and awnings to air conditioning units.

As a result, installations that might be acceptable elsewhere can be prohibited entirely.

Experts recommend checking both community statutes and local planning regulations before installing a system.

With Spain becoming increasingly reliant on air conditioning during longer and hotter summers, authorities are paying closer attention to where units are placed.

What seems like a straightforward installation today could end up becoming a costly problem tomorrow.