Fans, air conditioning, heaters and dehumidifiers for a Spanish flat

Terms used

• Moho — Moho is the mould that grows on walls and ceilings in damp, poorly ventilated homes.
• Comunidad de propietarios — The comunidad de propietarios is the owners' association of a building, which decides on shared parts such as the facade.
• Estatutos — The estatutos are a building's written community rules, which may ban or limit things like facade air conditioning units.
• Potencia contratada — The potencia contratada is the maximum electrical power, in kW, your supply contract allows at one time.
• ICP — The ICP is the power control switch that cuts supply when you use more than your contracted power.

Key rules

• Outdoor AC unit: Get community approval, or your landlord's written consent if you rent, before any outdoor unit goes up.
• Butane and catalytic stoves: Use them only with permanent ventilation, never while sleeping, and fit a CO detector.
• Damp: Use a dehumidifier for mould; desiccant models suit cold rooms and compressor models suit warm ones.
• Power cuts: Heaters plus the oven can pass a 4.6 kW contract, so stagger use or ask to raise your contracted power.
• Cheapest heating: An inverter split air conditioner used as a heat pump costs much less to run than plug-in electric heaters.

Start with the problem you have

• Hot summers: a fan first, then a split air conditioner if you need real cooling.
• Cold winters, no central heating: an electric heater with a thermostat, or a split unit that also heats.
• Damp and mould (moho): a dehumidifier, not a heater.

Whatever you choose, check your contracted power and your permissions first. Both are covered below.

Cooling

Fans are the cheapest option, at tens of euros. They use little power but only move air, so they do not lower the temperature.

Portable air conditioners cost from a few hundred euros. They are noisy and less efficient, and they need a hose out of a window for the hot air.

Split air conditioners have an indoor unit and an outdoor unit. Inverter models are the most efficient and quiet, and they can also heat. They cost from several hundred to a couple of thousand euros including installation. A certified installer must fit them.

Evaporative coolers work poorly in humid coastal areas, so skip them there. Prices change, so compare current ones at retailers.

Permission for an outdoor unit

An outdoor unit on the facade, in a courtyard or on a shared roof changes common parts of the building. You normally need approval from the community of owners (comunidad de propietarios). Many community rules (estatutos) ban or regulate facade units. Without such rules, a board vote is usually sought, and you must not harm the building's look, structure or neighbours. A private terrace may be easier, but the rules still apply.

If you rent, you need your landlord's written consent. Without it, you cannot alter the property.

Your town may also have rules on noise, drainage and visibility from the street. Some towns require a notification or a minor works licence. Ask your town hall before you book an installer.

Heating

Common portable options are oil-filled radiators, ceramic fan heaters, radiant or quartz heaters, and low-consumption electric radiators with thermostats.

• A 1.5 to 2 kW electric heater uses roughly that many kWh for each hour it runs. Multiply its kW by your tariff per kWh to get the hourly cost. Check your own tariff, because price varies by time of day.
• Oil radiators and thermostat units switch off and on, so they use less.
• A split air conditioner used as a heat pump is much cheaper to run than any plug-in electric heater.

Butane and catalytic stoves

These stoves are legal and widely used. They are also the riskiest choice, because they give off carbon monoxide (CO) and use up indoor oxygen.

• Use them only in a room with permanent ventilation, and only for a few hours at a time.
• Never sleep with one on. Never use one in a small closed room or a bathroom.
• Buy a model with oxygen-depletion and tilt shut-off. Check the hose and regulator date, and use only the correct butane cylinder.
• Fit a CO detector.
• Never bring a barbecue, brazier or outdoor heater indoors.

Headache, dizziness or nausea are warning signs. Ventilate, leave the room and call 112.

Catalytic stoves also add a lot of humidity, which makes condensation and mould worse. Follow the maker's manual and your gas supplier's instructions.

Dehumidifiers

Older, ground-floor, north-facing, coastal or poorly insulated flats often get winter condensation and mould. A dehumidifier helps. Choose by type:

• Compressor: best in warm rooms. Typically 130 to 300 euros.
• Desiccant: better in cold rooms, so often the pick for a cold, damp flat. Typically 200 to 400 euros.
• Peltier: small models for tiny spaces. Typically 40 to 80 euros.
• Disposable absorbers: for wardrobes. Typically 10 to 15 euros.

These 2025 prices vary by shop and season. Running costs are modest but show up on your bill.

Why the power cuts out

Your home has a contracted power (potencia contratada). When you exceed it, the power control switch (ICP) or smart meter cuts the supply. Typical contracts are 3.45, 4.6, 5.75 or 6.9 kW, and many older flats have about 3.3 kW.

Typical draws:

• Small heater or electric radiator: 1,000 to 2,000 W
• Oil-filled radiator: 1,500 to 2,500 W
• Split air conditioner: 700 to 1,500 W while running, more at start-up
• Oven: 2,000 to 3,500 W
• Induction hob: 3,000 to 7,000 W
• Washing machine or kettle: 2,000 W each

Several heaters plus the oven can easily pass 4.6 kW. To fix it, run appliances at different times, or ask your supplier or distributor to raise your contracted power. A higher power changes the fixed power charge on your bill, and may need an updated electrical certificate and an administrative fee. After a trip, reset the switch in the meter box.

Common questions are answered in the FAQ below.

Frequently asked questions

Can I put an air conditioner outdoor unit on my flat's facade?

Usually not without approval: the outdoor unit sits on a shared part of the building, so you normally need your community of owners to agree, and many community rules ban or limit facade units. If you rent, you also need the landlord's written consent. Your town hall may have noise, drainage or street-visibility rules, so ask whether a notification or minor works licence is needed.

Why does the power keep cutting out when I run heaters and the oven together?

Your home has a contracted power limit (potencia contratada), and the switch at the meter cuts supply when you go over it. Typical contracts are 3.45 kW, 4.6 kW, 5.75 kW and 6.9 kW, and an oven plus several heaters can easily pass 4.6 kW. Stagger your use, or ask your supplier to raise the power, which changes the fixed charge on your bill.

Is it safe to use a butane or catalytic stove indoors?

Yes, they are legal and widely used, but only in a room with permanent ventilation and never while you sleep. Use them for a few hours at a time, never in a small closed room or bathroom, and fit a carbon monoxide detector. If you feel a headache, dizziness or nausea, ventilate, leave and call 112.

Which type of dehumidifier suits a cold, damp flat?

A desiccant dehumidifier suits cold rooms best, while a compressor model works best in warm rooms. Typical prices are 130-300 euros for compressor units and 200-400 euros for desiccant ones. For a wardrobe, cheap disposable absorbers at 10-15 euros are enough.