How many frigorías do I need? A quick guide by square metres

Frigorías, BTU and kW: what each one is

All three units measure the same thing — the appliance’s cooling capacity — but on different scales, which is why they confuse people. The frigoría is the cooling unit traditionally used in Spain; the BTU is the anglophone unit shown on almost every spec sheet; and the kW here means cooling capacity, not power draw.

• 1 kW is roughly 860 frigorías/hour (approximately).
• 1,000 BTU is roughly 252 frigorías (approximately).

So a 12,000 BTU unit has around 3,000 frigorías, about what a 3.5 kW unit delivers. You do not need to memorise the figures: the point is that when a listing says "12,000 BTU / 3.5 kW", you can read it as "about 3,000 frigorías". Treat all these conversions as approximations for orientation, not exact values.

The orientative rule: ~100 frigorías per m²

The classic starting point is simple: about 100 frigorías per square metre. For a 20 m² room that is around 2,000 frigorías (a little under 9,000 BTU). It is a back-of-napkin figure, useful so you do not get lost, but only the beginning: the same floor area can demand quite a bit more or less depending on the room.

Raise the estimate if your room gathers heat factors:

• Lots of sun: south- or west-facing, big windows, or no effective blind.
• High ceilings: above 2.5 m there is more air to cool than the floor area suggests.
• Poor insulation or a top floor: a flat under the roof or with heat-storing walls needs more power.
• Heat sources: a kitchen, plenty of electronics, or several people in the room.

And you can lower it a little if the room is internal, shaded, north-facing and well insulated. When in doubt, round up modestly: a small margin helps on heatwave days, but overshooting by a lot has its own problem, as you will see below.

Quick table by square metres

As an orientative reference, starting from the ~100 frig/m² rule and without extreme sun or insulation factors:

• ~10 m²: about 1,000 frigorías, around 5,000–6,000 BTU.
• ~15 m²: about 1,500 frigorías, around 7,000 BTU.
• ~20 m²: about 2,000 frigorías, around 9,000 BTU.
• ~25 m²: about 2,500 frigorías, around 10,000–12,000 BTU.
• ~30 m²: about 3,000 frigorías, around 12,000 BTU.

If your room has lots of sun, high ceilings or sits under the roof, move up a step in the table. Remember these are starting figures for orientation, not a fixed recipe: two 25 m² living rooms can call for different units depending on aspect and insulation.

Why undersizing (or oversizing) is a problem

Choosing power is not simply "the more the better". Both extremes fail, each in its own way.

Undersizing: the unit never reaches the temperature you set, so it runs flat out continuously. The result: it does not cool the room well, uses more electricity than it should, and the compressor suffers from never resting. It is the most common mistake when someone buys "the cheapest one available".

Oversizing by a lot: an over-large unit cools the air quickly, switches off, and restarts a few minutes later (known as short-cycling). Those constant starts consume power, cause wear and, crucially, dehumidify poorly: because it never runs long enough to dry the air, the room can end up cold but with a clammy, unpleasant feel. On top of that, you pay more for power you never use.

The goal is a unit that runs most of the time at a comfortable rate, with well-spaced starts and stops. That is why it pays to size with your head rather than on impulse — it is one of the costliest portable-AC buying mistakes.

Which model fits your size

Mapped onto the units we track, and always as orientation (adjust for sun, ceiling and insulation):

• Small rooms, ~12–15 m²: 7,000 BTU models like the Cecotec ForceClima 7150 (about 1,800 frigorías).
• Medium bedrooms, ~15–18 m²: 8,000 BTU, like the Midea PortaSplit Cool 8,000 (about 2,000 frigorías, cooling only).
• Rooms of ~18–20 m²: 9,000 BTU, like the Cecotec ForceClima 9150 (about 2,270 frigorías).
• Living rooms of ~22–25 m²: 10,700 BTU, like the De’Longhi Pinguino EX105 (about 2,700 frigorías).
• Large or very sunny rooms, ~25–30 m²: 12,000 BTU, like the Midea PortaSplit 12,000 or the Cecotec ForceClima 12800, both heat pumps (about 3,000 frigorías).

If you are torn between the 12,000 PortaSplit and the Cool 8,000 for your room, we have a comparison of the two models. And if you want a no-works machine, here are the three no-install options.

You know your frigorías — now find it in stock

Once the power is clear, the challenge is finding that model available and well priced, exactly when everyone is after the same thing. The most wanted models sell out in hours and return with no notice.

AireRadar watches Spanish shops for you and verifies every change against the product identifier before sending an alert. When the model with the frigorías you need becomes buyable near you, an email or Telegram message arrives with the direct link.

The season pass costs €4.99 one-time, valid until 30 September 2026, with instant alerts; a free tier with a 20-minute delay also exists. We are independent: we sell no appliances and take no commission from shops. You can see how the alerts work before deciding.