Types of air conditioning: which one makes the most sense?
1) Split (fixed) — the “balanced” choice
Advantages: more efficient, quieter, and better long-term comfort. DECO highlights that fixed systems tend to be quieter and more efficient than portable ones.
Warning: Installation required.
2) Multi-split — multiple rooms, one outdoor unit
A good option if you want to air-condition 2-4 rooms while keeping the facade cleaner.
3) Portable — a quick solution (with compromises)
It's tempting because it's cheaper and doesn't require construction work, but DECO (a Portuguese consumer protection organization) emphasizes that it's not comparable to a split system in terms of efficiency and needs an exhaust pipe in a window (ideally with an adapter to reduce losses).
4) Duct/cassette systems (more "construction-related", more integrated)
It generally makes sense for renovations or larger projects.
Step 1: Correct power (BTU/kW) — the biggest mistake is "buying by sight"
Power requirements should take into account area , sun exposure , windows , insulation , and occupancy . DECO provides practical guidelines:
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18–20 m² → ~9000 BTU/h (≈2.5 kW)
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20–35 m² → ~12000–13500 BTU/h (≈3.5–4 kW)
And in large rooms with lots of light and windows, it may be necessary to go up quite a bit.
Useful tip in Portugal: EDP also uses the "standard" of 9000 BTU for small rooms (e.g., bedroom) in our climate and typical construction.
Step 2: Energy Efficiency (SEER/SCOP) — where the money is made.
When comparing models, don't just look at BTU. The energy label in the EU considers seasonal metrics:
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SEER (cooling efficiency)
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SCOP (heating efficiency, in reversible appliances/heat pump)
This is in line with the energy labeling of air conditioners in the EU (Regulation 626/2011).
And manufacturers/industry entities explain the logic of "seasonal efficiency" (it's not just the peak season, it's the behavior throughout the season).
Simple rule: for frequent use, it's worth choosing a higher energy class and good SEER/SCOP values.
Step 3: Noise, comfort, and features that really matter
Look for these points in the technical specifications:
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Noise (dB) — especially for bedroom/office (the energy label also includes sound).
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Inverter technology helps maintain a stable temperature and reduce peak consumption (in practice, more comfort).
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Dehumidification — very useful in humid areas.
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Wi-Fi/App + timer — helps you use it "wisely" (fewer unnecessary hours).
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Filters — good for dust and maintaining air quality (not a "miracle," but it helps).
Installation in Portugal: certified technician and best practices
DECO is clear: installation must be carried out by a certified technician , who connects the units, tests their operation and explains their use/maintenance.
To confirm certification and official listings, the APA provides pages/listings of certificates/attestations for HVAC/R technicians.
Practical tips before installing:
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Request 3 quotes (the price varies depending on pre-installation, materials, distance, and complexity).
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Consider the position of the indoor unit (direct airflow onto the bed/sofa is a common mistake).
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If it's portable: use a window adapter whenever possible to reduce losses.
Consumption: How to estimate it quickly (without guessing)
DECO suggests a simple way:
Power (kW) × hours/day = kWh/day , and then you multiply by the price per kWh.
Example (for educational purposes): 1 kW used 5 hours/day → 5 kWh/day.
To save money without sacrificing comfort:
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Sets the temperature to 24–26°C in the summer and avoids "freezing the house" (the increase in consumption is real).
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Close doors/windows and reduce heat entry (blinds/curtains)
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Cleans filters (airflow = efficiency)
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uses timer/echo/routines
Quick checklist (smart shopping)
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✅ Type: split (frequent use) vs portable (occasional use/no installation required)
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✅ Correct BTU for square meters and room conditions
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✅ Good energy class + strong SEER/SCOP
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✅ Low noise level (bedroom/office)
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✅ Installation by a certified technician (Portugal)
FAQ
1) Split system or notebook: which consumes less power?
In general, split systems are more efficient and tend to consume less energy for the same level of comfort; portable units lose efficiency and require exhaust through a pipe in the window.
2) How many square meters does 9000 BTU cover?
DECO lists approximately 18–20 m² as a reference, but factors such as sunlight and windows may require more.
3) Do I really need a certified technician?
Yes — DECO recommends installation by a certified technician , and there are official (APA) listings for consultation.
4) What do SEER and SCOP mean?
These are seasonal cooling efficiency (SEER) and heating efficiency (SCOP) indices used in energy labeling.