The bottom line — Many expats arriving in the Algarve think heating is unnecessary here. Wrong — Portuguese winters are more humid and colder indoors than the outdoor climate (8-15°C) suggests. The good news: your reversible inverter AC is enough in 90% of cases, and it’s 3-4× cheaper than electric radiators. Here are the real needs, actual performance, and when to plan a backup.

Algarve winter: myth and reality

The expat myth

“The Algarve is southern Europe, you don’t get cold in winter.”

The reality

December to February: 8-15°C average outside, 5-10°C at night
Portuguese homes: often poorly insulated (single glazing, thin walls, uninsulated ceilings)
No systematic central heating
70-85% humidity = amplified cold sensation
Indoors without heating: 14-18°C in mid-winter

➡️ Bottom line: heating is essential 3-4 months a year for comfort, especially for elderly or children.

Reversible inverter AC in heating mode

How it works

A reversible AC operates on the air-to-air heat pump principle: – Captures calories from outside air (even at 5°C) – Transfers them to indoor air – Returns 3-4 kWh of heat per 1 kWh consumed

Key Algarve numbers

Winter COP (Coefficient of Performance):
At +10°C outside: 4.0-4.5
At +5°C outside: 3.5-4.0
At 0°C outside: 2.8-3.2
At -5°C outside: 2.2-2.5 (limit)

➡️ In the Algarve, where temperatures rarely drop below 5°C, AC remains very efficient (COP 3.5-4.5).

Heating comparison in the Algarve

To heat 6 months (Oct-Mar) a 3-bed 80 m² home with 4,000 kWh thermal need:

System	Electrical use	Annual cost	Installation cost
Reversible inverter AC	~1,100 kWh (COP 3.6)	€240	already installed for summer AC
Air-to-water heat pump	~1,000 kWh (COP 4.0)	€220	🥇 high-end
Electric radiator	4,000 kWh (COP 1.0)	€880	🥉 very low
Gas heater	equivalent ~3,000 kWh	€700 (gas)	🥈 mid
Oil central heating	equivalent	€950	🥇 very high
Wood-burning stove	n/a	€350 (cords)	🥈 mid

The verdict

Reversible AC is 3-4× cheaper than electric radiators for the same comfort. And you have no extra installation to plan if you already have AC for summer.

Cases where AC is more than enough

✅ Profile A — Well-insulated 80-150 m² home

Thick stone walls or insulated breeze block
Double glazing
Insulated ceiling
3-4 unit multi-split
Conclusion: AC covers all winter needs

✅ Profile B — City flat (Faro, Tavira)

Shared walls (neighbours’ heat)
Usually well-oriented
2-3 unit multi-split
Conclusion: AC more than enough

✅ Profile C — Modern new villa

Recent build with thermal regulations
High-end multi-split or ducted
Conclusion: AC over-performs, even at 50% use

Cases where AC alone struggles

⚠️ Profile A — Old poorly-insulated home

Single glazing, thin walls
Uninsulated ceiling or flat roof
Area > 200 m²
Conclusion: AC will struggle to comfortably hit 22°C on the coldest days
Solution: AC + wood-burning stove pairing or occasional backup

⚠️ Profile B — Whole upper floor without AC

Multi-split covers ground floor but not upper
Upper floor 12-15°C on winter mornings
Conclusion: add upper-floor units or backup radiators

⚠️ Profile C — Cold-sensitive elderly people

Need constant 23-25°C minimum
AC may struggle in cold peaks
Conclusion: plan for backup (air-to-water HP or low-consumption radiators)

Tips to optimise AC heating

🔧 1. Size it right

An undersized AC will run 24/7 without reaching setpoint. Follow the BTU table with +15-20% winter uplift (setpoint/outdoor gap is bigger than in summer).

🔧 2. “Heat” mode + auto ventilation

No need to set 28°C. 20-22°C is optimal comfort. “Heat Auto” mode adjusts ventilation by itself.

🔧 3. Heat all day at low intensity

More efficient than going from 14 to 22°C morning and evening. Schedule 18°C at night, 22°C during the day.

🔧 4. Air the home in the morning

Just 10 minutes to flush humidity (which amplifies cold sensation). Then close up.

🔧 5. Take advantage of solar

With PV panels: AC heating runs mainly when there’s sun (10am-4pm). Natural synergy, 60-70% self-consumption in winter.

🔧 6. Seal air leaks

Window and door seals: €5-10 spend, 30-40% saving on heating bill.

Frequently asked questions

What heating temperature in the Algarve?

Living room daytime: 21-22°C
Bedrooms at night: 17-19°C (sleep)
Bathroom: 23-24°C briefly (shower)

Does AC really heat when raining?

Yes — AC works by thermal energy capture, not solar. Rain doesn’t affect. Strong wind can slightly disturb (-5% efficiency).

Is heat mode noisier?

Slightly more than cool mode, as the compressor works harder. Choose silent/Quiet mode at night.

Do my filters get dirty faster in winter?

Yes — AC moves more air to heat. Clean every 2 months instead of 3.

Can a reversible AC replace existing central heating?

Yes in 80% of Algarve cases. Cut central heating for one test season to validate.

Frost sometimes appears on the outdoor unit in winter — is that normal?

Yes — automatic defrost mode activated. For 5-10 min, AC stops heating (reversed cycle). Normal.

Should I invest in a separate air-to-water HP?

Not in the Algarve unless: – Home > 200 m² very poorly insulated – Underfloor heating already in place – Need centralised hot water See our HP vs AC comparison.

Does AC use more in heat or cool mode?

In heat slightly more (lower COP), but shorter usage period (briefer season). Overall equivalent or less than cool mode over the year.

Our recommendation by case

Profile	Our advice
1-2 bed flat well insulated	1 inverter split suffices
3-bed standard home	3-unit multi-split = full heating
4-5 bed old poorly insulated	Multi-split + wood stove or backup
New 5-bed+ villa	Ducted or air-to-water HP + underfloor heating
Coastal humid home	Multi-split + regular dehumidify mode

❄️🔥 Request a CLIMEDGE heating audit — winter needs analysis, suitable sizing.

Read further

📄 How to choose air conditioning in the Algarve
📄 Inverter vs non-inverter AC
📄 Heat pump vs reversible AC: which solution for the Algarve
📄 How many BTU for my room?
📄 Powering your AC with solar in the Algarve

About the author — Grégory FRANCHI runs CLIMEDGE, a company specialising in residential solar PV and air conditioning across the Algarve.

📧 info@climedge.pt — 🌐 climedge.pt