Heating & cooling · Guide
Heating a Portuguese house in winter: what works, what it costs and how to beat the damp
Many newcomers are shocked by how cold a Portuguese house can feel indoors in January. The problem is usually insulation and damp, not the outdoor temperature. Here's how to stay warm without a painful bill.
This guide contains affiliate links. If you buy through them we may earn a small commission, at no extra cost to you. It never changes what we recommend. How we make money.
Key takeaways
- Air-to-air heat pumps (reversible AC) deliver typically 3–4 kWh of heat per kWh of electricity — far cheaper than oil-filled or fan heaters.
- Damp makes rooms feel colder and causes mould: ventilate briefly every day and keep humidity around 40–60%.
- Heat the rooms you use, when you use them; close doors and curtains at dusk.
- Smart thermostats and humidity sensors pay off quickly in large, poorly insulated houses.
Why Portuguese houses feel so cold
- Many older homes have solid walls, single glazing and little or no roof insulation.
- Central heating is the exception, not the rule — houses were built to stay cool in summer.
- Humid winter air plus cold walls leads to condensation and mould, and damp air feels colder at the same temperature.
Comparing heating options
The fairest comparison is the cost of one kWh of useful heat. With electricity at roughly €0.20/kWh including VAT, a heat pump with an efficiency (COP) of 3–4 produces heat for about €0.05–0.07 per kWh, while any resistive electric heater costs the full €0.20.
| Heater | Efficiency | ≈ Cost per kWh of heat | Notes |
|---|---|---|---|
| Air-to-air heat pump (reversible AC) | COP 3–4 | €0.05–0.07 | Also cools in summer; efficiency drops in very cold weather |
| Oil-filled radiator / fan heater / convector | 100% | €0.20 | Cheap to buy, expensive to run |
| Bottled gas heater (butano) | — | varies with bottle price | Adds moisture to the air — worse for damp |
| Wood burner / salamandra | — | low if you have wood | Great in rural homes; needs a safe flue and dry wood |
| Pellet stove | — | moderate | Automatic, clean; needs electricity and pellet storage |
Tackle damp first
- Ventilate 5–10 minutes a day with windows wide open (not tilted all day).
- Use extractor fans in kitchen and bathroom; dry laundry outside or in a tumble dryer, not on radiators.
- Measure: cheap temperature & humidity sensors in each room show where the problem is.
- If humidity stays above ~65% in a room, a dehumidifier protects walls and furniture — and makes the room feel warmer.
- Avoid unflued gas heaters indoors: they add a lot of water vapour.
Cheap upgrades with big effect
- Heavy curtains and closing shutters (estores) at dusk.
- Draught strips on doors and windows; a draught excluder under external doors.
- Rugs on tiled floors.
- Roof/loft insulation — usually the best structural upgrade per euro.
- Window upgrades and wall insulation are bigger projects; check the Fundo Ambiental site for any open support scheme before you start.
Smart control
Most modern split ACs can be controlled via Wi-Fi or an IR blaster. Combined with room sensors, Home Assistant can pre-heat a room before you get up, switch off when windows open, and warn you when humidity climbs. See our Home Assistant energy guide.
Frequently asked questions
What is the cheapest way to heat a house in Portugal?
For most homes with electricity only, a heat-pump air conditioner is the cheapest per unit of heat. In rural homes with a free or cheap wood supply, a good wood burner can beat it.
Why is my house colder inside than outside?
Thick, uninsulated stone or brick walls stay cold and release that cold slowly, especially on the shady side. Heating the air helps less than reducing draughts and damp.
Should I run the AC all day?
In a poorly insulated house it's usually cheaper to heat the rooms you're using, when you use them, and keep doors closed.
Sources
- Preço do kWh por fornecedor em 2026 — Literacia Financeira (accessed 29 October 2026)
- Fundo Ambiental: apoios para tornar a casa mais sustentável — Santander Portugal (accessed 29 October 2026)