How much does a portable air conditioner consume in Lisbon?

The short answer: between €1.80 and €3.20 per day of normal use (8 hours) in Lisbon, with the 2026 EDP simple tariff. The long answer explains why it varies, and why you'll always pay more than the label says.

The base numbers

• EDP simple tariff 2026: ~€0.1839/kWh (contracted power 6.9 kVA)
• Two-rate tariff (off-peak): ~€0.1051/kWh (10pm to 8am)
• Typical 9000 BTU portable AC: 0.9–1.2 kWh consumed per hour while running
• 12000 BTU portable AC (larger): 1.2–1.5 kWh/h

Calculation: a typical Lisbon scenario

Case 1: Sleeping with the AC (a 3-bed flat in Alfama)

A 9000 BTU AC in the bedroom, from 11pm to 7am (8 hours, off-peak tariff).

• 1.0 kWh × 8 h × €0.1051/kWh = €0.84 per night
• The whole month of August (30 nights) = ~€25/month

Case 2: Working from home (a 2-bed flat in Príncipe Real)

The AC in the living room/office from 10am to 6pm (8 hours, simple or daytime tariff).

• 1.1 kWh × 8 h × €0.1839/kWh = €1.62 per day
• The whole month = ~€48/month

Case 3: Intensive use (a tourist flat in Bairro Alto)

AC running 14h/day, two spaces, a 12000 BTU model.

• 1.3 kWh × 14 h × an average of €0.15/kWh = €2.73 per day
• The whole month = ~€82/month

Quick table: cost per hour in Lisbon

Why real consumption is always higher than the label

1. Compressor cycle. The label shows consumption at 100%. In practice, the unit switches on/off to maintain the temperature. Real efficiency: ~85% of nominal.
2. Heat entering through the hose. The exhaust hose also heats up and returns heat to the room. Seal it well with the window kit.
3. Old Lisbon flats. Thin walls, single glazing, no insulation. The AC works harder to compensate.
4. Adjusting the temperature. Each degree below 24 °C raises consumption by ~7%. Keep it at 24–25 °C, not at 20 °C.

How to reduce consumption (5 tricks)

1. Set it to 25 °C, not 18 °C. You won't notice the difference as much, but the meter will.
2. Use the "night" / "sleep" function. The AC automatically rises 1 °C every 2 hours. You sleep well and save 30%.
3. A two-rate tariff if you use it a lot at night. It's worth it if you concentrate more than 60% of consumption between 10pm and 8am. Check your EDP plan.
4. Seal the hose at the window. Use the kit that comes with the unit or improvise with cardboard and tape. Without sealing, you lose 30% of the capacity.
5. Switch it off 20 minutes before leaving. The room stays cool through inertia.

Comparison: AC vs fan vs evaporative cooler

A standing fan consumes 25× less than an AC. For 24 °C nights in cooler areas (Belém, Parque das Nações), it may be enough.

An evaporative cooler ("air cooler") consumes 10× less, but it only works in dry environments. In Lisbon with high humidity, it's practically useless — it dampens the air instead of cooling it.

Air conditioning is the only solution that really cools in high humidity. The cost is higher, but the result is incomparable.

Summary

For normal use in Lisbon, plan for €30–60 extra on your electricity bill per active summer month. Add the rental (a monthly plan from €450/month) and you're still below the cost of buying + installing a split, with the advantage of not having equipment sitting idle in winter.