Set the A/C to 26°C, not 22°C: every degree below 26 adds about 8% to consumption, and at 22°C you burn over 30% more for a comfort difference you'll barely notice if a fan is running.

And the move almost nobody makes: cool the house while electricity is cheap — at solar midday (13:00–16:00) or pre-dawn — so you arrive at the expensive evening already cool, without blasting the A/C at 20:00.

The quick plan for a hot day

  1. Thermostat at 26°C. Don't crank it to 18°C "to cool faster" — A/C doesn't cool faster at a lower setting, it just runs longer and overshoots.
  2. Pre-cool in the cheap window. If tomorrow's midday is at 0.065 €/kWh, drop the house a couple of degrees around 14:00. By 20:00 you're starting from cool.
  3. Block the heat outside the house with awnings and blinds before the sun hits the glass.
  4. Run a ceiling fan — it adds roughly 3°C of cooling perception for a fraction of what the A/C draws.
  5. At night, open up. When the street drops below 22°C, ventilate and give the A/C a rest.

PVPC is the Precio Voluntario para el Pequeño Consumidor — Spain's government-regulated tariff. It changes every hour and publishes for the next day around 20:15. If you're on a free-market tariff the prices differ, but the cheap-vs-expensive pattern is the same.

Why the hour matters (and how much)

Air conditioning draws about 1.0 kWh per hour of running. On PVPC, that same hour costs wildly different amounts depending on when you switch it on:

  • At 16:00 (solar midday, ~0.065 €/kWh) → 0.07 € an hour.
  • At 20:00 (evening peak, ~0.210 €/kWh) → 0.21 € an hour.

Same cold air, triple the price. The evening (19:00–22:00) is the most expensive window of the day because all of Spain is cooking, watching TV and running A/C at once — it can triple the daily minimum.

The point isn't to sweat through 20:00. It's to bring the cooling forward into the cheap hours so the unit works less during the expensive one.

The two cheap windows in summer

In summer you get two good moments to lean on the plug:

  • Midday (13:00 – 16:00) — solar generation floods the grid and pushes prices down. It's when the heat is fiercest and when power is cheapest. Use it: pre-cool here.
  • Pre-dawn (02:00 – 06:00) — the cheapest window almost all year. Ideal for the water heater and washing machine, and for flushing the house with cool night air.

Ceiling fan: the A/C's best friend

A ceiling fan doesn't cool the air, but it moves yours — and that fools the body. It adds roughly +3°C of cooling perception while drawing about 1/30th of what the air conditioner uses.

In practice: with a fan running you're as comfortable at 26°C as you'd be at 23°C without one. And the gap between 26°C and 23°C is around 24% of A/C consumption. Almost free comfort.

Block the heat outside, not inside

External shade always beats internal shade. Stop the sun before it touches the glass and the heat never enters; stop it with an inside curtain and the heat is already in the room.

  • Toldos (awnings) and persianas (roller blinds) are external shade — the Spanish standard for a reason.
  • A south-facing window in full sun can gain 4–6°C indoors. Block it and you can run the A/C at 26°C instead of 24°C.
  • Lower the blinds during the hours the sun hits that specific window directly.

The night-air trick

Across most of Spain, summer nights drop below 22°C, even in July. Use it:

  • Open windows around 23:00 and let the cool street air in.
  • Close up with the blinds down around 09:00, before the heat returns.

You trap the cool night air inside and start the day without switching anything on. Four to five months a year of free cooling.

And if you want the exact cheapest hour…

PVPC changes hourly and publishes around 20:15 for the next day. The homepage shows the 24-hour heatmap with the cheapest hour marked green — for today and tomorrow. Watch where the midday price drops and pre-cool there.

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