How much does your hotel lose on heating empty rooms? The numbers, with real data

HVAC represents between 40% and 60% of total energy consumption in an average hotel in Spain. A significant share of that spend is wasted on rooms with nobody in them.

In this article we run the calculation in detail, with real numbers measured in Controlá installations during 2025, across three different hotel sizes and Spain's most representative climates.

(Figures based on Controlá internal measurements in hotels deployed during 2025 in Barcelona, Granada and the coastal zone. Variability by system type, installation age and guest behaviour.)

The invisible problem

Imagine a 50-room hotel with average 70% occupancy. That means, at any given moment, around 15 rooms are empty. If HVAC keeps running in those rooms, the hotel is paying to cool or heat air no one enjoys.

How much exactly? Depends on system type, climate and idle time. Let's see.

Typical consumption per room

Real measurements in rooms where Controlá has sensors:

System type	Average consumption while running
Traditional split (residential)	1.2 - 2.5 kWh
Modern inverter split	0.8 - 1.8 kWh
Fancoil with central boiler	0.5 - 1.2 kWh (heat) / 1.0 - 2.0 kWh (cool)
Centralised aerothermal	0.4 - 1.0 kWh
Modern VRF/VRV	0.6 - 1.5 kWh

Variability depends heavily on setpoint, the gap with outdoor temperature, and room insulation.

Current electricity cost

At Spain 2025 prices:

• Typical hotel contracted tariff: €0.15 - €0.22/kWh
• We assume an average €0.18/kWh for the calculation.

(Hotels with indexed tariffs or solar self-consumption can have very different costs. These calculations assume a fixed average tariff.)

The calculation: 3 hotel sizes

Let's see how much is lost in a realistic scenario.

Small hotel: 20 rooms, urban, Madrid

• Average annual occupancy: 65%
• Average empty rooms: 7
• Average per-room consumption with HVAC on (Madrid, annual): 1.1 kWh
• Hours/day with HVAC on while empty (conservative estimate): 6 h
• Daily waste: 7 × 1.1 × 6 × 0.18 = €8.3/day
• Annual cost: ≈ €3,000

Mid-sized hotel: 50 rooms, leisure, Málaga

• Average annual occupancy: 72%
• Average empty rooms: 14
• Average per-room consumption (Málaga, AC-dominant): 1.6 kWh
• Hours/day with HVAC on while empty: 8 h
• Daily waste: 14 × 1.6 × 8 × 0.18 = €32.3/day
• Annual cost: ≈ €11,800

Large hotel: 100 rooms, urban, Barcelona

• Average annual occupancy: 75%
• Average empty rooms: 25
• Average per-room consumption (Barcelona, mixed cooling/heating): 1.3 kWh
• Hours/day with HVAC on while empty: 7 h
• Daily waste: 25 × 1.3 × 7 × 0.18 = €40.95/day
• Annual cost: ≈ €14,900

Summary

Hotel size	Estimated annual waste
20 rooms	~€3,000
50 rooms	~€11,800
100 rooms	~€14,900

These numbers assume a conservative scenario. In hotels with higher occupancy or more extreme climates (Seville, Las Palmas, Sierra Nevada in winter), figures can be 30-50% higher.

Why this happens

The problem isn't negligence. Hotels operate with systems that aren't designed to respond to actual occupancy:

1. Thermostats are manual

The guest leaves AC on going for breakfast, the beach, the street. Nobody turns it off until housekeeping enters (hours later) or until the guest returns.

2. No physical occupancy visibility

The reception system (PMS) knows which rooms have active bookings, but doesn't know if the guest is physically inside. A booked room with the guest out all day still shows as "occupied" but is empty.

3. Centralised systems don't distinguish

Centralised HVAC (typical in 4-5 star hotels) cools or heats whole zones at the same times, regardless of zone-by-zone occupancy. An entire floor can be running with just 2 guests inside.

4. Lack of measurement

Without per-zone consumption sensors, the hotel only sees the monthly total on the bill. It doesn't know where energy goes, so it can't act.

The solution: occupancy-based automation

With presence sensors and smart automation, HVAC adjusts automatically:

• When the guest leaves, the system reduces power (doesn't turn off completely, so they return to comfort), but stops "blasting" energy.
• When the guest returns, the temperature restores to the configured setpoint in minutes.
• If the room is empty between guests (between checkout and check-in), the system enters full eco mode.
• If a window is left open, the system turns off automatically and alerts housekeeping.

What tech to use

For this to work without disturbing the guest, you need to choose sensors well:

• PIR (infrared): cheap but doesn't detect static presence (sleeping guest = false empty). NOT recommended alone.
• mmWave: detects continuous presence, even during sleep. Recommended in rooms.
• PIR + mmWave combo: what we use at Controlá usually.

We cover this in detail in our presence sensor guide for hotels.

How much do you actually save

Hotels implementing occupancy-based automation report savings between 20% and 35% of HVAC consumption (Controlá internal data, 2025 measurements).

Applied to the three examples above:

Hotel size	Annual waste	Typical savings (25%)	Estimated system ROI
20 rooms	€3,000	€750 - €1,050	12-18 months
50 rooms	€11,800	€2,950 - €4,130	6-12 months
100 rooms	€14,900	€3,725 - €5,215	6-12 months

ROI improves as the hotel gets larger and the climate more extreme (more base consumption = more absolute savings).

What does implementing this cost?

For a 50-room hotel, a typical Controlá installation with presence sensors + climate control:

• Initial investment: €3,500 - €6,500 (hardware + installation)
• Monthly subscription: depends on volume, typically €4-8 per managed room

Combined payback, considering energy savings + housekeeping improvements (not having to enter so many rooms to turn things off manually), is usually between 8 and 14 months.

What to verify before investing

Before deploying sensors, it's worth running a 2-4 week consumption audit. This means:

1. Install temporary meters on sample rooms
2. Measure real climate consumption under current operations
3. Estimate real savings potential for your specific hotel (not a sector average)
4. Decide with numbers whether the deployment is worth it

At Controlá we do this audit as first step in nearly every project. It avoids investing in something that won't give the expected return in your particular case.

Conclusion

Wasted energy in empty rooms is a silent but significant problem. For a mid-sized hotel, we're talking about €10,000 to €20,000 a year thrown away.

Good news: tech to fix it already exists, is mature, and doesn't require construction or replacing existing HVAC. With well-chosen sensors and a platform that integrates with your PMS, savings are direct and measurable.

Want to know how much YOUR hotel loses?

If you manage a hotel and want concrete numbers on how much you're losing (and how much you could save):

Book a 30-minute call. We'll give a first estimate based on your volume, climate and installation type, no commitment.

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Consumption figures, average occupancy and savings come from Controlá internal logs, measurements taken during 2025 in hotels deployed across Barcelona, Granada and the coastal zone. Electricity prices are typical averages for Spanish hotels in 2025. ROI estimates are indicative and depend on each hotel's specific case.