The problem: Guest-driven AC waste is treated as a summer problem, priced on a cooling season of roughly 150 days. In continental Spain that framing misses half the bill: the same reverse-cycle split unit that cools a Madrid room in July heats it in January, and guests misuse it in both modes.
What we did: We modelled the annual recoverable waste of a reverse-cycle mini-split under continental operating conditions, using the locked constants behind the narveo.eu savings calculator: a 1.2 kW average split unit, 35% recoverable waste, €0.25/kWh and 14–15 hours a day of blended runtime.
What we found: Unit size is not the lever; climate and season length are. A continental property has two waste seasons where a coastal property has one, which is why year-round properties sit in the upper half of the published €190–450 per-unit band, modelled at roughly €300–400 per AC unit per year, about double a comparable coastal, cooling-only operation.
What it means in euros: A 9-room Madrid hotel with nine AC units models at roughly €2,800 a year (€2,500–3,300 across 13–17 hours a day of runtime). A continental hotel with 50 rooms and 50 AC units, using the published band, recovers €9,500–22,500 a year, weighted towards the top of that range.
This paper models the annual guest-driven energy waste of reverse-cycle mini-split air conditioning systems in continental Spanish climates, where the same unit provides cooling in summer and heating in winter. It quantifies why season structure, not unit size, is the dominant variable in per-unit savings from enforced temperature and runtime limits.
Coastal, cooling-only properties operate one waste season of roughly 150 days. Continental properties operate two, covering most of the year. Applying the locked modelling constants of the narveo.eu savings calculator (1.2 kW average electrical draw, 35% recoverable waste, €0.25/kWh, 14–15 hours per day of blended runtime), continental properties model at roughly €300–400 recoverable per AC unit per year, in the upper half of the published cross-segment band of €190–450, and roughly double comparable coastal operations.
All figures are modelled planning references, not measured guarantees, and vary with occupancy, season length, building envelope and tariff.
Is an AC limiter a summer product? On the Spanish coast, largely yes: the cooling season runs roughly 150 days and the unit sleeps for the rest of the year. In Madrid the answer changes, because the unit never sleeps. The same reverse-cycle split heats the room from November to March, guests misuse heating exactly the way they misuse cooling, and a limit that works in both modes earns money in both seasons.
Most wall-mounted mini-splits installed in Spanish rentals and hotels are reverse-cycle heat pumps. In summer they move heat out of the room; in winter the cycle reverses and they move heat in. In coastal and island markets such as Ibiza, winters are mild enough that the heating mode sees light use, so the economics of guest misuse are dominated by a single cooling season. Continental Spain is a different climate. Madrid summers reach the mid-thirties and its winters regularly sit near or below 5°C overnight, so the same unit that runs 14 hours a day in July runs comparable hours in January, in the opposite direction.
This is the structural fact the summer framing misses. A property in Madrid, Zaragoza, Seville's inland belt or Castilla-La Mancha does not have a 150-day exposure to guest-driven waste. It has an exposure covering most of the year, interrupted only by the mild shoulder weeks of spring and autumn.
The behaviour documented in cooling has an exact winter analogue. In summer, a guest walks into a warm room and presses the setpoint to 16°C, the mechanical minimum, because lower feels faster. In winter, a guest walks into a cool room and presses it to 30°C, the mechanical maximum, for the same reason. In both cases the misconception is identical (extreme setpoints do not condition the room faster), the incentive is identical (the guest pays nothing per kWh) and the runtime pattern is identical (the unit left running in an empty room while the guest is out).
The reference bands are symmetrical too. The EU comfort standard EN 16798-1 puts mechanically conditioned summer comfort at roughly 23–26°C and winter comfort at roughly 20–24°C. Spain's energy-austerity decree RD 14/2022 drew its lines at 27°C for cooling and 19°C for heating in public and commercial buildings, deliberately outside the comfort bands in both directions. A guest at 16°C in July and a guest at 30°C in January are the same event on opposite ends of the dial: a setpoint far past comfort, paid for by someone else.
A temperature band limit therefore works twice. Narveo's limit is a band, not a floor: it caps how cold a guest can set the room in summer and how hot in winter, and its auto-shutoff ends unattended runtime in both modes. Nothing about the mechanism is cooling-specific.
All euro figures in this paper derive from the same locked constants used by the narveo.eu savings calculator, so a reader can reproduce every number:
| Constant | Value | Note |
|---|---|---|
| Average split unit electrical draw | 1.2 kW | Electrical input, not cooling capacity |
| Recoverable waste share | 35% | Share of runtime energy removed by band + runtime limits |
| Electricity tariff | €0.25/kWh | Base of the real EU range of €0.22–0.29 |
| Blended runtime | 14–15 h/day | Mix of guests who switch off and the majority who do not |
| CO₂ factor | 0.24 kg/kWh | ≈ 0.96 kg CO₂ per €1 saved |
| Season structure | ~150 days coastal · year-round continental | The variable this paper isolates |
Run the arithmetic and the mechanism is visible in one line: 1.2 kW × 14–15 hours × 35% × €0.25 yields roughly €1.50 of recoverable waste per unit per occupied high-season day. What separates property types is how many such days the year contains. A coastal, cooling-only property accumulates them across one season. A continental property accumulates them across two.
Unit size is not the lever. A Madrid hotel room and an Ibiza villa bedroom run essentially the same 1.2 kW split hardware. What differs is exposure: the continental unit works two seasons, so its annual recoverable waste models at roughly €300–400 per AC unit per year at 14–15 hours a day of blended runtime, in the upper half of the published €190–450 band and roughly double a comparable coastal, cooling-only operation. Properties with the heaviest, longest-season use model higher still.
Take an independently run 9-room hotel in central Madrid: nine rooms, nine AC units, open year-round. At the modelled continental figure of roughly €310 per AC unit per year, the property's annual recoverable waste is approximately €2,800, with a range of €2,500–3,300 across 13–17 hours a day of runtime. That is the revenue of about three fully booked nights, recovered every year without a single room out of service. It also amounts to roughly 2.7 tonnes less CO₂ per year, a figure worth noting for operators with sustainability reporting obligations, though the euros are the case.
Scale the same logic with the published band and the portfolio maths follows: a continental hotel with 50 rooms and 50 AC units recovers €9,500–22,500 a year, weighted towards the top of the range; an agency managing 30 continental villas at roughly 5 AC units each, about 150 AC units, is looking at €28,500–67,500 across the portfolio.
At €69 per unit retail, the published payback of one season, typically 30 to 75 days and around one month at fleet scale, is calibrated on a single cooling season. A continental property does not wait for next summer to finish paying back: a unit installed in October earns through the heating season immediately. Two seasons do not shorten the headline payback claim, which stays at one season, but they remove the dead months from the cash-flow picture. There is no time of year when a continental installation is idle capital.
Narveo in one sentence: Narveo is a plug-and-play AC controller for rental properties and hotels that limits the temperature band and auto-shuts off after a set time, in heating and cooling alike – no WiFi, no app, no professional installation, €69 per unit, made by Xeno Solis, S.L. in Spain.
Every euro figure in this paper is modelled, not metered. The model assumes the locked calculator constants (1.2 kW, 35% recoverable waste, €0.25/kWh, 14–15 h/day blended runtime) and real properties will deviate with occupancy, building envelope, unit age, tariff contract and guest profile. Figures should be read as central planning estimates, not guaranteed outcomes; for a specific property, the narveo.eu savings calculator with that property's own occupancy and season inputs is the right tool.
The continental segment figure of roughly €300–400 per unit per year assumes a genuine dual-season market such as Madrid: hot summers and winters cold enough for daily heating use. Markets with mild winters (the Balearic and Canary coasts, much of the Mediterranean littoral) should use the lower half of the published €190–450 band. The published band is the cross-segment figure; the segment split explains its width rather than replacing it.
The analysis covers reverse-cycle wall-mounted mini-splits under individual room control. Properties heated by gas boilers, radiators or underfloor systems gain nothing in winter from an AC controller, and centralised or BMS-managed HVAC sits outside Narveo's compatibility entirely. Properties where usage is already tightly managed, or where guests pay metered electricity, have less waste for any control to recover.
Winter heating waste is modelled as symmetrical to summer cooling waste in runtime and setpoint behaviour. This is a reasonable structural assumption supported by the identical incentive position of the guest, but heating-specific field measurements in Spanish rental stock are thinner than the cooling evidence base, and the winter half of the model carries correspondingly wider uncertainty.
Narveo caps the temperature band and auto-shuts off after a set time, in heating and cooling alike. No app. No WiFi. No installation. Pilot Narveo in 25% of your rooms, minimum 5 units, and recover €190–450 per AC unit this year.
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