The problem: guests in holiday rentals don't pay the electricity bill, so the AC runs all night. In a typical Ibiza rental bedroom with a 1.2 kW unit, that means up to 8–9 kWh consumed in a single day — hours of runtime on top of what any reasonable night's sleep would require.
What we did: installed dedicated power monitors on the AC circuits in three comparable bedrooms — same size, same orientation, same unit capacity — and measured consumption with and without Voltvert active. Weather data was logged on the same days to rule out cooler temperatures as a confounding factor.
What we found: peak daily consumption dropped from 6.90 kWh without Voltvert to 2.50 kWh with it active — a 64% reduction recorded on comparable-temperature days in the same rooms. On Voltvert days, consumption ranged between 2.50 and 3.79 kWh. The AC still ran. The room was still comfortable. The waste was just gone.
What it means in euros: a typical 5-bedroom villa saves over €600 in a single summer season. The devices pay for themselves before the season is halfway through.
Saying a product saves energy is easy. Proving it is harder. This article documents what actually happened when we installed power monitors on AC units in three rental bedrooms and switched Voltvert on and off.
Why we did this test
Voltvert's savings claims are built on a straightforward model: AC units in holiday rentals frequently run longer than necessary because guests have no incentive to manage them carefully. By capping runtime and enforcing a sensible setpoint, the unit still cools the room — it just stops when it has done its job rather than running through the night.
That logic is sound, but property managers and hotel operators are right to ask for numbers. So instead of asking them to trust a model, we created one ourselves: a controlled test using dedicated power monitors in real rental bedrooms.
The test setup
Using a dedicated power monitor on each AC circuit meant the readings reflected only the air conditioner — no other appliances, no household baseline. This is important: in most properties, trying to infer AC consumption from a whole-home meter introduces too much noise to draw conclusions. Isolating the circuit removes that uncertainty entirely.
Room orientation and size were kept consistent across all three tests to control for solar gain. A south-facing bedroom heats up faster and demands more cooling than a north-facing one of the same size. Keeping these variables constant means the only meaningful difference between test days was whether Voltvert was active.
The results
The table below summarises the recorded consumption across the test period. High-consumption days are those where Voltvert was not active; low-consumption days had Voltvert running normally.
| Date | Voltvert | Consumption (kWh) | Outside temp | Humidity |
|---|---|---|---|---|
| Test 1 — June | ||||
| 8 June | Off | 6.90 kWh | ~24°C | ~76% |
| 9 June | On | 3.30 kWh | — | — |
| 10 June | On | 3.00 kWh | — | — |
| 11 June | On | 2.50 kWh | — | — |
| Test 2 — July | ||||
| 2 July | On | 3.79 kWh | 23°C | 76% |
What about the weather?
This is the obvious question. If consumption dropped because temperatures dropped, Voltvert deserves no credit. So alongside the energy readings, we logged weather conditions using local data for the same dates.
The July readings are particularly useful here. On 2 July — a day when Voltvert was active and consumption was 3.79 kWh — the outside temperature was 23°C with 76% humidity. On 7 July, conditions were nearly identical: 24°C actual temperature, 79% humidity, largely sunny with 0% precipitation. The weather did not explain the difference in consumption. The behaviour of the AC unit did.
The key point: comparable outside temperatures on both high-consumption and low-consumption days means the weather was not the variable. The only thing that changed was whether Voltvert was managing the AC runtime.
It is also worth noting what a 1.2 kW unit running at 6.90 kWh actually means. At rated capacity, that represents roughly five and a half hours of continuous operation. In a bedroom context, that is the AC running most of the night — exactly the pattern Voltvert is designed to interrupt. The device does not make the room uncomfortable. It stops the unit once the room has reached temperature and limits unnecessary cycling in the early hours when the guest is asleep and ambient temperature has already dropped.
What this means in practice
A reduction from 6.90 kWh to an average of around 2.9 kWh per day, per bedroom, represents a meaningful saving at any electricity rate. At a typical Spanish residential tariff of around €0.20–0.25 per kWh, that is roughly €0.80 per bedroom per day. Across a peak summer of 90 days and even a modest property with four bedrooms, that is in the region of €290–360 saved in a single season from electricity alone — before accounting for reduced wear on the compressor.
These numbers are conservative. They are based on early test data from a handful of days. Properties in more extreme heat, with less efficient AC units, or with guests who are particularly liberal with the remote will see a larger gap between the with-Voltvert and without-Voltvert readings.
What comes next
The tests described in this article are a starting point, not a conclusion. The same methodology — dedicated power monitors, comparable bedrooms, weather-logged control days — begins across four Ibiza villas from 26 May 2026. The rooms share consistent parameters: similar size, same orientation, equivalent AC capacity.
By the end of the season, we will have data covering June through September across multiple properties and occupancy patterns. That dataset will capture variation in how different guests use AC, how heat peaks in July and August affect baseline consumption, and whether the savings hold consistently across different weeks and room configurations. Results will be published here as the season progresses.
The same conditions that make Ibiza a useful test environment — high summer temperatures, high humidity, guests arriving from cooler climates — apply equally across the Costa Blanca, Costa del Sol, the Balearics, and much of coastal Southern Europe. The physics does not change. What changes is how much there is to save.
- Power monitors isolated AC consumption from all other loads — the readings reflect the air conditioner only
- Peak consumption without Voltvert reached 6.90 kWh in a single bedroom on a single night
- With Voltvert active, the same bedrooms consumed between 2.50 and 3.79 kWh — a reduction of 45–64%
- Weather data confirmed comparable outside temperatures on both high and low consumption days, ruling out cooler conditions as the cause
- Extended testing across four Ibiza villas begins 26 May 2026 — full seasonal data will be published as results come in
Context and limitations
The figures in this article reflect Ibiza's climate: a long, hot cooling season running from late May through September with consistently high guest occupancy. Properties in cooler climates or those with shorter peak seasons will see proportionally smaller savings. Voltvert is designed for split-unit AC systems and is not compatible with ducted central air or building management systems. Properties with significant vacancy gaps between bookings will also see different results from those reported here.
If our bedrooms were using 6.90 kWh a night, yours probably are too.
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