Running a modern inverter air conditioner overnight typically costs between €0.50 and €0.65 for eight hours of use, according to data from Selectra.info. This cost varies by device type, with portable units costing significantly more—roughly €1.71 per night—due to a lack of modulating technology that regulates energy consumption once a target temperature is reached.
Why does an inverter air conditioner cost less to run overnight?
Inverter technology allows a device to adjust its operating intensity automatically. Once the room hits the set temperature, the system doesn’t shut off and restart; it slows down. Selectra.info reports that when set to 26°C during a cooler night, these units consume only a few hundred watts per hour.
Emma Cousinier, an energy expert at Selectra, explains that turning the unit off before bed can actually increase costs. If the room warms up, the device must work harder and consume more energy to bring the temperature back down. Maintaining a steady state is more efficient than recovering from a heat spike.
How much does overnight cooling cost in Romania?
Costs in Romania fluctuate based on the provider and the specific contractual offer. Based on current market analysis, rates range from approximately 1.06 lei/kWh (competitive offers like Hidroelectrica) to 1.45 lei/kWh for those on universal service regimes.
Using the lowest rate of 1.06 lei/kWh, a full night of sleep in a temperature-controlled room costs between 2.65 lei and 3.40 lei. Even at the higher rate of 1.45 lei/kWh, the cost remains under 4.64 lei per night. It is important to note that electricity price caps in Romania ended on July 1, 2026, meaning consumers are now paying these updated market rates.
Comparison: Energy Consumption by Device Type
The type of cooling hardware drastically changes the nightly bill. The following data, based on French regulated tariffs of €0.194/kWh, highlights the disparity in efficiency:
| Device Type | Energy Use (8 hrs) | Estimated Cost/Night |
|---|---|---|
| Fan (50 W) | Low | €0.08 |
| Split Inverter AC | 2.5 – 3.2 kWh | €0.50 – €0.65 |
| Portable AC | 8.8 kWh | €1.71 |
How to lower your cooling bills during a heatwave
Efficiency isn’t just about the machine; it’s about the environment. To prevent energy spikes, Selectra.info suggests four primary tactics:
- Manage Sunlight: Close windows and blinds during the day to keep the interior cool.
- Maintain Hardware: Clean filters periodically, as dirty units consume more electricity.
- Improve Insulation: Poorly insulated homes lose cold air quickly, forcing the AC to work harder.
- Use Timers: For portable units, set a timer to shut the device off two hours after falling asleep.
FAQ: Sleeping with Air Conditioning
Is it cheaper to turn off the AC before bed?
Not necessarily for inverter models. According to Emma Cousinier of Selectra, turning it off may cause the room to warm up, requiring more energy to cool it down again later.
What is the ideal temperature for energy saving?
Setting the unit to 25°C or 26°C is recommended to balance comfort and cost.
Why are portable ACs so much more expensive to run?
They lack the modulating inverter technology found in split systems, leading to higher kWh consumption (8.8 kWh vs. max 3.2 kWh for a split unit over 8 hours).
Want to lower your utility bills? Share your best energy-saving tips in the comments below or subscribe to our newsletter for more expert analysis on home efficiency.
