What you need to know
- Correct sizing matters more than chasing one headline efficiency number.
- A lower thermostat setting can increase runtime without improving comfort proportionally.
- Shade, insulation, doors and windows can change the cooling load significantly.
Use your own measurements
Use the linked BricoDato resource to check these inputs in your own situation. Air conditioning efficiency is affected by outdoor temperature, room heat gain, airflow, installation and the thermostat.
Start with sizing
An undersized unit may run almost continuously and struggle to reach the setpoint; an oversized unit can cycle poorly. Use room volume, exposure and insulation as a first estimate, then check the manufacturer sizing guidance.
Choose a realistic target temperature
The larger the difference between outdoor and indoor temperature, the harder the system must work. Aim for comfort rather than the lowest possible setting and use fans or shading to improve perceived comfort.
Reduce heat before cooling it
Close blinds on strong sun, seal obvious air leaks and avoid adding unnecessary internal heat. These measures reduce the load without changing the air conditioner itself.
Compare habits with the same conditions
When testing settings, compare similar weather, hours and occupancy. Note runtime and kWh if you have a meter or smart-energy record.
A controlled test for air-conditioner settings
Air conditioning efficiency is affected by outdoor temperature, room heat gain, airflow, installation and the thermostat. A setting that seems economical on a mild day can produce a different result in a heatwave.
Example to adapt
For an illustrative test, record total electricity use over two comparable 3-hour periods, each with the same room closed to direct sun. If one session measures 2.1 kWh and another 1.8 kWh, the difference is 0.3 kWh. At €0.20/kWh that is €0.06, but the comparison is only meaningful if weather and occupancy were similar.
| Before changing settings | Check | Reason |
|---|---|---|
| Room | Doors, blinds, sun exposure | Heat gains can dwarf a small thermostat change |
| Equipment | Filters and unobstructed airflow | Poor flow can reduce performance |
| Measurement | kWh over comparable sessions | Instant watts alone can mislead |
Checks before acting
- Use blinds or shading to reduce solar heat before lowering the thermostat.
- Start with a comfortable, moderate setpoint and avoid constant unnecessary adjustments.
- Keep filters clean according to the manual and allow good airflow around the indoor unit.
- Record both comfort and measured kWh; do not optimise the bill at the expense of safe indoor conditions.
Final check
A lower utility bill is not proof that one thermostat setting saved energy: weather, shade and time at home may also have changed. For a useful test, log the outdoor temperature, indoor start temperature, target setting, hours and metered kWh on comparable days. Record whether blinds were closed and whether doors were left open. Do not block airflow or attempt refrigerant repairs yourself.
- Check room size and exposure.
- Use a realistic thermostat setting.
- Clean filters and keep airflow unobstructed.
- Compare kWh over similar days rather than one short reading.
Keep a small job sheet
Log start/end temperatures, setpoint, outdoor conditions, duration, kWh and occupancy.
Turn the guide into a decision
Compare several similar days with one deliberate change, such as shade or setpoint. If the unit repeatedly fails to reach its target or leaks water, check the correct filter procedure and seek qualified servicing rather than lowering the temperature again.