Advice
10 air conditioner buying and installation mistakes that cost money
Most complaints we hear in service are not about faulty units but about decisions made before and during installation. Ten of them repeat constantly, and each is easy to avoid.
5 min readUpdated
1. Capacity by feel instead of by calculation
Undersized runs flat out and still fails in a heatwave; oversized cycles, does not dehumidify and costs more. Use 100–120 W/m² with corrections, or our calculator.
2. Buying "A+++" without checking which mode
Many models are A+++ for cooling and A+ for heating. If you heat, SCOP decides the bill.
3. Saving on installation
Installation without a vacuum pump leaves air and moisture in the system: efficiency drops, the compressor wears and the warranty is void. A proper job vacuums below 500 microns and leaves a report.
4. The indoor unit above the bed or sofa
Cold air straight onto people means summer colds and draughts. Air should pass beside the seating or sleeping zone.
5. The outdoor unit in full sun or an enclosed space
Full south sun costs up to 10% in a heatwave; a glazed loggia recirculates hot air and trips the protection. A canopy or a north/east wall solves it.
6. A long pipe run for looks
Every metre beyond 5–7 m reduces output and costs 30 €/m. The shortest route is almost always the best.
7. No condensate drain
The indoor unit produces litres of water a day in summer. Without a sloped free outlet the water comes back and drips down the wall; plan a pump where there is no natural drain.
8. Ignoring noise
19–22 dB in quiet mode is bedroom comfort, 30 dB is a problem. Do not mount the outdoor unit under a bedroom window.
9. Years without maintenance
Clogged filters and a dirty coil cost 15–20% more electricity and cause smells. Wash filters every 2–4 weeks; a technician cleans the coil once a year.
10. Buying at the peak of the season
Late June: highest prices, lowest stock, weeks of waiting for installation. Plan in spring or autumn.
Frequently asked questions
What is the most common cause of failure?
Improper installation and no maintenance. Factory defects on Japanese brands are below 1%.
Is the warranty void with an uncertified installer?
With most manufacturers, yes, without a certified installation report. Keep the report and invoice with the warranty card.
Useful links