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I have a brand-new A+++ inverter – does it still lose efficiency when dirty, or is it 'smart'?

Editorial guide · Updated 18 September 2026

In short Short answer: the inverter adapts compressor speed to how much cooling is needed – but when the evaporator and condenser are dirty, 'how much is needed' rises because heat transfer is weaker, so the inverter simply runs harder for longer. The A+++ label is measured with clean coils; dirt drags it towards A or B without you knowing.

This page explains a situation in an editorial format. It is not an open discussion board or a verified customer review. Contact us on WhatsApp about your own appliance.

Situation discussed

I replaced an old unit with an A+++ Mitsubishi inverter (12,000 BTU) in the bedroom, Băneasa, a year ago. The salesman said 'the inverter adapts, it uses only what it needs'. So dirt does not affect it like the old one, right?

Editorial explanation · Revizie AC

What is really happening

The physics is the same for inverter and on/off: heat passes through the aluminium fins of the evaporator and condenser; a layer of biofilm, dust or fluff is insulating and reduces airflow. The inverter compensates by raising speed – i.e. exactly the consumption you were praising. A dirty filter costs 5–15% regardless of technology; a dirty outdoor coil raises condensing pressure on any compressor. The inverter's real advantage is that, with clean coils, it modulates finely and uses little at part load – which is why it is worth keeping clean more than an old unit, not less.

Explanatory diagramEstimated energy: power × time
Estimated energy: power × time
  1. Average electrical input, in kW.
  2. Operating time, in hours.
  3. Estimated energy, in kWh; actual use varies.

BTU describes thermal capacity, not electrical consumption directly.

What the studies say

What we do on site

  1. At one year in a bedroom the first sanitising is light and quick: sealed double cover, alkaline detergent, adjustable pressure wash of evaporator, roller, pan and hose; sanitising; filters (fine ones included, if the model has them).
  2. Outdoor unit washed in place – one year on a Băneasa balcony already leaves a visible layer.
  3. We do not touch the refrigerant circuit, flare joints or inverter board – nothing warranty-related.
  4. Dated photos for the warranty file. See current rates on the Prices page.

What you can do yourself

  • Filters every two weeks – on an inverter they are 80% of the retained efficiency.
  • Enable the automatic dry-after-shutdown function if the model has it (many Mitsubishis do).

What NOT to do

  • Do not confuse 'smart' with 'self-cleaning' – the 'self clean' function only dries the evaporator, it does not wash it.

Prevention

Inverter in a bedroom: annual sanitising from the second season; filters every two weeks; 'self clean' after every night.

When to call us

0764 012 943, WhatsApp, Monday–Saturday 08:00–20:00; Băneasa is close.

Old outdoor unit covered in dust and dirt on the façade of a Bucharest apartment block
Old outdoor unit covered in dust and dirt on the façade of a Bucharest apartment block
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The information on this page is educational and based on cited sources; it does not replace medical advice. We do not do repairs, installation or refrigerant circuit work.