HVAC Sizing Guide

Sizing HVAC for the Costa del Sol Climate

Sizing a climate system in Marbella, Fuengirola, Estepona or Mijas is not the same as in northern Europe or inland Spain. The Costa del Sol enjoys over 320 days of sunshine a year, long summers with highs above 30°C from June to September, and mild winters that rarely drop below 8°C. As a result, the cooling load almost always comfortably outweighs the heating load — and a system sized from cold-climate tables ends up oversized for winter and frequently mismatched for summer.

Coastal humidity is the most underestimated factor. Proximity to the Mediterranean keeps relative humidity above 65% in summer, which makes the air feel hotter than the thermometer reads and forces the system to dehumidify as well as cool. An oversized unit chills the air within minutes, shuts off before it can remove moisture and leaves a cold-but-clammy room, while the short cycling wears out the compressor and pushes up running costs. A unit that is too small, on the other hand, will run flat-out through August without ever reaching the target temperature. That is why we recommend a real heat-load calculation (Manual J-style) rather than the quick square-metre rule of thumb.

Property type also changes the outcome. A detached villa catches direct sun on all four elevations, usually has high ceilings, open-plan living and large glazed areas, so it typically needs a multi-split or VRF system split into zones to handle bedrooms, living rooms and daytime areas separately. Penthouses add solar gain through the roof. A mid-sized apartment is shielded by neighbouring units, gains and loses less heat, and is well served by a more compact split or multi-split. Orientation (south and west add load), insulation quality and glazing type then fine-tune the exact capacity — the inputs captured by the calculator above and confirmed during an on-site survey.