Room sizing, heat gain, airflow and placement explained without relying on a single square-metre rule.
One wall-mounted indoor unit is designed to condition the air it can circulate in its own zone. It may influence an adjacent open area, but closed bedrooms will not receive controlled, even cooling.
The outdoor unit needs required clearances, stable support, drainage, service access and a location that manages sound, weather and neighbour impact. Hiding it completely can restrict airflow.
The best indoor position gives clear airflow across the occupied zone, meets manufacturer clearances, avoids a constant draught and allows a sensible service and drain route.
A heat-load survey estimates the cooling and heating duty from room geometry, fabric, glazing, sun, occupancy and equipment, then tests whether a proposed system and route are practical.
An undersized system may run continuously, struggle during peak heat and fail to reach the target temperature. Continuous operation alone is not proof, because inverters are designed for long steady runs.
An oversized system can cool quickly then cycle or throttle at its lower limit, causing uneven comfort, extra noise and weaker moisture control. Modern inverters reduce but do not remove sizing risk.
A 3.5 kW system may suit some larger bedrooms, lounges or offices, but there is no universal coverage figure. The result depends on the calculated peak load and matched model performance.
A 2.5 kW label describes nominal cooling output, not a guaranteed square-metre coverage. Two rooms of equal area can have very different heat gains.
Computers, monitors and networking equipment release electricity as heat inside the room. A regularly occupied office needs that equipment load included alongside sun and fabric gains.
Open-plan sizing must cover the connected volume and uneven gains from glazing, cooking and occupancy. One unit also needs a clear air path to the parts of the space that matter.
Large windows can add significant solar and conductive heat, especially without external shade. Their orientation, glass specification and exposure matter more than glass area alone.
High ceilings increase room volume and can affect air distribution, so a floor-area shortcut may understate the duty. Construction and occupied-zone comfort still need consideration.
South-facing glazing can raise solar gain, but the effect depends on glass area, external shade, curtains and the hours of direct sun. It is an input, not an automatic capacity uplift.
Loft rooms can have high roof and solar gains, limited wall space and unusual ceiling volume. Sizing should account for insulation, roof windows and the hottest occupied period.
Conservatories often need more cooling than a normal room of the same floor area because the roof and glazing admit substantial solar heat. Orientation and shading can dominate the result.
A calculator can provide a screening estimate when its assumptions are visible, but it cannot see shading, construction, airflow or the proposed route. Treat the result as a starting range.
Cooling capacity may be shown in BTU per hour or kilowatts; 1 kW is approximately 3,412 BTU/h. Converting units does not complete the heat-load calculation.
Many bedrooms suit a small wall split, but square metres alone are not enough. Glazing, roof exposure, orientation, occupancy and the system's minimum output all affect the right choice.