Start with how the room gains heat
Portable air conditioners are often sold using a simple room-size chart. That can be a starting point, but two rooms with the same floor area can need very different cooling output.
The factors that matter
- Glazing and sunlight: large south- or west-facing windows can add substantial heat.
- Insulation: poorly insulated rooms warm faster and are harder to hold at a comfortable temperature.
- Ceiling height: a taller room contains more air than the floor area suggests.
- People and equipment: occupants, computers, televisions and cooking equipment all release heat.
- Room use: a shaded bedroom and a sunny conservatory present completely different demands.
- Exhaust sealing: poor window sealing lets warm air return and reduces effective performance.
The practical starting point for many bedrooms, living rooms and home offices.
Additional output for larger living spaces, offices and warmer or more demanding rooms.
Bigger is not the only answer
More output can help a difficult room cool faster, but setup still matters. Keep the exhaust hose as short and straight as practical, seal the window opening, reduce direct sunlight and avoid placing the unit where furniture blocks airflow.
Questions customers ask
What does BTU mean on an air conditioner?
BTU per hour describes the unit’s cooling output. A higher figure means more cooling capacity, but the correct choice still depends on the room and its heat load.
Is 12,000 BTU enough for a bedroom?
It can be suitable for many bedrooms and home offices, but large glazing, poor insulation, direct sun and high ceilings can increase the output required.
When should I consider 14,000 BTU?
The higher-output option is more appropriate for larger living spaces, offices, conservatories and rooms with higher heat gain.
Does a portable air conditioner need a window?
It needs a suitable route for the exhaust hose. A window kit helps reduce warm outside air returning to the room.