2 kW or 2.5 kW?
Both sit inside the same CHOICE range, so the room decides. A 2 kW unit suits the lower end: a small, well-insulated room that doesn't get much sun. Rinnai's buyers guide lists 2.5 kW as the most common size for small rooms, which leaves a little in reserve for the hottest and coldest nights.
Rinnai says an under-sized system often can't keep up and wears out sooner, while an over-sized one short cycles, switching off before it has pulled the dampness out of the air.
When a small room needs a bigger unit
Floor area is only the start. Rinnai says higher ceilings demand more and a sun-facing room can need extra cooling in summer. ActronAir's rule of thumb climbs from 150 watts per square metre under a 2.4 m ceiling to 175 watts under a 3 m one.
A small bedroom with a high ceiling, a big window or afternoon sun can outgrow 2.5 kW, so read the 3.5 kW page too, or run your measurements through the size calculator.
A bedroom unit runs at night, so plan for quiet
The energy rating label lists noise figures for the indoor and outdoor units. Mitsubishi Electric says those are sound power levels, and lower numbers mean quieter running.
The outdoor unit matters as much as the one above your bed. In Victoria, cooling mustn't be heard inside a neighbour's habitable room after 11pm, and heating after 10pm. Other states have their own rules, covered in our noise guide.
Ask about a night or low energy setting too. Mitsubishi Electric's i-save, for example, runs 2 to 3 degrees warmer in cooling, or cooler in heating, while you sleep.
What you can sort out, and what the installer does
You can
- Measure the room and note the ceiling height and which way the window faces.
- Compare the noise figures and the stars on the labels of the models you're offered.
- Suggest an outdoor spot that's away from a neighbour's bedroom window.
Leave to a licensed installer
- Confirming the size with a heat load rather than a guess.
- Mounting the outdoor unit level, with air around it and room to service it.
- The refrigerant and electrical work, which is all licensed.
Questions to ask about a bedroom split
- What are the indoor and outdoor noise figures on this model's label?
- Where will the outdoor unit sit, and how close is that to the neighbours' windows?
- Is 2.5 kW still right once you count the ceiling height and the window?
What we'd do
If it were our bedroom
For a room under about 20 square metres with a normal ceiling, we'd choose 2.5 kW over 2 kW and put our effort into noise: a quiet model on the label, and an outdoor unit that isn't under anyone's window. If the room gets the afternoon sun, we'd have a split specialist, someone who fits bedroom units every week, check whether 3.5 kW fits better.
