LG WZ12AWN (12,000 BTU, 3.45 kW) - Inverter Pro wall-mounted inverter air conditioner with Wi-Fi

The 12 000 BTU Inverter Pro: the same light pair of units

The WZ12AWN is the 12 000 BTU machine of the basic Inverter Pro series: 3.45 kW of cooling, 3.5 kW of heating and up to 35 m² on the card. The indoor unit is the same as on the 9 000 BTU WZ09AWN (item 1804) - 913 by 309 mm at a depth of 203 mm, weighing 9.2 kg - so on the wall the two cannot be told apart. The outdoor module has barely grown: 770 by 545 by 288 mm and 21.1 kg, while units of this capacity in other series weigh 28-30 kg. For installation that makes it the cheapest way to cover 35 m² in this catalogue: standard brackets, two people, no wall reinforcement. The appearance is neutral - a white panel with no screens or mirrors - which in a rental or a country house is rather an advantage, because there is nothing on it to spoil.

3.45 kW over 35 m²: where the figure works

The 35 m² on the card assumes a regularly shaped room with one external wall and ceilings up to 2.7 m. In such a room the machine reaches temperature in 10-15 minutes and then holds it at low output, which is the most efficient mode an inverter has. If this is a studio with a kitchen, read those 35 m² as 28-30: hob, oven and fridge together add several hundred watts of heat that the same circuit has to remove. In the shoulder season 3.5 kW of heating is enough to hold 21 degrees in a 30 m² room through October, but in this series heating capacity barely exceeds cooling capacity, so a cold November is beyond it. For a 15-18 m² room this machine is oversized: it would cycle in short bursts, and the 9 000 BTU model is the right answer.

What the inverter actually gives you in a basic series

The name Inverter Pro signals the main thing: the compressor does not switch fully on and off but varies its speed, so the temperature holds steady without swings of two or three degrees. The second advantage is more mundane - a start with no current surge: older machines with direct starting produced a brief voltage dip that made lights flicker and electronics reboot. The third is lower consumption at part load: a machine that spends 80 per cent of its time at 30 per cent of capacity uses far less than one cycling on at full power. What an inverter in a basic series does not give you is record seasonal efficiency, because class A+++ needs a larger heat exchanger, and that simply does not fit this casing. Nor should you expect the quietest operation here - 25 dB(A) against 19 dB(A) in the Deluxe series is noticeable at night.

54 dB outdoors - an argument for dense housing

The outdoor module is rated 54 dB(A), noticeably quieter than the 60 dB(A) of the Deluxe series at the same capacity. For a detached house that difference is academic; for a courtyard well or a balcony beneath a neighbour's bedroom window it can be decisive. The physics is simple: a smaller casing with a smaller fan runs at higher speed, but the unit itself is less powerful, so the resulting sound comes out lower. Vibration mounts under the feet and a flexible section in the pipework remove structure-borne hum through the wall - in a panel building that matters more than the decibels themselves. If the unit goes on a balcony, check that hot air does not return to the inlet: a 21 kg machine with a compact coil overheats sooner than larger models in enclosed glazing.

Installation: what to demand of the crew

The run is standard: a 1/4 inch liquid line, a 3/8 inch gas line, up to 15 m in length, up to 10 m of height difference, refrigerant R32. The first thing to demand from installers is evacuation with a vacuum pump rather than purging with refrigerant: the latter is cheaper for the crew and worse for the machine, because moisture and air stay in the circuit. The second is a torque wrench on the flare joints: under- or over-tightened nuts are exactly what produces a slow leak during the first year. The third is a leak test before charging, ideally with pressurised nitrogen; without it the leak is found only after the refrigerant is gone. And finally: insulation on each pipe separately with sealed joints, and a protective duct on the outdoor section, because unprotected insulation crumbles in two or three seasons.

ThinQ in a flat let to tenants

Built-in Wi-Fi and the LG ThinQ app give the Inverter Pro series exactly what a property used by other people needs: scheduling, remote switch-off and the ability to see that the machine is not running around the clock with a window open. The app shows consumption over a period, so it is clear how much the air conditioner really adds to the bill in an active rental month. The router has to provide a 2.4 GHz network - that is the key condition, and it is worth checking before promising guests phone control. A detail specific to rentals: infrared remotes get lost, so app access often turns out to be not a convenience but the only working way to operate the unit. Filters clog faster in this kind of use than at home, so rinsing them every two weeks is the norm rather than over-caution.

Which jobs it fits and where it is out of place

The WZ12AWN is the choice for a country house, a rented flat, a summer kitchen, a study or a living room of 25-35 m² where the machine works for a few weeks or months a year rather than every day for years. Light units and a quiet outdoor module make it suitable for facades and walls that would not carry heavier equipment, and the neutral appearance causes no trouble when occupants change. Where the model is out of place: spaces where the machine runs many hours every day, where the gap between A++ and A+++ accumulates into hundreds of kilowatt-hours a season; a bedroom with strict quiet requirements; a room above 35 m². If heating through the cool months is the main task, a series with a heating bias such as the H12S1D (item 1801) with 4 kW of heat is the better buy. And for a shop or an office with footfall, semi-industrial equipment with even air distribution is the correct answer.

How it differs from neighbouring models in this catalogue

The WZ09AWN (item 1804) is the 9 000 BTU machine of this series at 2.63 kW of cooling for up to 25 m²: the same indoor unit, the same installation, a smaller circuit. The WZ18AWN (item 1806) is the 18 000 BTU Inverter Pro at 5.05 kW of cooling, but already with a heavier 11 kg indoor unit, a 38 kg outdoor unit and runs up to 25 m. The H12S1D (item 1801) is the Deluxe machine of this capacity rated A+++, at 19 dB(A) and with 4 kW of heating: better value in daily duty, but dearer and with a louder outdoor unit. The AC12BK (item 1799) is an ARTCOOL Mirror at 3.5 kW with a mirrored panel and UVnano: the choice when appearance and fan hygiene matter. The A12GA1 (item 1795) is the gallery unit with a photo frame for the same floor area: an interior solution that demands solid masonry for its 16.7 kg.

Tell us how often the air conditioner will run and the floor area, and we will say whether the basic series is enough or a more efficient class pays off.