MeacoCool Cirro+ 16000 (Cooling + Heating, Inverter)

For the largest rooms, the Cirro+ 16000 offers far more cooling headroom than the 9,000 BTU Meaco or 11,000 BTU De'Longhi, yet Meaco rates its Super Quiet mode at just 45 dB - unusually low for a unit this powerful, and quieter than either pick above. It sits at #3 rather than higher because that capacity is genuinely wasted (and can leave a room clammy) below about 30 m2, and it is a large, ~£660 unit, so the value case only makes sense for big spaces. The inverter compressor - which Meaco says lowers energy consumption by up to 35% on selected units - softens the running cost of a big machine versus fixed-speed rivals, and it doubles as a winter heater. If you want the same 45 dB quiet mode for a medium-large room at lower cost, the non-inverter Cirro 12000 (cooling + heating) is a sensible step down at an indicative £539.99.