We have been using a Comfee 7000 btu portable aircon unit for about 4 years to reduce the temperature of our main bedroom to a reasonable 20 to 22 C temperature during heatwaves in north-west France, it’s been 100% reliable.
It came via Lidl and cost about €200 together with the vent kit.
But during the last heatwave this year we had to run it 24 hours a day/night for 4 days straight to keep the temperature down to reasonable levels, so we bought a bigger 12000 btu unit which is capable of dropping the temperature from 26-27 C to the 20-22 C level in about 2 – 3 hours, it came from Amazon and is quieter than the 7000 btu unit.
The window vent kits supplied are a PITA, I made a plywood blank to carry the 150 mm dia warm air outlet hose fitting in the window opening – that will depend on the sort of windows you have, our’s open inwards here.
The moral of the story is don’t buy a small aircon unit and hope it will cope when it’s really hot.