Cost of Air Con

Aircon is the cheapest form of cooling, especially the inverter types which power down but not off so don't waste power by constantly switching on and off.

You will get up to 4 times the amount of cooling (or heating) with an inverter. However, even if you only use 2 euro a day on aircon that will still add 60 euro to your bill each month plus the tax and so on. If you do leave it on all day, make sure you have a programmable thermostat so it virtually stops when the rooms are cool enough. Plus leaving it on all the time will put a lot of pressure on the system and lower the life expectancy but, probably more importantly, the pressure on your wallet.

We have all our windows and doors open to give a nice cooling breeze and just switch the aircon on when it gets too hot. We never leave it on at night either, just an hour or so before going to bed to cool the room down. 

Spanish authorities recommend that aircon be set between 25 and 27 celsius (thats why shops and restaurants are told to set aircon at 27c. during heatwaves)

Setting too low and turning on and off, use way more electricity (and associated costs).

Buy 1 or 2 large fans (usually only use 50w-100w per hour, compared to aircon that can use up to 3000w per hour) and place these to create a crosswind and a simple hint is to freeze a 2litre bottle of water (only fill to 1.5iltre before freezing) and place it behind or in front of the fan, to create a cool breeze.

If you open windows and doors while using aircon, remember that then you are trying to cool or warm the whole of Spain

Although I fully agree regarding air-con being used with windows closed. But it is worth remembering that power assisted fans ( or 2) generates a small amount of heat from the motor. Using ice, helps of course,  but uses power at the point of freezing. V

23c is just nuts and a temperature few would be able, or indeed wish, to achieve!

If you're got them set for that and they are still struggling to bring the temperature down to a comfortable level (typically 26/27c) then either they are just not working properly or are simply too small for the spaces you're trying to cool. 

If you state the make and models of your A/Cs, and a rough estimation of the room sizes, there are ways to work out if they are adequate for the task or not.

Of course some older Spanish properties, and some not so old, are so poorly insulated that keeping them cool or warm can be more of a challenge but even then A/Cs on @23c for 24 hours, and still not doing the job is, definitely not normal. 

If the OP has a fridge/freezer, then freezing bottles of water comes at no extra cost, as the freezer is working anyway. The amount of heat generate by a 50-100w fan is less than that generated by a light bulb or 1tenth of what your computer generates. Do the maths.

I am a retired refrigeration and air conditioning engineer living in the U.K. at the moment it is hot here and I have 4 air conditioning systems in my house, for night time bedroom use I set mine for 23oC and set the timer to switch the air conditioning off after 5 hours

Opening the windows to get a natural draught through out the house works well.

Modern systems are energy efficient and as stated above an inverter system will slow the compressor down to tick over and increase speed as demand requires reducing energy costs and wear.

No  one  mentioned   Ceiling fan  for  cooling  the room,  i  used  .mine  in  Bedroom  last  August   no  big  difference  in  Electric  bill, maybe   I    am   missing  something 

See my post, eh?

I no longer use aircon, (only because I moved house after 20 years with aircon, & happy with it).

I now use an air purifier (water/ice optional). I have noticed that a power fan alone does not "cool" a room (as my thermometer testifies) but helps cool a body purely by its circulatory air effect as with a normal fan. I always sleep with the windows open anyway for fresh air. Each to their own.

V