Close the windows during the day
A classic saying in Spanish during the summer: a sun that punishes, empty streets and windows shut tight.
Direct sunlight into the house gives so much life, but also makes it really hot, especially for south-facing windows.
So as not to waste energy in air-conditioning, close all outside doors and windows, close the curtains and lower the awnings when the air conditioning is working.
You can also save by choosing which rooms you want to keep cool and closing the others. That way you will not waste energy cooling areas that do not need to be kept cool.
And when it gets cool outside... open everything up and let the air in!
Programme the thermostat and forget all about it
Lowering the temperature when you get home to make it cool down faster is not a good idea.
The contrast between the outside heat and the jet of cold air may affect your health, and the fact is you will not get more comfortable in less time.
Just an expense that really is not worth it.
According to the IDAE (Spanish Institute for Diversification and Energy Saving) each degree you lower the thermostat means an 8% increase in the bill.
Make it all easier because the summer is long. Set the thermostat at around 26º and let the air conditioner do its job.