Air-Con Automation, Efficiency and Electrical Costs

I'm trying to figure out what is the best approach to air-con home automation and temperature settings while keeping the electricity costs down.

I have added foam weather stripping to all the windows and doors. There is reflective tint on the windows and I have blackout shades/curtains on the way. 2HP split inverter air-con in use.

Spoiler: Home Automation Description

My current automation setup looks like this:


The thinking behind this:

0700: Air-con turns on @25°C (usually when outside temperature hits 27°, the sun starts to hit with some force and the inside temperature starts to rise)

1700: Temperature adjusts to 27°C, floor fan kicks on. (outside temperature usually drops to or below 27° at this time and the sun isn't beating down directly on the house, but without the air-con the temperature will creep up.)

2000: Air-con turns off and windows are open. (Outside temperature is usually 26° or below and a floor fan gets the job done)

Leaving the house between 0700-2000: temperature set to 28°.

Returning home sets temperature to 25°, 27° or does nothing depending on the time. It takes about 15 to 20 minutes to get the house to the desired temperature during the day.

With my current setup I'm expecting an electrical bill between P3500 to P4500.

My question is concerning what should be done when I leave the house: is it better (meaning cheaper) to have the temperature set to 27° or 28° to keep the humidity down and walls/floor cool or to just turn it off when go.

Today I tried turning it off while I was away for a few hours. The inside temperature got up to 30°. It took about 40 minutes running at full blast to get the house back down to 25° (about twice as long as it takes when the temperature is set to 27-28° while I'm gone).

I suspect that keeping it running, but at a higher temperature, may be the cheaper option but I'm not sure. If there is any other suggestions for keeping costs down they would certainly be welcome.

 

It isn't warm right now but it just started raining. I don't think it would have cooled down that much in the last 5 minutes but I'll check again next time the sun is out.

 

The different air-con modes are not fully compatible with my home automation. It could be done but it would be a pain to program.

I would also think that the dry mode would require the compressor to be on...which I believe uses the most electricity.

I go back and forth between thinking I should just always leave the air-con on (the compressor rarely turns on after 8pm and the air-con fan likely uses the same electricity as my floor fan) or turning it completely off at night or when I'm away. I think a regular temperature and humidity will extend the life of a lot of things in the house. Less rust, less fungus/mold, less wood always expanding and contracting, electronics running more efficiently, better health from the body and mind operating in a more comfortable temperature/humidity. The long term costs need to be factored in as well as the monthly short term costs but this would be very difficult to calculate.

 

We just use a fan through the day but at bedtime turn on the air-con in our Master bedroom and during the day try to keep our Master bed-room door shut and it stays cool enough through the day. Still does get humid in afternoon so we run a fan in that room as it is also our TV go to.

Prior to bed we switch off the fridge, and in the morning turn it back on. Things remain cool and don't thaw.