Don't laugh at the idea of ice cubes. I wish I had the source, But I have read of american city towers using ice cubes to supplement the cooling systems during summer, because when the ice cubes get VERY large, they are tremendously efective (way more effective than normal air conditioning heat exchange units). At the end of the day, the melted ice is still cool and easy to refreeze. The total energy savings are quite substantial. Maybe if you're interested you can google it up ( =

And this is key ( =

The tariffs for off peak hours would be lower too, so money is definitely saved.