Lowering temp to save electricity

[Loki]

I'm sure this question has been asked a lot but is it more economical to leave the temp at 100 and turn it up to 104 when you get in or leave it lower say 90 and turn it up to 104 each time

[goneaway]

This method works for me, but only because I utilise the free energy from my solar PV Panels.
I turn the temperature down to 25°C on Sunday night, and then back up to 38°C on Friday morning when the sun is shining and giving me free power.

On the other hand, I have heard people mention on here that it makes no sense to turn it down.
The energy saved, is only spent again when trying to bring the temperature back up.
I imagine the only way this would work, is if you live in a warm environment (say California), where the water temperature would take a long time to fall.

I'm sure a mathematics genius will be along shortly with an equation.

[bob snader]

I imagine the only way this would work, is if you live in a warm environment (say California), where the water temperature would take a long time to fall.

Yeah, it would depend on the climate. I'm in Manitoba where Winter temps can get down to -40. If I turn it down it takes too long to warm up again