How much will it cost?

[lynbrown]

if i put my computer on in the morning and leave it on all day, will that be more expensive than putting it on and off several times during the day ?

[NazNomad]

Leaving it on will be more expensive than stop/starting it ...

[NazNomad]

impossible to say how much as you've given no details of your power supply.

[seadogg]

Check your power settings in the control panel. It will use less, I think, if you set it to go into hibernation after a short inactivity time

[TTG]

If you are doing full virus scans or other lengthy jobs (without needing your input in the middle) I always turn off speakers and screen. Saves a little power!

[Mobius1]

If left on, it will almost certainly use more power than if turned off, but there's no definitive answer to this question in the form that you've asked it.

Repeatedly turning your PC on and off will put more wear on the components of it than just turning it on and leaving it running. There are lots of power saving options on today's PCs and laptops. Screensaver, automatic monitor turn off, self adjusting processor clockspeeds and fan levels.

If you want to reduce power usage but still be able to use your computer sporadically I suggest putting the computer into "sleep" mode. This will put most all of it's components into a powered down or lower power state but make it so that the PC can be bought back to life at the touch of a keyboard stroke, and will retain things in memory so you're not booting up the operating system each time you use it.