^ not sure I would call it a huge increase in elec bill. But sure its going to cost you a few extra quid.
Do the math, and NO you can not just look at the wattage of your power supply and say well guess it uses 600watts... That is what the power supply is rated for, not what the PC draws 99.99999% your using it.
So as I type this post, I look down at my ups and drawing .065 kilowatts, if I turn off the monitor it drops to .040. So do the math, my monitor turns off in 5 minutes of idle time.. Don't forget that depending on how long you use your computer comes into play here you should only count the extra cost of not turning it off.
Lets say you only use the computer for 2 hours a day, mines more like 18
But lets say its a normal person couple of hours a day usage. Now turn off your monitor for sure. Mine drops to 40 watts, so X my cost of elec which is about .125 kwh x 22 hours a day = (.04*.125*22) = $0.11 a day to keep my machine on when not using it. x 30 = $3.3 dollars extra a month if I only used my computer for 2 hours a day and left it on the rest of the time.
That extra cost goes way down depending on how much time you actually use your machine. But don't think $3 is going to break anyone, nor would I call that a huge increase in elec bill.
Sure you could use standby which would lower it way more!!! But every now and then by box has issues coming out of standby, not worth the hassle for a couple of bucks a month.
Now I show the cost in the UK for elec a bit higher than here in Chicagoland, I show 0.175 vs my 12.5 cents. So cost you what less than 5 quid??
Yes leaving any elec on when not used is going to cost you, but do the math!! Your more than likely taking cents not dollars.. I would really suggest you pick up a killawatt meter and look to see exactly what something uses in elec.
btw, here is what I am talking about for a killawatt meter, it allows you to plug in any device that uses elec and monitor how much it uses over time, right at the moment, etc. So you could let it run for a few days while you use your computer and get an exact figure for how much it cost per day.
for example its been plugged into my N40L for quite some time, this is my NAS, my router, linux box and a bunch of other VMs that I play and test with. It is on 24/7/365 for SURE!! So far 6632 hours its been on and used 372 Kwh, So 6632 hours = 276.333 days, now in that time it has used 372KWH or 372/276 = 1.34 Kwh per day. So x my 0.125 cost per kwh = 0.1675 cents a day to run.. X 30 = 5 bucks! Cost of cup of coffee or a beer at local pub. I don't see how this is going to be breaking anyone's bank??
Now maybe you got some crazy supped up machine that idles using 300Watts? Then ok you might want to look why that is -- a killawatt is great tool to have if your looking to understand the cost of running different elec items. Or whole home unit as well, I have meter that gives me what the total draw of the house is at any given moment, and logs it over time, etc.. right now the house is drawing 684 watts.. Man does that spike up when running all the appliances, got elec stove/oven -- most everything is elec. So I clearly understand keeping an eye out for what your using.. But sorry leaving a pc on is not going to be the biggest waste in the house.