how much electricity ...............?

Question

in minutes does it take to switch on the tv - ie how long can I leave the tv on without using more electricity than switching it on and off,
same question applies to computer as well

Answer 1

In very old TV's, when the unit was turned off, all power was lost. In many modern sets, some of the circuits are maintained energized to speed up reception of the picture when the unit is turned on. That is like a "sleep" mode that draws reduced power and also saves the tube. Turning the TV on and off too frequently can shorten the life of the tube. Whether you should leave your TV on or off should depend in part on how long no one will be watching it rather than whether everyone has left the room for a while. Shutting off the TV when no one is going to watch it of course always saves power and money on the power bill.

Many modern computers automatically go into a low power sleep mode when not disturbed for a set period of time. Some say that each startup of the computer results in a surge through the computer chip(s) that can reduce chip life. Therefore some people leave computers on (even over night) unless they will not be used within a reasonable time. Nameplates on TV's and computers should indicate the watts of power consumed. For a rough idea of the amount of power, compare the unit's rated watts to an equal number of 100 watt lightbulbs. Ten 100 watt lightbulbs burning for ten hour consumes 1,000 watts or one kilowatt which costs roughly 10 cents per hour.

Answer 2

Sorry, I don't have an exact answer for you. It depends on many factors. In general, any surges in current will be very brief (probably less than one second) when an electronic device such as this is turned on and capacitors charge up, coils develop magnetic fields, etc. When you average this current surge out over time, it probably only takes a few seconds of "steady state" operational time to draw the same amount of electricity as was drawn during the brief "power on" surge.

A computer might be a little different, since when you turn a computer on, the hard drive motor spins and data is read off of the drive to get the system booted up. The hard drive might run for 30 seconds or a minute before everything is booted up...it really depends on the system. The drive motor isn't a huge consumer of power, but it will take more "on" time to offset the additional startup power than a TV would.

In either case, I'd suspect you are talking about less than a minute...meaning if you are strictly looking at saving electricity, you should turn the device off if you are leaving the room for more than a minute. As a practical consideration, though, you'd leave these devices on for relatively short periods of time. Turning an electrical device on stresses the parts and can cause them to fail sooner over time (much like many ordinary light bulbs burn out the instant you turn them on, rather than just burning out in the middle of use). Not to mention, many people would rather not wait a minute or two while their computer reboots if they shut it off every time they left the room.

Answer 3

Modern switch mode power supplies (SMPS) actually use less startup power than the old linear ones (on electronic stuff older than about 1980). So I would reccomend just turning off most electronics when you are not using it. As for computers, the jury is still out, as to whether to leave them on. They have hard-drives which are mechanical. Leaving them on all the time may have some benefit, but turning them off after each use also has some benefit. I say, if you are not going to use a computer for more than a week, turn it off (like if you go on vacation or something.) Otherwise, just leave it on, or on standby/suspend (if your computer has that option.)

To get the energy usage of some appliance or device (if you want to calculate it) you look at the back panel, near where the electrical cord comes out of it. Usually there is a plate that gives the rating of the appliance. Sometimes the instruction manual gives that information too. Its going to say something like:

120 VAC
300 mA
60 Hz
36 W


Or something like that.

If you see something like 400 W, that means the appliance consumes 400 Watts of power. An 100 W lightbulb consumes 400 W of power. If you run this appliance for 1 hr, it will consume 400 Watt-hours (400 Wh). In the US electric bills are charged by the Kilowatt-hour (kWh) or every 1000 Watt-hours. The usual rate in the US is about 10-12 cents per kWh. For example your tv back panel says:

120 VAC
200 mA
60 Hz
24W

If you run it for 10 hours, it will consume 24W * 10 hrs = 24*10 W-hrs, or 2410 W-hrs. Divide by 1000 to get the kWh, because 1000 Wh = 1 kWh. So thats 2.41 kWh or, rounding up, about 3 kWh. So cost would be 10 cents (because its 10 cents per kilowatt hour) * 3 kWh = 30 cents.

Answer 4

If you are thinking that there is a brief surge in current as you switch any device on and therefore it may be better, form the point of view of poer consumption, to leave it on rather than switch it off for a period and then back on, don't worry. The surge on switch on is very short and you are going to save power all the time it is switched off.

It is sensible to leave devices switched on rather than switching them on and off every few minutes. The reason for this is the internal stresses on components that occur at switch on and switch off. These days, even that is not he issue that it once was.

I would suggest that if you want to save power, switch it off if you are not using it for an hour or so. Also, do not forget all those little phone chargers and othe rsupplies that we leave plugged in all the time. They eat up lots of power when doing nothing.

Answer 5

It's it not just the electricity bill that you have to keep in mind. The more important factor is the stress the circuitry of the device goes through everytime it is switched on and off. That has economic cost as well.

Answer 6

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Answer 7

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