CFL Bulbs Is this costing me money

And the 'pooter?

My PC+19" monitor is 80W on idle; just built a new system for a friend and it's the same wattage with a 22" screen. 12h a day is near enough 1kWh, 7 days a week, >300 days a year...

Measured how though ? The figures for the stuff that's 10, 12 even 25 years old is largely irrelevant, as back then, care was not taken over designing standby modes with power saving in mind. In the grand scheme of things, most of those standby powers are quite small (and in reality, may actually be even smaller). The entire lot added up for a day, could probably be mitigated by boiling one kettle, or heating up one ready meal ...

Arfa

Good heavens - my 5 year old LCD is 50 watts on and 3 on standby.

(not sure you are right to use kWh - kW yes, but not kWh

He's right ... 80 watts x 12 hours = 960 watt-hours = 0.96kWh

I agree with you! Absolutely but the previous person said, "12h a day is near enough 1kWh". It isn't - it is 0.96kWh

Not trying to be pedantic - but it makes a big difference if you start to cross reference to other information.

Lesson:

500 watts running for one hour = 0.5 kilowatt hour.

80 watts x 12 hours = 960 watt-hours = 0.96kWh

Sorry - isn't 80 watts equal to 0.08 of a kilowatt - therefore after 12 hours this is 0.96 of a kilowatt consumed - at a rate of 0.08 kilowatt hours.

Somebody help me!

From Wikipedia

"Note that the kWh is the product of power in kilowatts divided by time in hours; it is not kW/h."

I'd say within 5% is near enough in this context.

"Note that the kWh is the product of power in kilowatts multiplied by time in hours; it is not kW/h."

(cut and paste from Wikipedia, at 13:40 22/2/09)

leading to 960 watts being consumed after 12 hours. - but still 0.08 kWh

Well that's confusing (i.e. getting utterly wrong) 'product' and 'divided'.

kWh is the product of kilowatts *times* hours.

Adam

You may just have been unlucky - some clueless numpty on 83.70.166.120 put that change in there this morning. Fixed this afternoon.

Simple,

Some STB's etc use about the same energy on standby as in operation

Actual hours TV watched may be 2-5 hours.

So standby hours = 19 - 22 hours (if maximised by the user).

Ergo standby consumption can far exceed useful consumption.

Derek

Mmmm. Wikipedia updated today - well done!

Another definition: A unit of electric energy equal to the work done by one kilowatt acting for one hour.

Therefore (I think) 80 watts is 0.08 kWh

I think my mind is getting a bit clearer having looked at it several times now.

Confusing the rate of consumption (spot sample) with total consumed in a given period (for metering)

A watt is a joule per second.

Both watts and kW are units of power ie the rate at which energy is being converted

To find the amount of energy that an appliance has used you multiply the appliances kW rating (it's power) by time (hours) to get kWh.

The kWh is a unit of energy.

So 80W is 0.08kW

People sometimes say "kW per hour" when they should be saying "KWh per hour" eg a 3kW fire uses 3kWh per hour not 3kW per hour.

HTH

Adam

Tracking back - It was changed on 13th Feb. (Never looked at the page history before - interesting)

I am 86.2.159.xx just in case I am a suspect!!

Viewing say 4hrs in the evening @ 80W = 320Whrs. There are 20hrs left of the day in standby, if that standby power is >16W then the set will use more power in standby than it does for viewing.

As has already been pointed out modern kit has very low standby powers (16W.

kW is power; kWh is energy, ~80Wx12h=960Wh, or near enough 1kWh.

A rough estimate for annual consumption is Wx9 (as there are 8760h/year and there's no point in being too precise with something that can be difficult to measure accurately), so a box at 10W (as above) wil consume 90kWh (units)/year. My TV doesn't use anything at all on standby - it wastes 100% of it.