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I have a Dell CRT Screen and the only info I have is this:
AC input
voltage: 90 to 264 VAC
frequency: 50 or 60 Hz + 3Hz
current: 1.5A max. (RMS) at 120 VAC; or 0.8A max. (RMS) at 220 VAC
How can I calculate the energy consumption in Watt-hours for an hour (or better, a day)?
r0ca
Posted 2010-04-07T16:26:14.980
Reputation: 5 474
3
Power is Voltage times Current, and power consumption is measured by Power times Time.
Note that your CRT's specs show that it will draw one of two currents depending on your location's mains voltage. If your area uses 120V AC, your CRT will draw a maximum of 1.5A; if your area uses 220V AC, your CRT will draw a maximum of 0.8A.
Power consumption for 1 hour:
= Voltage * Current * Time
= 220 V * 0.8 A * 1 hour = 176 Watt-hour
= 176 / 1000 = 0.176 Kilo Watt-hour
To find the consumption for one day, multiply by 24:
0.176 * 24 = 4.224 kiloWatt-hours
This assumes that the monitor is on for all 24-hours. If the CRT is under standby mode, then the power consumption will be lower.
Sathyajith Bhat
Posted 2010-04-07T16:26:14.980
Reputation: 58 436
it also assumes 220V, though it's not hard to adjust for locations that provide 120V AC. – quack quixote – 2010-04-07T17:47:50.870
For modern computer hardware with switched-mode power supplies, the power consumption should be (and according to the posted specs, is) very similar regardless of mains voltage. – coneslayer – 2010-04-07T17:51:32.310
@coneslayer: sure. i'm just pointing out that Sathya's calculation grabs a certain set of values from the specs, and that you could perform the same calculation with the other set of values. – quack quixote – 2010-04-07T18:01:26.860
Guys! I'm impressed by that! Thank you so much! – r0ca – 2010-04-07T18:09:44.157
2Oops! NOTE THAT Sathya's answer is WRONG. (posted again, here, for visibility.)
Yes, the formula is correct, etc, however you CANNOT get power consumption from specifications. What you get from specifications is the rated worst-case, NOT actual. The goal of the specifications is to tell you what the system is rated for.
Take an automobile, for example; just because it's rated capacity is 2500 lbs does not mean that that's what it carries every day. The tires, while rated at 750 lbs each does NOT mean they (collectively) carry 3000 lbs all they time. Do not confuse rating from actual load... – Richard T – 2010-04-07T18:28:41.833
One more point, while Sathya DID cite "standby mode", don't think that the answer is any more correct; In most cases when in actual service (and NOT in stand-by mode), power consumption will be considerably lower than the device is rated. This is true for just about everything that consumes electricity. – Richard T – 2010-04-07T18:32:21.997
@quack quixote Thanks for fleshing out my answer. Thought minimal would be good, but your version is better. – Sathyajith Bhat – 2010-04-08T15:29:37.463
@richardT: you're right, the calculation is worst-case only -- but with the information given this is the only calculaction you can get. there are other power-consumption questions that point out the only way to know actual power consumption is to measure it with a meter.
– quack quixote – 2010-04-08T15:38:19.6301
Therefore:
if running at Max amperage
tsilb
Posted 2010-04-07T16:26:14.980
Reputation: 2 492
0
I used to have three 21" pro monitors. They came with 3A fuses. One day a fuse blew and I tried a 1A fuse. It blew as well. So each monitor used more than 240W.
Ohms law is V x A = W
So 240V x 1A = 240W and the fuse blew, but a 3A fuse was ok (240V x 3A = 720W), so it's greater than 240W but less than 720W - that's quite a range, and also you have to bear in mind that this will peak with a surge when the monitor is turned on - I think 250W each monitor would be a good estimate.
I changed them for three 26" 16:10's which are 52W each so quite a saving from 750W apx total down to 156W :)
sarah
Posted 2010-04-07T16:26:14.980
Reputation: 1
r0ca, this is much more specific and to-the-point than your question from yesterday, so i'm leaving it open. but stop posting the same question multiple times. if you need to rephrase a question, use the "edit" function. – quack quixote – 2010-04-07T17:50:34.217
Oops! NOTE THAT Sathya's answer is WRONG.
Yes, the formula is correct, etc, however you CANNOT get power consumption from specifications. What you get from specifications is the rated worst-case, NOT actual. The goal of the specifications is to tell you what the system is rated for.
Take an automobile, for example; just because it's rated capacity is 2500 lbs does not mean that that's what it carries every day. The tires, while rated at 750 lbs each does NOT mean they (collectively) carry 3000 lbs all they time. Do not confuse rating from actual load... – Richard T – 2010-04-07T18:28:03.270