kwired
Electron manager
- Location
- NE Nebraska
Supply it from a wall switch or turn the breaker off:happyyes:
They probably do consume some energy even when nothing is plugged in, but we need to know more about their design to know for certain.
USB Receptacle
- Thread starter Dennis Alwon
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They probably do consume some energy even when nothing is plugged in, but we need to know more about their design to know for certain.
K8MHZ
Senior Member
- Occupation
- Electrician
I have checked laptop power supplies and they draw zero when plugged in the 120 VAC recep, but not connected to the lap top.
K8MHZ
Senior Member
- Occupation
- Electrician
To know for certain, I will wire one up and test it. I will post the results.
There are little power eaters all over the place.
People arent going to shut the breaker, or switch, off to these things when they're not using them, no more than people would shut off the breaker to thier furnace, or oven,or receptacles that have alarm clocks plugged into them, or the doorbell transformer,or the TV, or the cordless telephone charger, or the plugin nightlite that seems to come on even in the daytime, or the Hot Tub sitting outsde, or the garage door opener,or the countless number of other things that consume electricity in our homes while we're not using them.
People arent going to shut the breaker, or switch, off to these things when they're not using them, no more than people would shut off the breaker to thier furnace, or oven,or receptacles that have alarm clocks plugged into them, or the doorbell transformer,or the TV, or the cordless telephone charger, or the plugin nightlite that seems to come on even in the daytime, or the Hot Tub sitting outsde, or the garage door opener,or the countless number of other things that consume electricity in our homes while we're not using them.
K8MHZ
Senior Member
- Occupation
- Electrician
That is correct.
If you know how to read a POCO meter to get watts (vs. watt hours) you can calculate the 'base load' for lack of a better term. Have everything not used turned off, but leave stuff plugged in. Then see how many watts are being drawn at that time. If the amount is negligible, obviously there isn't much to do from there....
Reading the mechanical meters required some info on the meter and some math. I used to have a 2/7 meter. You would use a stopwatch and time one rev of the disk and do math to find out the amount of watts.
The new digital ones are easier. They have a series of square blocks. One pattern cycle is one kW. Now you use a stopwatch and less math.
I used that method to find out that the small fluorescent light on my stove was costing me over 5 bucks a month to keep on all the time, which I did as it was used as a nightlight. Now I use LEDs for all my nightlights. Each one costs nine cents a YEAR to run.
I keep my desktop on 24/7 which costs about 7 bucks a month. My alternative would be to shut it down when I am not using it, which is an insufferable endeavor as it takes so long to boot back up. Plus, the only way to save a max of 7 bucks would be to not use it at all. When I want to look something up, I don't want to have to wait 10 minutes to do so if, for a couple bucks a week, I don't have to.
If your timing reveloutions of your electric meter with a stopwatch, youve got way too much time on your hands.
Must be an amateur radio operator thing.:happyno:
My 175 watt yardlight on the utility pole doesnt even cost me 5 bucks a month to run dusk to dawn, that flourescent on the stove must have been very inefficient.
Must be an amateur radio operator thing.:happyno:
My 175 watt yardlight on the utility pole doesnt even cost me 5 bucks a month to run dusk to dawn, that flourescent on the stove must have been very inefficient.
K8MHZ
Senior Member
- Occupation
- Electrician
If your timing reveloutions of your electric meter with a stopwatch, youve got way too much time on your hands.
Must be an amateur radio operator thing.:happyno:
My 175 watt yardlight on the utility pole doesnt even cost me 5 bucks a month to run dusk to dawn, that flourescent on the stove must have been very inefficient.
I took a solar PV class the summer before last. One section was on energy measurement, management and conservation. They had Kill a Watts there to take home if you signed them out. I thought they were cool and just bought one.
Between reading my base load and monitoring my individual loads I cut my electric bill almost in half. I am not being as scrutinous as I was at first, but my electric bills are between 45 and 75 bucks a month, and close to 10 of that is fixed costs in addition to usage.
I have a 175 watt sodium on a photo cell. That came to just about 5 bucks a month on average when I measured it.
Remember, the light on the stove was NEVER shut off. The outside light is on a photo cell. If you are looking at ways to reduce usage, the first targets are the ones that are on all the time.
There are 720 hours in a 30 day month. A 100 watt load on 24/7 would = 72 kWh per month. If you are paying 13 cents per kWh, that little 100 watt load will add $9.36 to the bill.
So, my 45 watt stove light cost $4.21 at 100 percent efficiency. It is an older one with an older ballast. I could see the extra 80 cents being due to age / inefficiencies. But most people, as you have indicated, really don't realize how much a light left on all the time, even a 50 watt one, can add to a month's electric bill.
The stopwatch I use is in my cell phone. Most people don't know they have stopwatches. They work pretty good, too.
kwired
Electron manager
- Location
- NE Nebraska
Don't forget the heat it is giving off. During heating season it is lessening the load of your heating system, during cooling season it is adding to the load of the cooling system.
If that's the case then the heat it puts out should be a non issue.
kwired
Electron manager
- Location
- NE Nebraska
Why? Didn't that equipment draw some energy if it gave up some heat?
My son is a computer tech, he has a huge desktop tower with a lot of high performance components including a graphics card with its own cooling fan. When he was still in college he would bring this thing home @ semester break and for the summers. The room it was in was always hot even when it had been sitting idle. There is definitely a significant amount of heat generated with some of this type of equipment. As I said - it will decrease heating system load, but will increase cooling system load. You still have a change in required energy even if heating system is not electric, it just will not show up on the electric bill.
Yes it did use energy and gave out some heat.
Since this heat helped reduce your heating cost in the winter time you gained a little.
Since it hindered your cooling system in the summer time then you lost a little.
Call that roughly an even trade.
So the burden is the cost of it using energy while its plugged in, not so much the heat it puts out.
Since this heat helped reduce your heating cost in the winter time you gained a little.
Since it hindered your cooling system in the summer time then you lost a little.
Call that roughly an even trade.
So the burden is the cost of it using energy while its plugged in, not so much the heat it puts out.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
It is roughly an even trade only if the energy cost per BTU delivered is the same for both your heating and your cooling.
If you use resistance heat and regular A/C, you will actually win. If you use heat pump and regular A/C you will break even.
If you use NG and regular A/C you will lose.
Not that the amount of power is all that significant either way, of course.
RustyShackleford
Senior Member
- Location
- NC
- Occupation
- electrical engineer
No. You gained nothing in the winter; that heat it put into your house, you paid for it with the electricity the thing used. In the summertime, you lost "a little" TWICE - the electricity the thing burned, plus the electricity the AC used to remove that heat.
This all assumes COP of both heating and cooling is unity. Of course, for cooling it always is higher, and for heating it usually is. If heating COP is greater than 1, you lose even in winter, since the device is electric resistance.
Of course, the amounts of energy involved are miniscule and it's remarkable that we're discussing it at all. But a similar analysis applies to water heaters in conditoned space, where the amount of energy is quite significant.
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kwired
Electron manager
- Location
- NE Nebraska
You are on the right track but is not all that simple. Remember even though the cost of electricity may be higher, if it was energy you were going to use anyway it did not add to the electric bill, it did lessen the heating bill, even if not much, but all the gadgets in a typical household all add up enough it may be more than you think.
During cooling season it does have a larger impact most of the time.
Don't forget the heat given off by lamps - especially incandescent or halogen but all lamps give up some heat, appliances, even non heating type appliances, refrigerators and freezers create somewhat significant amount of heat,
Some people have longer cooling season some have longer heating season others are about 50-50.
K8MHZ
Senior Member
- Occupation
- Electrician
I realized there was a sleep mode on my computer. It shuts everything off without having to re-boot when it's 'woke back up'.
I am now using sleep mode instead of running the computer 24/7. That should cut around 5 bucks off my electric bill.
I am now using sleep mode instead of running the computer 24/7. That should cut around 5 bucks off my electric bill.
RustyShackleford
Senior Member
- Location
- NC
- Occupation
- electrical engineer
Oh sure, I did not realize you were talking about energy you were going to use anyway. I thought the topic of this ridiculous
discussion was an always-on USB charger like in the nifty free sample from Pass&Seymour versus one you only plug in when you're using it.
K8MHZ
Senior Member
- Occupation
- Electrician
Oh sure, I did not realize you were talking about energy you were going to use anyway. I thought the topic of this ridiculous
I just tested my USB receptacle.
Connected to 120v, nothing in receptacle = 0.0 watts, and 0.0 volt amps.
When I plugged a hub with an led on it into it, the watts came up to 0.6, so I know it was working. When I unplugged the hub, the power went right back to zero.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Very interesting! So they either have a mechanical or electrical interlock in the receptacle (you tried plugging in a disconnected USB cable?) or they have an incredibly low power control circuit which turns off the power supply when there is no load for it, or the power supply itself has a very small no-load drain. (No input transformer for a start.)
K8MHZ
Senior Member
- Occupation
- Electrician
Good points. I did not try a disconnected cable, just the hub. I have taken the 120 vac cord off the receptacle so a quick check isn't feasible.
I have also measured laptop power supplies (not wall warts) that drew 0 when plugged into 120, but not not into the laptop. I think the likely reason is that the power control current is so low it can't be measured on my meter.
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