What uses most power?

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What uses most power?

Postby zzsstt » Fri Apr 15, 2011 1:32 pm

A post on this forum, together with a conversation I recently had with a friend, lead me to contemplate where the majority of an electricity bill actually comes from. The statement was made that the making of toast would need to banned because of the cost of electricity was increasing.

Some brief calculations suggested that a 2kw toaster, taking perhaps 2 minutes to brown a couple of pieces of toast, used about 2/60 X 2 = 0.07kwh, which would cost perhaps 1.5c at current prices.

On the other hand, the background use in a typical household could easily be 400W to 600W. Many homes with inefficient fridges/freezers, multiple older items with poor "standby" performance, or luxuries such as waterbeds could be using far more. Compared to the 1.5c for toast, a 500W background use equates to .5 X 24 = 12kwh/day, or upwards of $2.80.

So perhaps the quest to save power on expensive items that do useful work (washing machines etc.) and also have high embedded costs, should become far less publicised whilst the background usage 24/7 use should be the major target? After all, switching the TV off at the plug does not cost anything, but may well contribute more to the electricity bill than the time over which it is actually switched on!

Whilst none of this is new, it does once again seem to me that the push to sell a new product outweighs the far more "environmentally friendly" solution of keeping the existing product but using it in the most efficient way........
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Re: What uses most power?

Postby lantern » Fri Apr 15, 2011 2:33 pm

A good friend of mine wires up solar systems in Brisbane.
One job he told me about was one where, when everything was turned off ,there was still 1kW of load, 24/7
from appliences being on standby.

Very costly!
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Re: What uses most power?

Postby Gordon-Loomberah » Fri Apr 15, 2011 6:50 pm

lantern wrote:...when everything was turned off ,there was still 1kW of load, 24/7
from appliences being on standby.


:? hmm, say 25W/appliance, that would be 40 appliances, or say an excessive 40W each would still be 25 appliances!
Thats a whole lotta appliances ... methinks there's a fridge or 2 running hidden in there somewhere.
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Re: What uses most power?

Postby Alex Morrow » Fri Apr 15, 2011 10:05 pm

What zzsstt reports seems to make sense to me. During the day, reading the inverter and the little meter that the state government sold me for $50, my household usage averages around 400 W at any given time. That means 9.6 kWh in a day. According to my (perhaps faulty) maths, taking the monthly import, adding what the inverter says it has produced, and subtracting the monthly export, I am using around 11.5 to 12 kWh a day. That seems to indicate that only around 2 kWh is being used for the kettle, cooking, lights at night, water pump, and so on. (I only turn on the hot water booster if there hasn't been enough heat in the day.) Perhaps not much scope for reducing that, but there must be plenty of scope for reducing the "standby" usage.

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Re: What uses most power?

Postby bpratt » Fri Apr 15, 2011 10:06 pm

Perhaps the neighbour has a hidden extension running over to their house ??

Have heard it isn't all that uncommon.
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Re: What uses most power?

Postby sandystone » Sat Apr 16, 2011 11:22 am

A KW on constantly....?
I have seen houses with 20 - 30 appliances with standby, and or power supply transformers all chugging away constantly, so this seems possible, but perhaps not all that common.
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Re: What uses most power?

Postby karlajensen » Sat Apr 16, 2011 12:44 pm

Fridges run compressors on and off, I have yet to see an inverter drive fridge but can be sure it isnt far away
or out there already.hard

A 400+L fridge will use 150W get a couple of those a bar fridge a wine fridge a beer fridge
all of a sudden spinning the meter pretty

I can get my standby down to about 100W but that seems to be it

a few smart switches here and there and perform well and my
"always on" useage has decreased as I implement these systems
from 50KW/week down to the 35KW/hrs a week I'm at now.

this is a saving of ~780KW / year or $170.

thus it does add up, spend $100 on a monitor and $100 on a couple of self disconnecting powerboards
a new TV and you're on the way.
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Re: What uses most power?

Postby lantern » Mon Apr 18, 2011 11:19 am

hmm, say 25W/appliance, that would be 40 appliances, or say an excessive 40W each would still be 25 appliances!
Thats a whole lotta appliances ... methinks there's a fridge or 2 running hidden in there somewhere.


Belive me, I saw pics of the install the house was massive, the owner had much more money than sense.
The installer has been installing for well over 20 years, fully qualified sparky as well. He knows his stuff.
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Re: What uses most power?

Postby zzsstt » Wed Apr 20, 2011 8:31 pm

Gordon-Loomberah wrote: hmm, say 25W/appliance, that would be 40 appliances, or say an excessive 40W each would still be 25 appliances!
Thats a whole lotta appliances ... methinks there's a fridge or 2 running hidden in there somewhere.


A ducted air conditioner, plus a couple of splits, even on standby can soak 200W+ constantly. Add in all the computer and comms gear, a couple of Foxtel/Austar boxes, some hifi gear on standby, two or three TV's, DVD players, PVRs etc. Then add the myriad of other "constantly on" devices, clocks on ovens, alarm clocks, dishwashers, washing machines etc. each of which may only draw a few watts, but it all adds up.

I once connected all the computer gear on my desk through a PowerMate and was astounded at the result. Nothing actually switches off (or didn't until I added a global foot switch!), so whilst most devices only draw a few watts:

PC
monitor
amplified speakers
internet modem
network switch
laser printer
label printer
scanner
USB hub
backup eSATA drive
UPS

It's not hard for a typical computer setup to suck >100W even when "slept".

So, 200W for aircon, 100W for a computer and we're a third of the way to 1kW without trying very hard! Give the kids a computer or two, plus a Playstation? I wouldn't be surprised if the average house uses >700W continuously. In fact, if you think that the average household consumption is about 17kwh per day, where does it come from? At 0.035kwh per slice, it's a lot of toast!
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Re: What uses most power?

Postby munrre » Thu Apr 28, 2011 11:26 am

Yes, I tested our UPS and they do draw a lot of power. Needless to say it is no longer in use.
The only thing we have on standby now is the Set top box/PVR.

I switch the reverse cycle AC standby off at the meter. However, be aware that some of these need to be "warmed up" for a few hours before use.

Our all electric house for 3 is currently (Autumn) using between 6 and 8 Kwh per day.
I'm pretty sure most of that is the fairly new fridge and ludicrously large LCD TV :oops:
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