| Archive for Downsizer For an ethical approach to consumption |
| shadiya |
Energy consumption calculatorI daresay I'm being stupid but I need to know how to calculate how much power an electrical thing uses, going by whatever it says on the back, ie 400 watts or whatever. I'm pretty sure there is a link to something somewhere but my searches always end up with random results, battery chicken rehoming in this case??
Can someone help please? Thank you 
|
||||
| JB |
Watts (rated on back of device) x Hours in use = Wh
Watts (rated on back of device) x Hours in use / 1000 = KWh (which is what your bill will be measured in) And a few other useful conversions KWh x 0.53 = Kg CO2 (0.53 is the conversion rate for the UK, varies by country) kWh x 3 600 000 = energy in Joules Also it's worth noting that the rating on the back is often a peak load and will not be a true reflection of it's average power consumption. But if you're looking at lifetime consumption rather than usage it's also worth considering the manufacturing cost of the item which can be far higher than the energy that will be used to run it. (editted for typos (twice)) |
||||
| shadiya |
Thanks. I shall scribble it immediately on an envelope!
|
||||
| RichardW |
Is it? Even just taking electricity (cos gas & oil use can be calced in kwh) I thought it depended on how it was produced, transmission & efficencey losses (these are not static due to power made but not used). |
||||
| JB |
Yes it does depend on those. However power loss in long distance HV lines only accounts for about 1 - 2 %, variations due to inconsistent demand have surpiisingly little effect as the power companies are very good at predicting demand and can generally handle that without significant dumping of power.# The main factor depends purely on the way power is generated in a country. So in the UK we tend to use a lot of relatively efficient gas turbines and the conversion rate is 0.53, France is about 80% nuclear so their conversion rate is far lower, China uses lots of relatively dirty and inefficient coal fired stations so their conversion rate is far higher. Coal and gas can be expressed in KWh but as the original question was about electricty I ignored those. Also for practical purposes the CO2 impact of coal and gas can be calculated just by multiplying the fuel mass by about 3, rather than first converting to KWh and then back to mass of CO2. |
||||
| RichardW |
Ah cool.
I thought transmission losses were much higher than that. Sure I read some place that the losses were more like 30%. Maybe that was from the initial fuel used to the plug. Neat way to calc the other fuels Co2 too. |
||||
| JB |
Possibly but 30% still sounds very high for losses. Losses in the local low voltage transmission are relatively higher than the long distance but even so they are still dwarfed but the inefficiencies elsewhere in the system. i.e.why worry about 2 % transmission loss when your power station is only 50% efficient anyway and your customers are only 20% efficient at using power (no idea if those numbers are right but it illustrates the point)
Though of course one could argue then that you should modify that to calculate equivalent CO2. So all those dirty and inefficient systems that chuck out all kinds of incompletely burnt compounds might be even worse again. |
||||
| bodger |
My wife,is very much into gadgets and gizmos, now I'm sure that quite a few of us have them, but Kaz has bought a bit of equipment called an Owl. You clip it onto something or other where the power comes into the house and it gives you a digital read out of how much electricity is being used at any one time in the household.
She's really gotten into monitoring our energy consumption and I'm all for it, although its a bit off putting having to move through the house in the pitch dark.  At this moment in time, as the football pundits seem duty bound to say, the Owl says that we are using 0.274 units. The way it jumps up when you put the kettle or shower on, is almost frightening. The Owl is proving to be a very useful and informative bit of kit to have.
|
||||
| Shane |
One typo you missed - the above should read kWh / 3 600 000 = J, or Wh / 3 600 = J |
||||
| mochyn |
I'm tempted to get one, Bodge, but we use so little elec. to start with I'm not sure how useful it would be. How much are they? |
||||
| Rob R |
£25 to £35, depending where you buy
http://www.theowl.com/ |
||||
| mochyn |
Cheers for that me duck. | ||||
| Rob R |
I was going to get one but as we aren't using much electric it's pretty easy to just look at the meter & check appliances for their nominal consumption. Might get one when we get more buildings on grid. | ||||
| RichardW |
Some elec companies have given them away.
Also you might want a plug in meter so you can chase down what individual item is sucking all the power. |
||||
| JB |
I've played with owl type meters in the past but really want one that I could wire remotely into a computer and log consumption over time. So far haven't founf one, well I've got one but it only works with linux and I want other people to be able to use this. | ||||
| JB |
Used those and its more frightening to see not just what the power consumption is but what the power factor is. Some devices are not nearly as green as you think they are when you compare power consumption in watts and Volt Amps. |
||||
| RichardW |
Yes its bad how low some items PF is. At least you get billed for actual power used not PF corrected so you save a bit of money but the power company loose out as they have to make more than you use. I think businesses get charged for the PF as well so the devices that PF correct can lower business bills but not domestic ones (but still could be greener as they lower the need for power generation).
Its time that PF was also stated on the rating label. |
||||
| RichardW |
I am sure I was reading on the Navitron forum about a PC connection for an OWl type meter. |
||||
| JB |
Last I was looking lots of people had them listed as an option but nobody had actually made one. Either they were having technical problems making them work or they weren't convinced of the demand for them. The one I had worked under linux but windows insisted on caching the data and never updating it after the first reading. I could fix it but it's one of those things which was at the back of the list of things to do so I never got around to it. The other thing Iwanted was an owl type meter that I could plug in to any socket rather than having to clamp around just the live cable. There's lots of places where I wanted remote power monitoring but couldn't get into a cable to attach a monitor (customers worry when you start attacking their fuse box with a stanley knife )
|
||||
| Rob R |
Do you have any examples/prices for the plug in types? | ||||
| JB |
No. I found meters that could be read at the socket at that instant and which recorded a cumulative power figure but what I was after was something I could read remotely (like the owl stuff), into a PC (like very few items) and which didn't require a connection around just the live cable (which is what stuff like the owl units require and unless you want to just read the figure at the fuse box requires an electrician to install).
We did have some stuff designed for us which we could have extended to do what we wanted, albeit with relatively low accuracy, but that was custom designed for us and the quotes we were getting were too high to pursue at the time (it also did other stuff that we were interested in so the power reading was just an extra) |
||||
| RichardW |
£5 to £20
£5 from lidl when they have a special on & up to £20 from just about every where else (most in the £12-15 range). |