How much electricity would I use...

[coffee]

Latest post of the previous page:

My 32 inches tv when standby would use <1w

[coffee]

I use the washing machine once a week for about 90 minutes but no stand by, but I have to leave the tv on standby just in case there is over the air software upgrade over night.

[Dave B]

Hello everyone,

I haven't got time to read all the responds yet so the following is what I think I understood please check to see if it is right.



"If you are talking "amount" then the 230 watts is that, the generating company will charge you by the number of Watts you use per unit of time, normally kW/h, thousands of Watts per hour, or, a 1000W electric fire left on for one hour uses 1kW/h!"

So if the tv power consumption is said to be 230w mean that the tv uses 230w per hour if left on? Which - Would it be written as 0.230kw/h?


***********************************


Actually I have checked again and my tv power consumption is actually 130 for a 32inches tv, which - Would it be written as 0.130kw/h?


I live in the Uk so UK mains voltage is 240V

P=VxA

A=P/V

A=130/240

0.542 Amp =130/240

Is the above working out correct? If so, What fuse would I use here Dave? A 3 amps fuse?


I have to go now, but I will come back later

Yes, coffee, the normal ratings are:
3 amp For appliances up to 700 watts
5 amp For appliances 701 to 1200 watts (1.2kW)*
13 amp For appliances 1.2kW to 3000 watts (3kW)

* Washing machines with even a 1000w rating may still need a 13A fuse.


The ratings below 1kW are rarely expressed as a fraction of a kW, so use 230 Watts rather than 0.23kW, as we would say the price of something is "25 pence" rather than "0.25 pounds" !)

[Griblet]

So if the tv power consumption is said to be 230w mean that the tv uses 230w per hour if left on? Which - Would it be written as 0.230kw/h?

I'm afraid that's not it. It's confusing, but leave out the "hour". The TV uses 230W, full stop. It would be correct but odd to write that as 0.23kW.
A watt / kilowatt is a unit of power-consumption. Only mention time if you want to work out the total energy used.

Concerning TV on standby: British Gas, for some reason, sent me a gadget which sits between the mains and the TV and is controlled by the TV remote. You set it to respond to the remote's ON/OFF button. Press ON once and the mains comes on, press it again within 10 seconds to turn the TV on. After that, another press turns the TV off, of course, then 6 seconds afterwards the widget automatically turns off the mains.
I wouldn't have bought such a thing but as it came free I use it. I find it rather good.

[Nick]

Doesn't that just move the standby function from the TV to the electric point? How does that save energy?

[Dave B]

Doesn't that just move the standby function from the TV to the electric point? How does that save energy?

I have wondered about that as well, after a friend raved about his "intelligent plugs" that switch the mains off if less than a certain current is drawn through them.. It may be that the switching device uses slightly less power, but that's still more than getting off one's arse to operate the mains switch. OK, some people hide the wall switch so well behind the kit one cannot get to it, also such "aids" are good for those who find it difficult to get out of the chair/bed.

All my kit is grouped on extension leads, one for the PC+printer+etc, one for the second monitor+powered speakers, one for the monitor/VHS player, one for the digital radio . . . but a separate one for the DVD player because the front panel switch on that only puts it on standby; then all of those plug into a 6 way switched ext. block. That way I have one "control panel" for powering up only those things I need at one time. Whole lot of electrical spaghetti though.

As a matter of interest (?) silly moment sums inform me that a single neon light consumes approx 50p worth of electricity per year

[Griblet]

Doesn't that just move the standby function from the TV to the electric point? How does that save energy?

Yes, it does draw a current but a very low one indeed. You're talking about milliwatts rather than tens of watts. A waste, yes, but IMO very convenient for an old person who's not too keen on getting out of a chair once settled.

EDIT: I must check those power-consumptions, though.

EDIT: Looks like I was wrong. I can find no figure for the 'standby saver' and in fact the TV is rated at only 1W on standby. Since I don't use the gadget to turn off my digital recorder as well, I may not be saving much.

[coffee]

Thank you everyone. Now that I have good idea how much electricity I am using, I can look for way to cut down the electricity bill where I can. If there is anything I need to know I will come back for more questions. Thanks again.

[Griblet]

Just don't ask about the cat in the box.

[coffee]

Hello again,

It about electric cooker, it have two small rings and two large rings, I am wondering how much electricity per ring would use for per hour please? I have searched the internet for information but I did not understand what they were saying so it would be great if someone here could explain it please. Thanks.

[coffee]

Hello again,

It is about electric cooker, it have two small rings and two large rings, I am wondering how much electricity it
using per ring per hour please? I have searched the internet for information but I did not understand what they were
saying so it would be great if someone here could explain it please. Thanks.

[robzed]

DISHWASHER

Assuming that hand washing is more better [more energy efficient / less water / lower carbon footprint / less detergent] than a dish washer - if you use your dishwasher correctly (aways use it full) might well be false.

http://www.treehugger.com/files/2005/08 ... r_vs_h.php
http://www.treehugger.com/files/2009/01 ... reener.php
http://environment.about.com/od/greenli ... ashers.htm
http://www.guardian.co.uk/money/2005/no ... almoney.g2
http://www.gizmag.com/dishwashers-save- ... ing/11410/

Google has hundreds of more articles.

TUMBLE DRYER
For those that live in a wet country, it's always been difficult. My mom did it be having lots of hanging clothes driers in the house. I need to have a think about the physics of this - you can't get something for nothing, so does evaporation come at an energy cost?

My tumble dryer is a condensing - no external outlet. This means that the waste heat goes to heat the house. I live in a terrace with lots of loft insulation, double glazing and cavity wall insulation.

From memory, gas is about 1/3 to 1/2 price of electricity for producing heat, so I'm probably wasting money, but I'm not convinced I'm wasting heat - because there are no radiators in the kitchen - it's heating by heat from the living room, cooker and tumble dryer. And we use the kitchen a lot - we are in there about 1/3 time when we are awake and in the house. (Occasionally we use a fan heater in the kitchen - especially when it drops to -15 C - burrr)

We only put the tumble dryer on if we awake and in the house.

OVERALL

Things are never clear.

I agree with others (Alan?) who said heating is the biggest cost by far. I'm not against turning things off when not in use (both to save energy, money AND safety reasons). But if you have decided to heat your house/office, then the best thing you can do is to turn down the heating a few degrees and wear a jumper!

[Dave B]

That is a poser, coffee, it may depend on the design of the cooker.

Some models have:

"fast" rings, high wattage for bringing things to the boil quickly and frying

and

"slow" rings - lower wattage for long simmering.

The two sizes are obviously to suit small and large pans.

Having checked on mine it seems that the two smaller rings are actually the same rating: 1200W and the large rings are 1800W at the front and 1500W at the back.

The type of ring is critical as well, mine has a ceramic hob and so heats up quite quickly. The ones with solid, cast iron rings take longer to heat and stay hot for longer after they are switched off, often wasting energy. Halogen hobs are even faster than ceramic!

I find that I can, for example, turn the ring under the pressure cooker of three or four minutes before the time, the residual heat keeps it hissing. Cast iron rings hold even more heat and can often be turned off up to five minutes before time when simmering.

If I have something in the pressure cooker and am going to fry a piece of chicken (say) I will start the cooker on the front large ring, move it to the back large ring (switched on at low) when it starts to hiss and then use the nice hot front ring to cook the chicken (or whatever) in a large frying pan!

Or it's the sauce simmering slowly on the back and the pasta bubbling merrily on the front!

Remember what I said about kettles, it applies here, it's better to get a lot of energy in fast if you are, say, bringing something to the boil. Long slow heating also means a longer time for energy to be lost from the ring or pan.

[robzed]

As a matter of interest (?) silly moment sums inform me that a single neon light consumes approx 50p worth of electricity per year

Care to give me the figures?

[robzed]

*Kettle small but still 2kW, low wattage kettles actually waste electricity; the extra time taken to heat the water also means proportionately more losses due to radiation & convection.

Yeah, I agree with this, and it might also be worth saying (I didn't see anyone else say) - only boil what you need immediately, i.e. a cup full or two - or the minimum fill level if that is higher. (I always refill to minimum since I have young children here - the kettle is out the way but they are at the height where putting it on would not be impossible. Also I'm stupid )

A friend of ours has a double-chambler kettle so he doesn't need to keep filling it up - only the outer chamber boils. A button press on the top moves water into the boiling chamber. Not sure if it's actually more efficient, but if refilling is a pain, then it saves the temptation to put more water in than actually necessary.

[Dave B]

*Kettle small but still 2kW, low wattage kettles actually waste electricity; the extra time taken to heat the water also means proportionately more losses due to radiation & convection.

Yeah, I agree with this, and it might also be worth saying (I didn't see anyone else say) - only boil what you need immediately, i.e. a cup full or two - or the minimum fill level if that is higher. (I always refill to minimum since I have young children here - the kettle is out the way but they are at the height where putting it on would not be impossible. Also I'm stupid )

Can't be bothered to go back now, Robzed, but if I did not mention that my kettle is safe with only a single cup of water in it I should have - I always measure one mugfull into the kettle for a single drink.

With ref to the neon lamp's consumption (I did it in me head last time):

The series resistor is usually 47 000 ohms, I am ignoring the resistance of the gas itself.

Power = V2/R (no reactive component) = 2402/47 000 = 1.2W(ish)

If the neon is on 24x365 that = 8760 hours

8760h x 0.0012kWh = 10kWh per year

At my new tariff of about 13p per unit that is, er, more than I got before, £1.30 per year!

Check my sums someone please!

[robzed]

= 1.2W(ish)

Your sums look ok (late at night) - but 1.2W ... you should able to feel that as hot...

[Alan H]

The resistor in series with a neon for 230 V would be more like 270k. Also, the neon voltage would be around 80 V, so the voltage across the resistor would be (230 - 80) = 150 V. This gives an rms current of 150/270000 = 0.56 mA. The resistor current is obviously the neon current as well, so the power taken from the mains is 230 * 0.55 mA = 0.13 W.

8760 hours per year gives 1.14 kWh, so at 13p per kWh gives about 15p per annum.

Does that look right?

[Alan H]

DISHWASHER

Assuming that hand washing is more better [more energy efficient / less water / lower carbon footprint / less detergent] than a dish washer - if you use your dishwasher correctly (aways use it full) might well be false.

Depends on whether you use a half-full setting - that may use less energy and less water, so difficult to call.

TUMBLE DRYER
For those that live in a wet country, it's always been difficult. My mom did it be having lots of hanging clothes driers in the house. I need to have a think about the physics of this - you can't get something for nothing, so does evaporation come at an energy cost?

Absolutely right - the heat to evaporate the water comes from whatever heat source you use to heat the house. If that is gas, then that might be cheaper that a tumble drier. In summer, it may be solar power!

My tumble dryer is a condensing - no external outlet. This means that the waste heat goes to heat the house. I live in a terrace with lots of loft insulation, double glazing and cavity wall insulation.

Good point - the heat on a vented one is wasted.

OVERALL

Things are never clear.

I agree with others (Alan?) who said heating is the biggest cost by far. I'm not against turning things off when not in use (both to save energy, money AND safety reasons). But if you have decided to heat your house/office, then the best thing you can do is to turn down the heating a few degrees and wear a jumper!

But it's not that simple! The heat generated by equipment on standby is dissipated into the room (so, if a device takes, say, 5 W, on standby, all of that 5 W will be dissipated into the room. If you have a thermostat on your central heating, it will switch on your CH less because of that 5 W and you will use less gas. However, the amount is tiny.

BTW, moving over to compact fluorescents light bulbs has the opposite effect: if you replace a 60 W incandescent bulb with an 11 W CFL, your Ch has to compensate for this by using 49 W more gas to keep the room at the same temperature.

This changes, of course, when you don't have any heating on - the heat generated by things on standby makes the rooms hotter and CFLs make it cooler than it would be with 'old' light bulbs.

To put things in perspective, a typical medium sized CH boiler (IIRC) is around 40,000 Btu, which generates 12 kWhr. So, when we're talking about an odd few watts here and there, it won't make much of a dent on your gas bill!

Just one more thing that some may not realise: all the electricity and all the gas you use heats the planet up. It is (essentially) all converted to heat that heats up the room, heats up the house and heats up the planet.

[Dave B]

The resistor in series with a neon for 230 V would be more like 270k. Also, the neon voltage would be around 80 V, so the voltage across the resistor would be (230 - 80) = 150 V. This gives an rms current of 150/270000 = 0.56 mA. The resistor current is obviously the neon current as well, so the power taken from the mains is 230 * 0.55 mA = 0.13 W.

8760 hours per year gives 1.14 kWh, so at 13p per kWh gives about 15p per annum.

Does that look right?

270k not 47k? Ah, there goes my memory again! Well, only ten times out on the current . . . .

I'll keep quiet in future.

[coffee]

Thank you everyone.