Natural Gas Pricing

In the UK we are charged by the kWhr or units used, very similar to the electricity..

The gas meter is a volumetric measuring device so it has to be corrected for pressure in the pipeline, about 2%, and then the average calorific value of the gas is used to convert the corrected volume used into kWhrs of gas used. this is then charged per kWhr (or unit).

John.

Thankyou for your reply

Fine, however, even if the fluctuations in pressure occur how do we know as consumers that the flow meters are accurate or that the fluctuations are correctly calculated, or are they an estimate - how do we know that the variance is 2%? I have no way of telling? but it would be good to understand fully these procedures which is why I posed the questions.

What is the norm/standard for such a volumetric measuring device. Presumably they are manufactured to a British standard and if so what are the parameters governing their performance?

Do increases in the content of other gases within the methane mix such as formaldehyde and other carbon gases and acids influence the combustability of the gas irrespective of the averaged calorific value?

Who sets the safe levels for these many other gases and in particular formaldehyde?

As standards and acceptable levels of other gases must be regulated, how are they measured?

Lots of questions and probably answers available somewhere.

Many thanks

Ahhhh now that is my area of expertise, gas flow measurements....

The flowmeters are remarkably accurate as they work on positive displacement principle... they also have an excellent turndown ratio, from measuring the gas used for a single pilot light to a 30 kW gas flow.....

Up to 10 years ago they never bothered to allow for gas pressure, so their prices reflected this, and then someone official said they must show the true value.... this the gas companies did by increasing the amount of indicated gas used, but the price stayed the same of course....!

How do we know the variance is 2%? Well using Charles or Boyles ideal gas laws and a change of pressure of about 25 mbar gives this correction figure.

The calorific value for the gas used is calculated as an average from a large gas field (Bacton Gas) and will vary depending on the constituents of the gas - But that is a laboratory calculated figure which is independent of the commercial suppliers.

I should add that the gas composition is very closely monitored, as any unusual build up could be extremely dangerous... especially of moisture.

As for your other questions about who sets standards and monitors the properties of the gas supplied is by an independent laboratory set up and run by the government.

John.

Dear John

Many thanks. I still wonder why the energy companies are not more transparent with their data and their lifeblood - namely You and Me.

So we end up back at the government for lab tests and remainder gas analysis. I shall make enquiries

Thanks again

Jonathan

I've always had a nagging suspicion about natural gas suppliers. How do I know that I'm getting what I pay for? I know that the meter accurately measures the volume I consume but what about the calorific value? The pipeline suppliers tell me that they have to adhere to minimum standards of around 1000 btu's/cu.ft. but how can I check that? I can easily check the voltage of the incoming electricity to my house and if it is lowered substantially, things around the house start to malfunction in an obvious way. But I can't tell from looking at my furnace or gas range if I'm not getting full value for my natural gas. Anybody else thought about this?

Anyone know where I can find a price history graph for natural gas for the major regions of the world, preferably a 20-30 yr look, and ideally forecasting out to 2010? Thank you for your help!

Hmmmmm I could add that how do you know you are getting the correct value for electricity?

Measuring the supply with a voltmeter is the same as measuring the gas supply with a pressure gauge, it doesn't tell you of the energy available for you to use....

In the UK we have 240 Volts... but measuring this doesn't mean I'm going to get 1kWatt out of my electric fire...

The power measurement is made by a wheel spinning in a magnetic field.... How accurate is that?

What if you had a perfect inductor across the mains, it would dissipate nothing, so no power used, but it would take current, would the household electicity meter still read zero power used?

I've never tried it to find out, mainly because I don't have a perfect inductor etc....

With the gas supply I suppose we have a similar problem.... I know that the gas appliance manufacturers have a final test fo gas burners / hobs etc... and that relies on the eye watching the shape and colour of the flame to ensure the correct mixture of air and gas is being burned - Their supply of gas is from a cylinder of known quality gas....

The colour of the flame is a remarkably accurate way to evaluate correct combustion and also the gas characteristics....

I suppose in the end as consumers we have to rely on Government departments to keep an eye on suppliers to make sure that we are not being mislead.....

John.

From what I remember from university days the answer to having a perfect inductor across the mains would not cost you anything as the meter uses vectors to produce the reading rather than scalar values. In other words if you don't use any power you don't get charged. That's one of the reasons they get upset with unbalanced loads.

One thing I have noticed is the number of posts that mix measurement standards like BTU/Hour and Calories along with Watts and Jules. Life is so much easier if you stick to SI units.

Trouble is the gas companies don't charge in SI units (joule for energy) and there'd be a lot of them in the average gas bill - 3600000 per kWh.

To answer the question that started all this, a therm is defined as 100000 BTU, so it doesn't vary. In the old days (in Britain) gas was sold by the 100 cu.ft so with a typical calorific value 1000 BTU/cu.ft it worked out neatly at 1 therm per 100 cu.ft.

Re electric meters - as you say they are designed to take account of power factor so you only pay for energy used. In theory it should read zero on a perfect inductor (or capacitor) but I don't know whether it would, though in practice it doesn't see this situation. Also for industrial users the kVA is also taken into account as the various conductors have to be rated for the current drawn even if a low power factor reduces the kWh figure.

Hi Codemaster, thanks for the info on the therm.... I was planning on digging out my old books on the Btu units of measurement, I've used SI units for so long now....

As for the electricity meter, I am not sure whether the measuring principle of the household meter would take in to account phase angle, lead or lag....?

Someone must know? If not I'm off to dig out some old reference books....

I'm not sure that you are right though about the household meter not seeing this power factor though.... fluorescent lighting is certainly highly inductive..... although heating appliances will be almost purely resistive.

Interesting I must find out..... John.

I said it does take account of power factor, and I'm fairly sure that's correct, though I don't know just how it does it. It wouldn't (or at least shouldn't) matter whether PF was lagging or leading as cos x is an even function (cos x = cos [-x]). If you measured the amps on a fluorescent lamp I think it would read higher than power/voltage.

I'm sure you can get a kVAh meter if you want, probably easier to design than kWh meter.

Cheers

Older KWH meters use a voltage coil and a current coil and are designed to measure power rather than VA. The end result is if power factor falls below 0.5 they run backwards. Some older 415v welders were good at sending one meter backwards for this reason when they were idling.

Modern electronic meters record power factor and poor power factor is expensive for industrial users.

Mine dose. The units for pricing re MJ (Mega Joules). And as to their being a lot of them that's why the metric system has multipliers remember this.

Terra = 1,000,000,000,000 = 10¹² = T

Giga = 1,000,000,000 = 10⁹ = G

Mega = 1,000,000 = 10⁶ = M

Kilo = 1,000 = 10³ = K

Mili = 0,001 = 10-³ = m

Micro = 0,000,001 = 10^-6 = μ

Nano = 0.000,000,001 = 10^-9 = n

Pico = 0.000,000,000,001 = 10^-12 = ρ

And that covers almost everything yow will ever need to measure.

Hi, just numbers and there are a lot more to recon with - read Tesla. But how do you know that your energy bill is accurat and if it is accurate according to someone using lots of numbers, what exactly are you charged for within all those numbers - it is still not clear on my energy bill -----yet

The easiest way to understand your energy bills it to convert all of them to a standard unit of measure and in the metric system the unit for energy is a Joule which is the amount of energy that is produced when you supply 1 Watt of power for 1 second.

So for you electricity bill 1KWh means you have used 1,000 Watts for 1 hour or 3,600 seconds. Therefore

1 KWh = 3,600,000 Joules = 3.6MJ

Now a Therm = 100,000 BTU (British Thermal Units) and 1 BTU = 1,054.8 Joules Therefore

1 Therm = 105,480,000 = 105.48 MJ

So if you convert everything to joules you can compare apples with apples.

I hope that will help.

Many thanks for that. It is helpful. I guess the questions would never have arisen in the first place of things were better explained by the energy corporations. It still appears that there are some anomolies that could be improved along with some improved communications with the consumer. Ah well.

I was referring to basic SI units like watt and joule, as mentioned in your post, not multiples of these. As a matter of interest, is electric in Oz also charged in MJ?

PS it should be tera and milli.

Nu unfortunatly its charged in KWh but its an easy conversion.

A therm is defined as 100,000 Btus. Gas meters measure volume. 100 cu-ft of gas at a standard pressure and temperature is approximately 1 therm. Pressure before the meter is normally regulated with a pressure reducing valve. Temperature may or may not be measured and compensated for at the meter.

The variance between CCF and therm measurement is dependent on the make-up of natural gas as well as pressure and temperature. It is not 100% methane, but includes small amounts of other combustible gases like propane and even non-combustable gases like nitrogen. When the customer is billed in therms, the gas company is measuring the btu content of the natural gas per unit of volume, averaging over the period of the bill and then applying a compensation factor to the customers bill.

ummmm. So my bill is an approimate average of a product I buy?

Well dig-deep, I guess its better than being an approximation of an average estimate!!?

John

Nice one!! & Thanks - I only asked.

Anyone know where I can find a price history graph for natural gas for the major regions of the world, preferably a 20-30 yr look, and ideally forecasting out to 2010? Thank you for your help!

http://www.aga.org/Template.cfm?Section=AGA_News1&template=/ContentManagement/ContentDisplay.cfm&ContentID=21004

This will give some info

Rustyh2o

Thanks! Do you know if price increases for Nat Gas in US have been similar in Europe and Japan?