Even
though your gas meter records your gas consumption in hundreds of cubic feet,
your energy company is required to bill you
in terms of kilowatt hours (kWh).
This seems to be an uneccessary complication, that is, until you need to consider
how you might
compare your gas charges with your electricity charges (which
have always been billed in kWh). A Kilowatt-hour is an amount
of energy equal
to 1 killowatt (1000 Watts) operating for 1 hour. So when you consider an electric
fire that will consume, say, 2 Killowatts
in an hour, against a gas fire that
may consume 1.5 kilowatts an hour you can see which has the lowest running cost
by looking at what
you pay for a kWh of gas and a kWh of electricity where
you live.
This is not to say that gas fires are cheaper to run.
What
is the calorific value of gas, where does that come into it! and why does it vary?
The calorific value is a measure of the heat contained in the gas, it represents
how quickly the gas can heat up water to a formula which is
applied to the
gas when it is tested periodically at various points throughout the national grid
system. In simple terms gas delivered to homes
near the point where it comes
ashore contains a different level of moisture than the gas which is used say 50
miles from the shore.
Moisture in the gas affects it's performance and so
the calorific value element should ensure that a hundred cubic feet of gas used
inland, costs
the same to the consumer as a hundred cubic feet of gas consumed
on the coast - for doing the same amount of work.
So how do we convert hundreds of cubic feet of gas to kilowatt-hours?
For this example take the current reading of your gas meter and deduct the previous
meter reading from it. If your previous figure was an
estimate this estimated
reading may actually be higher, in which case deduct the previous reading from
the current reading. This does not affect
the arithmetic it just means either
you have more to pay, or your energy company owes you something back.
Either
way the difference between the numbers is net hundreds cubic feet of gas.
Take this result and multiply it by 2.83, this converts hundreds
of cubic feet to cubic metres.
Multiply this result by a correction
factor of 1.022640 and then by the calorific value shown on your
last
gas bill. Finally divide the result by 3.6 to give kWh.
As
a very rough check a hundred cubic foot of gas is beween 28 and 31 kWh depending
upon the conversion factors which are used.
Obviously the consumer has no
option but to rely upon the accuracy of the suppliers declared calorific value
and conversion factors.
We have no evidence to suggest that there are any
irregularities, but this is perhaps an area which one hopes is tightly monitored
by the
regulator Ofgem, and the consumer body Consumer Focus, simply because
it is subject to some variation between geographical areas.
Paying
Too Much? - use an impartial online price comparison tool. The results are displayed
in a table to make comparisons easy.
Switching data is updated
regularly and can give you a comprehensive guide to the suppliers prices for your
area.,
you the Consumer has the power to choose on a variety of utilities
and financial products.
Hundreds
Cubic Feet to Cubic Metres
A Cubic foot is (12 X 12 X 12)
1728 cubic inches, therefore a hundred cubic feet equal 172,800 cubic inches.
A
Metre is 39.375 inches, therefore, a cubic metre is (39.375 X 39.375 X 39.375)
61046.629 cubic inches.
Divide 172,800 by 61,046.629 and you get 2.83 to three
decimal places.
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Correction factor- Natural mains gas expands
and contracts depending on its temperature and the pressure it is subjected to.
So the amount of energy contained in a cubic meter of gas is worked out using
a standard temperature of 15o C and a pressure of 1013.25 millibars. However,
the temperature and pressure at a British meter is, on average, slightly different.
To correct the figures for the difference, they have to be multiplied by 1.02264.
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