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Combi boiler gas consumption |
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| message from Paper2002AD on 16 May 2004 |
in December and January I was decorating an otherwise empty house, and I had
the central heating running on its lowest setting, sometimes for 8 hrs a day,
sometimes just on and off for 2 hrs morning and 2 hrs afternoon. Consumption
averaged 5.1 KWH per day.
The house has been occupied since early Feb, and the occupant has been using
CH, a gas room heater, and a washing machine. Consumption has averaged 12 KWH
per day.
Seems flipping high to me!
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| Andy P replied to Paper2002AD on 18 May 2004 |
I wish mine was that low! My 3 bed solid wall semi averages 85kWh per
day. Just to be certain, you do mean kWh and not "units" don't you? If
it's "units" then it seems a bit high, if kWh I would think that 12 per
day is good.
I guess an important consideration is how hot the occupant likes it. I
work from home a lot so in the winter the whole house is heated most of
the day. If the occupant does similar then looking at the maths:
You averaged 5.1kWh per day based on 4 or 8 hours use per day. This
works out at an average of 0.85kWh per hour. The occupant is possibly
heating the house from say 7am to 10pm (maybe even longer) so will be
using 12.75kWh per day.
Now its getting warmer then the gas consumption will go down. Between
June and September last year the gas consumption was close to zero. Too
many take aways and NOT enough home cooking;-)
Andy
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| Paper2002AD replied to Andy P on 18 May 2004 |
Bugger! That was 12 units a day, not KWH - sorry to everyone who's replied to
my false premise!
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| IMM replied to Andy P on 18 May 2004 |
POWER
The watt (W) is a unit of Power.
The kilowatt (kW) is simply 1,000 watts. A one-bar 1 kilowatt electric fire
or ten 100 watt light bulbs will consume one kilowatt.
BTU/hr is a unit of POWER
ENERGY
Energy is Power x Time.
You pay for energy not power. What you have to pay for is the product of
power and time. This is obvious - the electric fire operating for three
hours is going to cost three times a much as for one hour. Therefore the
chargeable electricity 'unit' is the:
kilowatt-hour (kWh)
This is by tradition in the world of electricity metering just called a
'unit'. What you are paying for is energy, rather than power.
kWh is energy
Wh is energy
In days gone by, boilers etc. were rated in British thermal units (BTU or
formerly BThU) per hour (BThU/hr), which is POWER.
The BTU is a unit of ENERGY
The BTU is not power. Hence the division by time to get back to power.
People often speak of say, a "60,000 BTU boiler" - when what they really
mean is 60,000 BTU/hr.
One kWh (ENERGY) is equivalent to 3,412 BTU (ENERGY)
Note: One figure has a time factor and one does not.
A 60,000 BTU/hr (POWER) boiler is rated at approx 17.6 kW (POWER).
Note: The time factor figures are reversed for power.
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| Andy P replied to IMM on 19 May 2004 |
But NOT gas. Domestic gas meters measure the volume of gas used. So one
gas unit is not, as it is in the world of electricity metering, one kWh.
As I've just realized, not all gas units are the same. It seems that
modern meters measure cubic metres directly so one unit equals one cubic
metre. On my meter one unit equals 0.353 cubic metres. You then still
have to do all the maths to work out how many kWh you are being charged
for.
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| IMM replied to Andy P on 19 May 2004 |
Gas nowadays in the UK is charged in kWh (ENERGY), just like electricity.
There is a difference though in that the electricity meter measures kWh
directly, whereas the gas meter records the volume of gas used in multiples
of 100 cubic feet (or in cubic metres on newer gas meters). The calculation
to get from volume to energy in kWh (ENERGY) is shown on the gas bill. The
conversion factor is not constant since it involves the calorific value of
the fuel, which varies from region to region.
Therm
In the past, gas was charged for by an energy unit called the Therm. One
therm is simply 100,000 BTU (ENERGY), equivalent therefore to 29.31 kWh
(ENERGY).
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| derek replied to Paper2002AD on 17 May 2004 |
It's only the equivalent of a single one bar fire on 12 hours to heat
the whole house and heat the hot water.
The period began in February.
We'd need to know a lot more about the house to give a better answer
but I'd say it's in the right ball park. Quite good even.
DG
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| Paper2002AD replied to derek on 17 May 2004 |
It's a two up two down terraced, with a Gloworm boiler. That rate of
consumption is significantly more than my own four bed detatched with an Ideal
compact boiler
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| Andy Hall replied to Paper2002AD on 17 May 2004 |
It could be if the house has solid brick walls with no insulation in
them. The U value is a great deal more than for even a cavity
wall.
If it's an older Glow Worm crappy boiler, then it is unlikely to be
more than about 60% efficient.
.andy
To email, substitute .nospam with .gl
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| BillV replied to Andy Hall on 18 May 2004 |
The other unmentioned factor is that "gas room heater", I wonder what that
is; could be some looks-nice-but wildy inefficient beast.
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| The Natural Philosopher replied to Paper2002AD on 17 May 2004 |
The energy report on my house told me that the boiler had to have at
leats 10kW to keep it warm at -5C. Assuming 20C internal temp.
That's a brand new to full insulation spec house - large, but well
insulated.
Asssuming an average winter temp of say 5C, it looks like about 6KW is
needed CONTINOUSLY to heat it - say 144kWh per day.
I was burnbing something like 1000 liters of oil a month in the coldest
month - what's that ? 180 quid a month? 6 quid a day at about 3p per
Kw/h? 20Kwh per day?
Sounds totally ressonable and very very good to me, to get 12Kwh per day
That is an average power level of only 500W. or ten might bulbs.
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