After replacing nearly all light in the house with CFL's and replacing
the old fridge with a class A one I was expecting to see a difference
in the monthly cost of leccy, but no!!
I have used 1344 units in 76 days according to the latest bill, so a
whopping 17.6kw a day !! now this seems a lot to me, house is heated
by oil, cooking by electric, three meals a day cooked, one was through
the washing machine and one tumble dry a day.
any one else done any studies on similar ?
18kW hours per day means you have an average consumption of 18/24 750W. If you have a couple of PCs left on 24 hours a day, that will
easily account for 200-300W. Add to that the fridge and a few lights,
and you can easily have a background consumption of say 400W. The rest
will come from your washing machine, dish washer, cooker and
(especially) tumble drier. Quite believable.
Couple of laptops on for 10 - 12 hours a day so you werent far off the
mark, but after about 11pm there's nothing on apart from the fridge
and freezer till 7am so there should be a BIG dip in demand there, I
still feel sommats not right ! complete long shot but have meters been
known to be out of calibration to an extent ?
I,ve ordered a plug in power meter to see whats drawing what, My
mother and father live up the road similar house and she has the
cooker on most of the day, with a monthly bill of £34 !! same company
Pick a couple of days, and take hourly meter readings, just to
see if you have a high background load, or if there's a large
load which comes on at a certain time. This might help narrow
down what's causing it. You could also try switching everything
off (not at the main switch, but at each appliance), and see if
the load drops to zero, or if there's something switched on
which you don't know about (e.g. the immersion heater).
I have a 2kW convector heater which is switched via X10. At
the end of the summer, I noticed it was on. I checked back
through my computer logs and saw the last X10 command I sent
it was an OFF, way back in February. Fortunately it was on a
thermostat, but even so, it had been coming on, probably during
the night, and eaten about £50 in electricity, comparing back
with previous years. I guess the X10 switch picked up a bit of
noise with caused it to come on (I've had this happen with X10
control of lighting during a power surge/dip). I have since
changed the computer programming to send a gratuitous X10 ON or
OFF command to it once a day to reinforce its intended state.
In another case, about 2 weeks after I moved in to a house, I
happened to notice the immersion heater was switched on in the
airing cupboard since the pervious people had moved out. Since
I was heating the cylinder with the boiler, this wasn't needed.
It didn't seem to burn up a noticable amount of energy though.
I have a Comfort alarm system, which includes Home Automation
capability. I don't use much X10 as mostly it is all hardwired.
I use X10 just for the ability to control portable appliances,
and where I want HA control of dimmable lighting. The HA
programming is split between the alarm system (for the parts
which can usefully run on battery during a power cut) and a
PC (for the parts which are useless without a mains supply,
such as the heating).
The alarm system provides all the inputs and outputs for both
alarm and HA functions (currently got 40 inputs and 40 outputs
installed; nearly all the inputs are used, but lots of spare
outputs). The alarm also sends and receives X10 commands.
The PC is connected to the alarm, and via that, picks up all
inputs, outputs, and X10 data received/transmitted. The PC
interfaces to the room thermostats through a combination of a
1-wire bus around the house supporting several DS18S20 digital
thermometers, and D/A inputs to read the position of the
temperature set dials on the room stats (which are actually
potentiometers). Software in the PC decides what temperature
each heating zone should be (e.g. use temperature setting on
room dial, or a preprogrammed temperature for unoccupied house,
night time, or frost protection as appropriate). The PC also
provides for remote access and off-site logging. I usually
switch my heating on as I leave the office.
My boiler is a Keston C25. This has an electrical input to
call for heat, and two outputs, burner on, and lockout.
These are all connected to the alarm, and via that, to the
PC. If the boiler does lockout, the PC will switch over to
use the 2kW convector heater instead, which it does by telling
the alarm to send the appropriate X10 command to the heater
switch, which I was referring to in the article you followed
up. When I originally installed the Keston 5 years ago, I was
working for Sun Microsystems and spent periods working in the
US. I was concerned that it might lockout and the house freeze
in my absence. Actually, it never did lockout until a few months
ago (due to drooping ignition electrode, a common failure
in Kestons it seems). The alarm phoned me to tell me the
boiler was locked out, which the lockout input on the alarm
had been programmed to do. As it happened, I was at home at
the time, but if I was out, it would have been useful to know
this had happened. Looking back through the system logs, I
could see that for a week before it locked-out, it had been
having trouble lighting, often lighting and immediately going
out, before staying alight on the second or third attempt.
I could program the alarm to alert me if it starts doing
this again, to forewarn of impending failure.
[email address is not usable -- followup in the newsgroup]
Essentially no laptops will ever use 100W.
60W is about the most, when charging, or 30W when in use.
Mine uses around 10W, but isn't very large.
The plug in power meters of the electronic sort can be significantly out
on modern power supplies of over 30W or so.
As in 100% out.
This may or may not be the case whith the one you have - the
three I bought from seperate vendors all suffered this.
The reason is that they are built to a price, and were designed without
regard to 'power factor correction' - which now has to be built into
power supplies of over 30W in the EU.
Turn off _all_ loads you know about.
Now, see if the meter still turns.
They measure power factor - this is fine and accurate for loads like
motors, fans, compressors.
The problem is that power supplies with power factor correction can draw
current in wierd spikes.
In one case I measured a very sharp rise-time pulse, like a sharks-fin.
The computer inside the meters is not fast enough to accurately read
this pulse, and makes bad assumptions.
I cannot comment on the maplin one - it might or might not work.
In any case, it'll likely be fine and accurate for most loads.
Just not some computers, and maybe large amps/hifi/electronics stuff.
No, they seem to sample the waveform, but not fast enough for some
The power supply I had would need a sample rate of around 1Khz for
It _seems_ to be more complex than simply assuming phase angle and a
sine wave, as it accurately gets 'simple' SMPSs and loads on dimmers
(as measured on oscilloscope)
The current Maplin one appears to get the measurement of PF
correct. I also have a Brennenstuhl one which Maplin used to
sell, and this appears to estimate the the phase shift (Ψ)
and apply cos Ψ to the VA to get the power, which goes badly
wrong with SMPSU's. Someone did say it works better with a
battery inside it, which mine doesn't have (it died).
I made a true power meter about 25 years ago which uses an
analogue multiplier, and doesn't suffer problems due to digital
sampling. It only gives the true power, and has no provision
for calculating VA or Ψ.
[email address is not usable -- followup in the newsgroup]
I have used average of 17.9 units per day over the last year - and
that includes washing machine, dryer, dish washer all on Economy 7.
I have PC on most of time, TV, usual domestic appliances, fridge, etc
Most lights CFL.
Not as formally as you. I've seriously reduced the number and length of
time the computers are on, fitted CFLs everywhere we can and tried to
reduce overall consumption by more concerted switching off.
Our bill for the quarter immediately passed fell about 2.5% compared
to the previous year. But ... electricity rose in price signficantly
over the same period.
Ignorance more frequently begets confidence than does knowledge: it is those
who know little, not those who know much, who so positively assert that this
I've been through the same exercise. You just have to get your power
metre plugged in and start measuring. In my case, the biggest unexpected
use was the two amplifiers that usually got left on and used by 100W
when not doing anything. I also had a couple of inefficient pond pumps
which have now been replaced. Other than that, the usage was down to
lots of fairly small things all adding up to a fair bit.
Interestingly, despite the government hype, the large CRT TV on standby
was using < 1W
Slightly different situation here; this is a 36 year old (two by four
wood framed) all electric house in eastern Canada. Any 'wasted' heat
therefore contributes, however slightly, to reducing electric heating
cost. This being a cool climate there is some heating most months of
the year; air conditioning of any type is rare (not needed) here.
Have not replaced light bulbs with CFLs due to high initial CFL cost
(e.g. around $2.50 Can, or approx one pound or more each) compared to
buying four regular incandescent cheapos for around 88 cents plus tax
= 25 cents (about 10-15 pence each). We replace about two packs (8
bulbs) besides any we break in the garage 'inspection light'.
Over the years we have installed four foot fluorescents (new fixture
about $25 = approx 12 to 15 quid?) in the kitchen and one other room
which tend to be on for long periods.
In the basement workshop have installed a long line of used
fluorescent which turned out to have 'electronic ballasts'. They are
on only while workshop is in use. With also occasionally use of a
bench saw, vertical drill press and and random use of an electronics
On the main floor, residentially, while each room has it's own
thermostat and individual heaters it is apparent that they come on
less in those rooms where there is otherwise 'wasted heat'. For
In the bathroom a row of six 40 watt bulbs above the vanity mirror
competes with the 500 watt baseboard heater; in the kitchen the
somewhat old (approx 20 years) and inefficient fridge if it wastes
heat, reduces the on time of baseboard electric there. In this room
two computers, printers modems etc, running continuously means that
baseboard heat rarely comes on even now with minus 4 Celsius outside.
One real cause of waste is however the tumble drier which shoves damp
warm air outside. Being an old (i.e. much used) fairly capacious North
American model it only runs for about 45 mins twice week. Clothes are
washed in cold or 'mixed' water. Just a few washes per week in a 20+
year old 'automatic washer'. Electric hot water is also wasteful
especially if it goes directly down the drain; although shower and
bath water can be allowed to cool to room temp. before pulling the
A single 'long life' 50 watt incandescent bulb which is on, (at this
time of year) for some 15 hours per night resides over the front door/
step to meet insurance/liability requirements. the nearest street lamp
being across the street and down the road a bit.
Total consumption, billed and paid monthly, averaged over a year is
around 2000 kilowatt hours per month. Including sales tax and a
monthly account charge the cost is presently $214 Can per month
(approx 110 quid?).
That's three to four times M.Helliwell's 18 kwatt.hrs per day; for an
all electric house in a colder, longer winter and more windy climate.
Ultimately this house will require more insulation, dependent on good
ventilation but avoiding rot etc.
Anyway just for comparison chaps (and the ladies)!
Yes, and came to the conclusion that it's a waste of time to fit CFLs
from the energy
The only worthwhile application I can see for them is in outside lights
which may be difficult to take
apart to replace them and where the poor colour rendition doesn't
matter too much.
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