I changed my dual fuel tariff with EON recently. New one is fixed until
next October. With my new deal came a "Energy saving monitor" - it tells me
how much electricity I'm using.

I've checked the readings of the monitor against my meter readings. The
monitor tells me I'm using approx. 15% less than my meter readings.

Are these monitors that inaccurate ? Or could my meter be over reading my
usage ?

Any thoughts ?

TIA

"Hugh Jampton" <me> wrote in message
news:edlg
> I changed my dual fuel tariff with EON recently. New one is fixed until
> next October. With my new deal came a "Energy saving monitor" - it tells
me
> how much electricity I'm using.
>
> I've checked the readings of the monitor against my meter readings. The
> monitor tells me I'm using approx. 15% less than my meter readings.
>
> Are these monitors that inaccurate ? Or could my meter be over reading my
> usage ?
>
> Any thoughts ?
>Have a look at the makers website for the meter, and it should tell you how
accurate their meters are. Some of them, the cheaper ones, have an accuracy
of around 15 to 20 per cent Plus / Minus the full scale of the reading. So
it sounds like your energy meter is about right for a cheap one.

On Tue, 11 Nov 2008 21:17:23 +0000, Hugh Jampton <me>
wrote:

>I changed my dual fuel tariff with EON recently. New one is fixed until
>next October. With my new deal came a "Energy saving monitor" - it tells me
>how much electricity I'm using.
>
>I've checked the readings of the monitor against my meter readings. The
>monitor tells me I'm using approx. 15% less than my meter readings.
>
>Are these monitors that inaccurate ? Or could my meter be over reading my
>usage ?

The "whole house" monitors which clip over one of the feeds to the
electricity meter and have a remote reader are really quite
inaccurate, vastly more so than the meter. They are mainly greenwash
where being seen to be doing something is considerably more important
than actually achieving something.

The ones you plug into a socket and then plug the device into them are
quite accurate even when the load is "difficult" (such as switched
mode power supplies).

In article <h91kh4hfm7pob07e5lkgji5u476cant9vv>,
Peter Parry <peter> writes:
> On Tue, 11 Nov 2008 21:17:23 +0000, Hugh Jampton <me>
> wrote:
>> The "whole house" monitors which clip over one of the feeds to the
> electricity meter and have a remote reader are really quite
> inaccurate, vastly more so than the meter. They are mainly greenwash
> where being seen to be doing something is considerably more important
> than actually achieving something.

They can't measure power at all -- the reading is a guess.
They can only measure current, and then have to guess the
voltage and phase angle to estimate the power.

Peter Parry <peter> wrote:
> The "whole house" monitors which clip over one of the feeds to the
> electricity meter and have a remote reader are really quite
> inaccurate, vastly more so than the meter.

Inaccurate in what sense? I can see that a monitor that
returns significantly different results at different times
for the _same_ power usage would be useless; but one that
was always (e.g.) reading 20% high would still be useful as
a guide to whether your power usage had gone up or down.


#Paul

On 11 Nov 2008 23:40:59 GMT, andrew (Andrew
Gabriel) wrote:

>In article <h91kh4hfm7pob07e5lkgji5u476cant9vv>,
> Peter Parry <peter> writes:
>
>They can't measure power at all -- the reading is a guess.
>They can only measure current, and then have to guess the
>voltage and phase angle to estimate the power.
>

Part of the set up for the electrisave allows you to set the mains
voltage from 220v to 250v in 10v increments. If you know the voltage
and it is reasonably constant this type, at least should be reasonably
accurate if the power factor is cloes to 1.

They're perfectly reasonable devices that give a rough guide to
consumption without having to log meter readings all the time. They
can also remind you if you've left 300w of light on in that room that
you only go into once a month!

On Wed, 12 Nov 2008 08:22:26 +0000, kinslerp
wrote:

>Inaccurate in what sense? I can see that a monitor that
>returns significantly different results at different times
>for the _same_ power usage would be useless; but one that
>was always (e.g.) reading 20% high would still be useful as
>a guide to whether your power usage had gone up or down.

As Andrew has said they simply measure current. They cannot factor in
voltage or phase angle. As a result the readings can vary quite a bit
while the load remains relatively steady or can remain steady while
the load varies. They can also be very misleading on certain loads
with power factors which are not unity such as electronic devices
using switch mode power supplies, motors and some fluorescent lamps.

While some allow manual alteration of the mains voltage away from the
preset value none cope with the daily cyclical variations of 10-20V
which occur in most locations. The result is a device whose readings
can vary inconsistently by an amount greater than the variations a
user may make with small changes in energy use.

They will certainly show you that switching an immersion heater on
makes a big difference to consumption, they won't reliably show a
saving switching all your electronic devices off rather than leaving
them in standby will make as the measurement error will exceed the
measurement itself and will produce overly optimistic measurements as
such loads often have low power factors.

Not only can they show significantly different results at different
times for the same load they can also show significantly different
results for two loads taking the same power but with different power
factors. Overall their accuracy is in the order of plus/minus 10%
either way but it can exceed that on individual measurements.

Most manufacturers say their purpose is for "behaviour modification"
rather than measurement. Whether the "modification" is worthwhile
doesn't seem to be considered to be particularly important.

Thank you all for the replies.

It looks like my monitor is not as accurate as I thought it would be -
guess I'll get used to it and make adjustments.

BTW - I have no idea who the manufacturer is - it just says EON on the
monitor.

Thanks again.

"Hugh Jampton" <me> wrote in message
news:ddlg
> Thank you all for the replies.
>
> It looks like my monitor is not as accurate as I thought it would be -
> guess I'll get used to it and make adjustments.
>
> BTW - I have no idea who the manufacturer is - it just says EON on the
> monitor.
>

>

its not this one is it?
http://www.currentcost.com/index.html

On Thu, 13 Nov 2008 15:18:11 -0000, Paul wrote:

> its not this one is it?
> [..]

That's the one !

Interesting site - thanks.

Peter Parry wrote:

> Most manufacturers say their purpose is for "behaviour modification"
> rather than measurement. Whether the "modification" is worthwhile
> doesn't seem to be considered to be particularly important.

Was for me. I got one from work to test (at the time it was a prototype
not yet on general sale), and having a consumption figure on the wall
(whether precisely accurate or not) stopped my lodgers leaving all the
lights on all the time. Since I pay the bills (their rents are
all-inclusive) that's a win as far as I'm concerned :-)

Pete

Hugh Jampton wrote:
> On Thu, 13 Nov 2008 15:18:11 -0000, Paul wrote:
>
>> its not this one is it?
>> [..]

> That's the one !

Ah ha - that's the one I was testing :-)

Not sure to what extent they publicise the fact, but it has a serial
port on the bottom which lets you connect it to a computer for remote
monitoring, pedantic graphing, etc. One of our Master Inventors (
http://earth2tech.com/2008/04/30/the...ts-energy-use/
) was handing them out on the condition that we hooked them up to a
system at work that graphed everybody's power usage. Mine's no longer
connected; the number on the wall is enough for my needs.

And no, I didn't have every detail of my house hooked up to Twitter -
that's just Andy being Andy :-)

Pete

"Pete Verdon" <usenet> wrote in
message news:ecb4
> Hugh Jampton wrote:
>> Ah ha - that's the one I was testing :-)
>
> Not sure to what extent they publicise the fact, but it has a serial port
> on the bottom which lets you connect it to a computer for remote
> monitoring, pedantic graphing, etc. One of our Master Inventors (
> [..] )
> was handing them out on the condition that we hooked them up to a system
> at work that graphed everybody's power usage. Mine's no longer connected;
> the number on the wall is enough for my needs.
>
> And no, I didn't have every detail of my house hooked up to Twitter -
> that's just Andy being Andy :-)
>
> Pete
>

what software did you use to record the results?

On Fri, 14 Nov 2008 01:19:45 +0000, Pete Verdon wrote:

> Ah ha - that's the one I was testing :-)
>
> Not sure to what extent they publicise the fact, but it has a serial
> port on the bottom which lets you connect it to a computer for remote
> monitoring, pedantic graphing, etc. One of our Master Inventors (
> [..]
> ) was handing them out on the condition that we hooked them up to a
> system at work that graphed everybody's power usage. Mine's no longer
> connected; the number on the wall is enough for my needs.

Interesting :-)

I noticed the serial port but unfortunately I don't have a serial port on
my PC. Might play around with a serial to USB converter but the last time I
did that (weather thingy) it failed.

Ah well - another toy to play with :-)

In article <afa7t7011313$.eojqp7e6gcbu.dlg>, Hugh Jampton
<me> scribeth thus
>On Fri, 14 Nov 2008 01:19:45 +0000, Pete Verdon wrote:
>>Interesting :-)
>
>I noticed the serial port but unfortunately I don't have a serial port on
>my PC. Might play around with a serial to USB converter but the last time I
>did that (weather thingy) it failed.
>
>Ah well - another toy to play with :-)
#
There are PCI COM port boards such as these and they are around half that
price. We've got some to add in a few extra COM ports on a couple of remote
machines....



http://www.serial-cards.co.uk/produc...tegoryid=52637