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
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.
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).
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.
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
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!
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.
its not this one is it?
Interesting site - thanks.
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
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 (
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?
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....
Apparently CurrentCost are now selling the cables from a "shop" on eBay, and have a USB version.
Pete
The feed out of the meter is XML in plain ASCII at 9600 baud. When I was still providing data to the system at work, I had a small low-power Linux system plugged into it. A Perl script there read from the serial port, extracted the power value (the XML also contains temperature and various historical values which I wasn't interested in), and used an MQ Telemetry Transport library to publish a new value to the central broker every time it changed by more than 100 watts. My colleagues have reinvented the wheel many times over with graphing and notification gizmos subscribed to these power feeds.
I've been meaning to write my own script to put values into a database and do various reporting on them (predicted bills and so on) but it's fairly low down on quite a long list :-)
In summary, I'm not aware of any generally available software, but if you have the skills it's very easy to hook things up to it.
Pete
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