Home Energy Meter 29 January at 9:23PM in Green & ethical MoneySaving 4 replies 239 views

propnut

My smart meter IHD has been giving trouble for sometime now and although I have reported it numerous times to my energy provider they clearly have zero interest in replacing it.

As such I bought this from Aliexpress. 

https://a.aliexpress.com/_EzwkEQd

Now uptill now I had assumed that my IHD was giving a true reading and that my Myenergi EDDI was over reading however I noticed that this device was in lockstep with the EDDI. As such I used a clamp meter to measure the current  on my incoming line multiplied this by the actual house voltage =243v and hey presto it tuns out that it is actually the IHD that is under reading??

The above device is not the prettiest but it is very functional, provides current and historical data for hour, day, week etc and you can input your tariff to get a running view of costs. Which by the way have tallied with my actual costs on my providers page.

Petriix

IHDs often show incorrect information on cost because suppliers don't always set the tariff data correctly in the meter itself, relying instead on their own billing software. However the IHD usage data will mirror the metered usage exactly while anything using a CT clamp will be out by up to 10%. I pull API data from both Myenergi and Octopus and the Myenergi data is always a little bit out, especially at low usage levels.

zeupater

Hi

Is this a power factor issue? ....

Would an IHD connected to a smart meter be required by law to measure & display energy based on real power in order correctly bill for usage?

Would a device such as the one referenced have the capability of measuring actual voltage and both real & apparent power and therefore be able to perform the same functionality as the IHD ... or is it supposed to (and only able to!) just provide guidance?

Does the EDDI have the need to, the ability to, and moreover actually, take whole house voltage & load or even controlled switched load power factors into account, or is this superfluous to what is needed to do it's primary function, ie control supply voltage for proportional power diversion to a simple resistive load within the confines for simply not importing grid power ?

Could it therefore be the case that both the EDDI & energy monitor are the ones overreading energy usage based on power factor related inaccuracy and it's the smartmeter which is, by law, required to have a degree of accuracy that the other units aren't ?   

Just food for thought based on logical observations ....

Z

matelodave

As far as I can see both the EDDI and AliExpress devices use current sensors to detect the magnetic field around the cable to measure the current flowing through the mains input to derive their info.. The EDDI has the advantage of also being able to measure the voltage however I dont know if it does.

That is not the way an electricty meter usually does it. A leccy meter will normally have a shunt in series with the mains supply which measures the actual current rather than the estimated current from the magnetic field and so can measure the current to a much better accuracy than a clamp and take into account the instantaneous variation in voltage - my voltage varies between around 245 to 253 and so will be more accurate than a clamp.

As @zeupater points out the load on the mains is also subject to the vagaries of power factor, stuff with motors like washing machines, dryers, fridges, freezers etc have poor power factor as do LED bulbs (especially cheap ones).

AFAIK domestic meters dont take power factor info consideration(although industrial meters do). However as the waveform gets highly distorted when some of these load are on, then it will affect the accuracy of a current clamp more than it will a shunt.

Although you may be able to compare all the meters, there will be a difference between clamps and shunts which will manifest itself over time and will depend on what stuff is turned on and for how long. I'm also guessing that most of these clamp devices use the same Chinese chips and wont go through the sort of quality checking and testing that leccy meters have to endure.

They may be near enough for what they are intended but not accurate enough for billing purposes.

1961Nick

I have both Myenergi (CT) & Geo (LED pulse) monitoring & both are remarkably accurate.


January figures for import...

Meter: 652kWh
GEO: 649kWh
Myenergi: 648kWh


Jan figures for generation...

Meter: 162kWh
GEO: 161kWh
Myenergi: 160kWh