Tapo P110 does NOT give you an accurate estimate of electricity usage

Andrea15

I thought this deserved its own thread.

I have been playing with the Tapo P110 to find out how to decrease me electricity usage by ascertaining how much my appliances cost to run.

Now I can tell you for a fact that my gadget does NOT tell the truth.

I have been running my washing machine on my usual cycle (30 °C, 2.5 hrs approx) and the Tapo says I have used up about 0.55kWh. However, looking at the meter I know that the usage is approx. 1 kWh (and yes, I have taken into account background usage, and yes I have repeated the experiment).
If I knew that the Tapo is always about 40% off then I suppose I could scale everything up, but who knows if that is the case.

Bottom line, the figures you get from the gadget may well be unreliable (and they most certainly are in my case). Maybe I have a duff unit... Is yours?

MattMattMattUK

I have eight of them and they all seem to be accurate, they are in line with what I would expect from the devices plugged in, stated ratings, against a watt meter on the PSU of my PC etc. You could compare it against a few things of known draw to see if aligns with what it should. 

0.55kWh would be entirely reasonable for a 30c cycle, so variations in background usage and/or rounding on the meter could potentially account for the difference.

Andrea15

Matt, my washing machine is elderly, but, that aside, either the tapo fibs it the meter does.
The dishwasher uses up an amount that is consistent with the label, so the meter looks right (being fitted, it is too much of a hassle to plug the tapo).
As I said, my unit could well be faulty, though. 

CSI_Yorkshire

I think it's unlikely that it's reading half of the actual consumption.  

If that was true, your old FF would have been using enough energy that you never needed heating.

Andrea15

Where else could the usage come from?
Measured it twice in different days.
A usage of 1kwh per wash, though high by today's standards, doesn't seem outrageous.

Eldi_Dos

@MattMattMattUK:
                Why would you want eight of these Tapo devices, most of us are trying to cut down on consumption.

CSI_Yorkshire

Eldi_Dos said:

@MattMattMattUK:
                Why would you want eight of these Tapo devices, most of us are trying to cut down on consumption.

To measure eight different things at the same time.

The power consumption of the device itself is effectively zero.

Eldi_Dos

CSI_Yorkshire said:

Eldi_Dos said:

@MattMattMattUK:
                Why would you want eight of these Tapo devices, most of us are trying to cut down on consumption.

To measure eight different things at the same time.

The power consumption of the device itself is effectively zero.

I was meaning consumption in the broader sense not just power consumption.

Andrea15

CSI_Yorkshire said:

I think it's unlikely that it's reading half of the actual consumption.  

If that was true, your old FF would have been using enough energy that you never needed heating.

Re FF, I was wondering about it myself.
I don't know how the tapo works. The distortion could be non linear.
Unlike the fridge, the washing machine registered a very large spike in voltage at the beginning of the cycle. Might that affect the reading?

CSI_Yorkshire

Eldi_Dos said:

CSI_Yorkshire said:

Eldi_Dos said:

@MattMattMattUK:
                Why would you want eight of these Tapo devices, most of us are trying to cut down on consumption.

To measure eight different things at the same time.

The power consumption of the device itself is effectively zero.

I was meaning consumption in the broader sense not just power consumption.

And if you want to measure 8 things at once, having 8 measurement devices is a requirement.  Failure to fulfil a requirement is not a good argument for reducing consumption.

Andrea15 said:

CSI_Yorkshire said:

I think it's unlikely that it's reading half of the actual consumption.  

If that was true, your old FF would have been using enough energy that you never needed heating.

Re FF, I was wondering about it myself.
I don't know how the tapo works. The distortion could be non linear.
Unlike the fridge, the washing machine registered a very large spike in voltage at the beginning of the cycle. Might that affect the reading?

It's possible.  How big a spike are you talking about?

Andrea15

CSI_Yorkshire said:

It's possible.  How big a spike are you talking about?

This spike. Same thing happened yesterday. 
(I had to reconfigure it because for some reason it couldn't be found. That meant moving the washing machine )