PV generation and consumption monitoring help please!

Would really appreciate guidance from the community on the right hardware and how easy it is to use for a complete beginner with limited IT skills!

I am a domestic energy adviser looking primarily at the feasibility of battery storage in customers homes. I believe key is understanding house load, no point in recommending storage which is never fully charged. As part of may service I monitor house usage, initially for a month, and need equipment to do this.

Although there are a number of energy monitors, nearly all have CT clamps to monitor the PV and I do not want to open up generation meters or consumer units to get to the live.

Would the EmonPI work with the pulse meter and one CT clamp for consumption, for my purposes? Does this show the PV output on the webportal? Is this easy for a IT novice to set up?

Thanks for your help.


Quite a few people start here as complete beginners with limited IT skills. It’s a steep learning curve, but as long as you don’t assume that we know what’s in your brain, and tell us the full story, there are a lot of people here willing to help.

I’m sure you must know how energy meters work, but in case not, the LED (visible or I.R.) will only flash for power/energy flow in one direction. If you equip an emonPi with an optical pulse sensor, then you can use that to count pulses from one meter. Unfortunately, the microprocessor that we use cannot handle two pulse inputs, so you do need a current transformer (please, not a clamp, that’s something carpenters use) for any other circuit. As you’re in the UK, the meter tails are normally easily accessed so a split-core c.t. there will measure either nett grid power or (if you’re downstream of a Henley Block where the P.V infeed connects but upstream of the consumer unit) house consumption.
Once you have the numbers into emoncms (running on the emonPi, presumably), you can do what you like with the data. There’s a small limitation with pulses - you are of course limited to 1 pulse’s worth of granularity, so you’ve no idea what is happening between pulses.
You will need a twin mains socket reasonably close to the meters, as the emonPi needs both a 5 V d.c. supply to operate, and an a.c. adapter to monitor the voltage, unless you can forego some accuracy and a knowledge of the direction of power flow. Depending on where the P.V. infeed is and where you can put your c.t., it may be possible to operate without the a.c. adapter.

Finally, I can’t say how easy it is for an IT novice. We try to make it easy, and there’s always help here on this forum.

Hi Robert
I decided that I did feel brave and have purchased an EmonPi, however my first attempt at monitoring Solar generation and house consumption has not gone to plan!

Briefly the set up:

-CT1 on incoming live is pointing away from the grid
-CT2 on live PV is pointing towards the grid
-There are no power sockets anywhere near so I have used an extension lead to plug in the EmonPi, but I have not plugged in the a.c. adapter (does this need to be deleted from the list of feeds on site? will it work without it?)

I set up Emoncms (I have not set up remote access yet) in line with a “type 2” solar system as the PV is feeding directly into the consumer unit.

Current position:
-This morning was cloudy and the PV was generating around 500w.
-The washing machine was on (old hot water fed), the hoover briefly and a couple of fridges.

-CT1 was showing an output continually just lower than CT2 and that the house was importing all morning.
-CT2 was showing an output slightly higher than the figure shown on the front of the inverter.
-The Solar App was adding Power 1 to Power 2 for the consumption.

I tried to change the CT clamps in both directions and in different positions, but no change. I also checked what I had entered to power 1 and 2, but I couldnt see what I had done wrong.

I am sure it is a novice mistake, but I can not work out what I have set up wrong and I would really appreciate your help. I do have lots of pictures if that helps.

Kind regards


That is because you don’t have the a.c. adapter, so there is no reference to determine the direction of power flow. (Read about it in Learn.) Your problem is, although you can assume the direction of power flow in the PV connection, you cannot know the direction of power flow in the grid connection.

If you’re going to run without the a.c. adapter, you need to measure the current where you know - or can assume - the direction of power flow, and that is a “Type 1” installation. Although it’s not clear on the diagram, you can have the a.c. adapter for a “Type 1” set-up, you must have the a.c. adapter for a “Type 2”.

So it is possible to run the Pi without the a.c. input, but not with the way your PV is wired. You’d need it to feed into Henley blocks on the grid side of the C.U, so that you could have the “house” c.t. measuring house consumption.

I think those two have something in common :innocent: You need to get the a.c. adapter connected. And power up the Pi at the same time or after you’ve connected it, not before.

Thanks Robert, that is really helpful. Would you recommend installing a socket near the consumer unit. Other than plugging the AC measure into an extension lead,there are no sockets anywhere near.
Kind regards Anthony

That would be the most convenient (I presume), easiest and simplest place to add one.

Hi Robert
Just thought you would like to know that installing a double socket worked a treat and all up and monitoring. The instructions are very clear and was able to set up the basic Solar App on site and remotely.
Thanks for your help and patience!

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