NOOB: monitoring solar generation AND home energy usage

Hi There,
Am trying to work out what I need to do the following
1 Get usage data on electricity user throughout the house
2 - get generation vs consumption data for slar pv panels

my question is do I need to 2 emonPis for this or is one sufficient as I cant tell from the docs

thanks in advance

sorry more information i should have added - i have an openHab setup running on a Pi which gives me heating data so want to add power usage to this. eg I will have a local collector running on my network so dont need emonCMS - not sure if I need emonPi for this or something more simple. any help greatly appreciated


the following is on the basis you have a standard domestic setup.

The EmonPi will give you this (or an EmonTX plus an EmonESP or direct serial connection to a Pi (or clone)).

You don’t need Emoncms. Others use InfluxDb and Grafana for their dashboards. You will need to consider how you access the data. However it is free and often the best point to start.

How granular? If your distribution board allows it you could add a CTs to a couple of circuits else look at the multitude of power sensing ‘smart plugs’ out there to give per device measurement.

Hi @borpin thanks for the swift reply…

Makes sense on both points - the only question i have before jumping in is can i monitor solar pv and energy usage with the same emonpi or do i need 2?

Thnaks again


An emonPi has two inputs to measure the current. Current transformers, each with approx 1 m of cable, plug in to those inputs. Provided that you can get at the (single, not 2-core or 3.core) cables within that distance of where you will have the emonPi, or you’re able to extend the cables (a bit of soldering is needed, because a pre-assembled “headphone extension” isn’t very good for this purpose) then one emonPi will measure both quantities.

Even if the distance is too great or the extension cable impractical, there are still cheaper ways than a second emonPi - e.g. the emonTx that Brian mentioned - to send the second lot of data to your emonPi by ISM band radio.

If you post a photo of where your incoming power / solar is, we can advise.

I bumped your trust level so you should be able to post photos.

attached - thanks again :slight_smile:

Would a somewhat wider shot be possible? I can’t see where the PV infeed is. There are two (16 mm² ?) cables going to the left out of the Henley blocks and up the left-hand side of the consumer unit, and I can’t see where the cables come out of the PV isolator. Are they in fact those, and they’re routed in the trunking and come out out-of-shot somewhere above the consumer unit, only to come down again to the Henley blocks?

hi guys,
sorry for the delay - anyway have tried to get a better shot…
is this ok to advise? there are no cables going into or coming our of the top of the consumer unit, seperate breaker for the solar pv is in the large white box and the solarpv meter is to the right of the white box


I’m afraid that doesn’t help. The real question is, where are those cables I referred to earlier going - the two cables (they look like 16 mm², slightly thinner than the ones going into the bottom of the consumer unit) that come out of the Henley blocks and up the left-hand side of the consumer unit.

I hope those are from the PV, but it’s by no means clear. If they are not, do you have any idea where they are going? Is there another consumer unit, or something like that, anywhere?

If we cannot identify the PV feed, the alternative is to measure the house consumption and the grid power, then the PV contribution must be the difference between the two. That makes the installation neither a “Type 1” nor a “Type 2” installation (Solar PV - Guide | OpenEnergyMonitor), which means the software may need a small adjustment.

So to the original question:

If you go down the emonCMS/emonPi route, I think you need only one emonPi, two c.t’s, an a.c. adapter and of course a 5 V d.c. power supply. You’ll need a double 13 A socket fitted close by.
Alternatively, if you want to avoid emonCMS and use another dashboard/database, then you want an emonTx with the ESP8266 WiFi module. You’ll still need the c.t’s, a.c. adapter and d.c power supply. The emonTx gives you the opportunity to monitor two more circuits (or groups of circuits) - provided of course there’s room inside the consumer unit for the c.t’s, and that could be a problem.

thanks for all the help guys - i went ahead and bought an emonPi - delivered today…

hoping to be promoted from NOOB soon :slight_smile:

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sorry having poked about it i think the answer is yes to this question

I think in that case you’ve got a free choice of what you monitor, so it should make it easy for you - you can set up as a standard “Type 1” or “Type 2” installation, whichever is the easier.

This is what I have to monitor my solar and power consumption of many circuits using a raspberry pi with Emoncms all with battery backup.


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Nice, clean installation, Alex! thumbsup

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