Hardware selection advice

Hi Everyone,

I’m looking for some advice on the best way to go with options for the various hardware choices. Hoping for some help here before loosing my marbles trying to understand the options.

What I’m looking for is something to monitor:

  1. Main power usage in the house
  2. Power usage to the garage
  3. PV generation
  4. Output from a (yet to be built) power wall.

Points 1-3 can all be measured from the one location whereas the power wall will be located c15 meters from the house.

I don’t need temperature or led monitoring. I also don’t need an enclosure or LCD screen, as the monitoring points are all relatively hidden away so all monitoring will be via the web, desktop PC or apps.

So I’m stuck on a few points…
Am I better with the emonPI + emonTX or emonTX + emonBase.

If I go with the emonPI, does this use the Pi V4 or an older version? Should I just get the shield and buy my own Pi plus sensors (works out cheaper) or is there benefit to getting the emonPI solar bundle?

I need 1-3 covered from the start with 4 being c6 months later so the emonPI solar looks a good option just don’t like paying for what I don’t need (ie lcd and enclosure).

Any help you could give would be really appreciated.

Welcome, Chris, to the OEM forum.

How will your power wall connect into everywhere else? Does it have to be monitored where it is, or can you measure the power flow where it connects (i.e. does/will it have a dedicated connection that you can access?

OK, that means that you don’t need an emonPi.
The quick and over-simplified description of what’s available is, the RPi Shield is the energy monitor part of the emonPi, and in turn it’s a 2-channel cut down version of a 4-channel emonTx. Normally, the emonTx sends by radio to an emonPi or emonBase, the Base being a RPi with a radio receiver but nothing else.

If you can measure all four cables - your main incomer/house supply, the garage supply, the PV infeed and the powerwall supply/infeed - at the same place (or within a few metres of the same place in the same area) then I think an emonTx with a wired serial connection to a Raspberry Pi (not even an emonBase) is your answer. Any Raspberry Pi will function - I have (or had while testing something else) a Pi 2B working as an emonBase, but it’s slow.

If it looks as if you won’t be able to measure the powerwall ‘at source’ along with all the rest, then it gets tricky. You will have to add an emonTx at the powerwall (just for one channel), then we need to figure out how the get the data to the RPi. The best hope is it’s within Wi-Fi range of your router, so we can add a Pi Zero W or an ESP8266 to it and get the data by Wi-Fi.

The Pi Shield won’t be very much use to you, because it has only two energy monitoring channels.

Interesting (to me at least!) that you make that observation. My emonBase runs on a Pi 2B (rev 1.1 with the 900MHz 32bit quad core CPU) from an SD card and has about 3.5 years worth of 3-phase consumption data and about 6 months worth of 3-phase solar data (total of about 46 feeds).
I’ve never noticed it to be particularly slow and I usually check my dashboards multiple times daily.

I imagine that any of the single core Pi’s would struggle though, top shows my long term average load to be 0.25 suggesting it consumes roughly a full core’s worth of CPU doing its normal thing without me loading up graphs etc.

It’s slow generating a busy graph that covers a long period of time - meaning months (the graph, not generating it :open_mouth: ). Anything else and, as you say, it’s fine.

Thanks Robert, really appreciate the info. I suppose I’m leaning to the Emonsheild and my own Pi so I can build as I go. The power wall is being build outside the house, don’t like the idea of all those batteries indoors. They may be fine at day 1 but what about at 5+ years.

So emonPI (via shield approach) for the first 3 channels and then the emonTX when the power wall is built.

Does anyone know the range of the TX or is that hidden in another post.


No - you can’t do that. The emomPi Shield has only 2 channels.

That depends very much on what it’s got to get through. A dry single brick wall or two is not much of a problem, soaked with rain and it’s heading towards questionable. 3 feet of stone infilled with rubble is a problem, as is foil-backed insulation. Given a clear line of sight, I can vouch for 30 m, 100 m is claimed, and more if you turn the power up (by default, we set the power below the maximum, because without an antenna, the radio can destroy itself transmitting at maximum power).

Thanks again Robert. I did miss the first obvious point on the 2 channels!