I’m planning the IoTaWatt installation for my house in the US, split phase. I have two 200A panels and solar feed into one of the panels. Since I’ll need six CTs/inputs just for those feeds, it only leaves me with eight remaining inputs. What would be the best configuration if I want to monitor 18 other inputs (in addition to the six feeds)?
You can consolidate circuits. Two (or more) circuits (on the same phase) can go through a ct to give a combined reading.
Alternatively get a second iotawatt and use influxdb to consolidate the data. Grafana to report it.
I would urge you to define your purpose for measurement. Is it to drive behaviour change? Spot ‘bad’ devices? just for interest? What is the data worth to you? The answer to those questions will dictate the approach you take.
The circuits you don’t measure can be calculated (in plus solar minus measured circuits = unmeasured circuits.)
Some circuits will be irrelevant to your core purpose - lighting?
If you are investigating a problem then don’t forget CTs can be moved between circuits - just update the setup to reflect the circuits being measured.
I ended up with two iotawatts because my boards were too far away from one another to use a single unit. I use influx/grafana to monitor but usually the iotawatt data itself to investigate if something seems off. I have many circuits that are unmonitored because the usage is low.
You do really need to define what you want to gain from the purchase. I have been monitoring energy usage for about 25 years. I remember the first time I got data back back from a project installation I was on. This was just whole house utilization, but it was almost 30 years ago and the data was realtime. There was no visualization, yet it was still magical.
But, that magic wears off pretty quickly for most people. If you are interested in reducing base load (what is always on) you don’t really need more than the mains, but it is a lot easier if you have more circuits monitored.
I currently have 2 Iotawatts, but will probably be getting a 3rd soon. I am not sure I need it, but it isn’t that expensive and it will be interesting to have more distinct data.
Thanks for the valuable insights. This got me thinking about making a list of the circuits I want to monitor and listing my reason for monitoring. Here’s what I came up with:
One of the things that got me interested in the whole effort was related to the solar panels we had installed in June. I’ve enjoyed the lack of an electric bill the past six months, but noticed that our energy usage went up considerably in Dec. I couldn’t figure out why because we were not running AC units and have gas heat. This got me thinking about the EVR (Energy Recovery Ventilator) and it’s preheating coil. It was cold in Dec, so I’m sure the electric preheating unit must have kicked in. (I’m trying to avoid using up all my credits from net-metering, so that we can continue with no electric bills!)
I figured since I was going through the effort to monitor the ERV, why not look at other things that I could either take action on, or that I was just curious about. I like the idea of getting inside the service panels once to add CTs, rather than moving them around to explore other curiosities.
Glad to know I can combine the data from two Iotawatts. I need to start researching influxdb and Grafana. I hope I can use these without monthly fees. Any tips on learning those, or advice on implementation?
Those do all look like they could be interesting. It depends on how much computer knowledge you have how hard it would be to learn and self-host InfluxDB and Grafana.
Many people run them on Raspberry Pi machines. I always thought they weren’t that great on price/performance and that was before the still present “supply chain difficulties”. I have always an old laptop, but recently switch to a mini PC. It is at least 10x powerful but only a few watts more.
When I first started I ran Windows on the laptop and left it running always. That generally worked but recent versions of Windows don’t really support that usage very well anymore (as they expect a human to be there).
I used Proxmox for a while and it is good, but it has a steep learning curve. I am in the process of redoing things and am now using Ubuntu with Docker and Portainer to run things (InfluxDB, Grafana, Node-RED) in containers. The goal is to make it easier to update them as they change. There is a bit of a learning curve.
There are lots of tutorials on the internet for just about any technology. There is a lot to learn, but you don’t have to learn it all to get started.
If you don’t have the technical skills, emoncms should be able to do aggregation of multiple inputs into a feed. I have not tried that directly. I liked emoncms a decade ago. I like the appearance/usability of Grafana a lot more, but still have some stuff in emoncms and buy credits regularly, because that is easier than doing the work to move stuff (and I still want the data).
I decided to skip the microwave and dishwasher, but just ordered what I needed for everything else.
I’ve done some tinkering with Raspberry Pi, Arduino, Python, etc. So I hope I can figure out what I need to put InfluxDB and Grafana to use. Need to find a little time to research. May eventually try to use the data with my home automation system and provide warnings for particular events such as “no refrigerator current for the past 4 hrs.”, “Radon pump not running”, or “EVR not running”, etc. This should be fun and a good learning opportunity.
These folks have provided good advice. I only have a couple of additional comments.
Radon fans operate 24/7 and there are no real variables. The head stays the same and the temperature of the air being extracted is constant. You can just measure what it uses once, or even just go by the nameplate rating for most installs.
Many solar inverters are connected two-wire (no neutral). If that’s the case, you will only need one CT to measure it.
Household dishwashers don’t t typically use a lot of electricity. Ours uses about 0.6 kWh per run. Maybe if you do a long cycle with “sani” heating you would use 1 kWh. I advise measuring things that you might want to change. What would you do as an alternative to using your dishwasher? Hand washing uses more hot water and doesn’t do as good a job.
Good point about the solar inverters not having a neutral. Oh well, I’ll have an extra 200A CT. 
Yes, I understand the radon fan runs all the time and not much interesting happening there. Except for the fact that I would like to know if it dies. I’m hoping to monitor it for that purpose so that I can receive a notification if it fails. I haven’t done the research yet, but I’m assuming that with the ability to pull the data real-time, I should be able to automate a process that would notify me if the unit dies.
I did take the dishwasher off my list of things to monitor.
Thanks for your input.