This post is part of a series as I try to get a handle on power usage and reduction of it…. if possible, in my home.
Over the past year I have been slowly adding power management hardware to many devices in my house, either via ZigBee power management plugs, inline ESP based devices or in the past few months a Wi-Fi connected clamp meter from Shelly.
The accuracy of these plug devices is oft disputed, and calibration is a must to get the most of these devices, ensuring they are accurate. I found on initial testing with the clamp meter by using a known load it was very accurate, so no additional calibration was required.
The simplest method of doing this I found was with a lamp with a defined wattage bulb. At the time I felt this was close enough, but I might revisit it in the future.
For the plug-in devices, they have been swapped, stopped and dropped so many times that they need recalibration but for the moment they give a good general indication of what the worst offenders are. At the moment the single biggest power user in my house is my network switch. To be fair it is powering several devices via PoE but it’s very old and by no means efficient.
I only really had three options of whole home power monitoring. A system like home assistant glow, where I used an optical sensor to record the pulses from the meter. An ESP32 with an OCR sensor to read the display on the meter or the clamp meter. The first two required battery based setups and despite the space in the cabinet I did not want the possible hassle of setting up inside it, aligning devices and also explaining to the provider, what the hell they were in the event of any queries arising. This meant that the clamp meter was the victor.
Installation in my house proved difficult as I could not get a clamp into the place it needed to be without first detaching the mains cable feed. This is not something I wanted to do as not only did it mean killing all the power in the house from the outdoor switch but also means stepping into an area that should only be left to the electricians.
The board is fairly full, so space was at a premium, but with a lot of persistence I managed to get the clap meter installed on the mains feed and the EM itself wired up on the other side of the board. Thankfully its very close to the Wi-Fi AP, as such a small device, behind a cover, behind another cover behind a metal door, had me sceptical that I would get it connected. Be sure your +/- for the clamp meter is the correct away around, otherwise it will report your power consumption as return to the grid as opposed to consumed.
Once installed, I used the Shelly App to setup the device but opted not to use the cloud function as it will be reporting directly to Home Assistant and one cloud connection is enough. The device itself supports storage of 365 days of info so even if Wi-Fi is offline I was assured it would have the information available when connection was restored.
Right away it showed the input Wattage and Voltage.
I opted to let it run for several days without any interference just to ensure it was collecting information reliably before integrating it into anything and to ensure there was no Wi-Fi dropouts that would have to be dealt with.
To add the device to home assistant, its as simple as adding the integration via Devices and Services.
Once discovered, the device will show up with the entities available for view. Unless you are using a static IP assigned from your router, it might be best to us the hostname of the shelly device.
You also get access to additional functions the are quite useful for not only updating and rebooting but also in relation to the switch function itself.
So now we get to the useful bit, the monitoring.
After leaving it for a few months I decided to compare with my electricity bill usage. My provider gives a bill every 2 months but at least its marked with the dates. I could compare this date period to the long-term statistics within home assistant.
As mentioned earlier, I don’t have a smart meter yet so this is as granular as I can get from a provider point of view. The euro rate per unit is available on their website and at the moment I am manually inputting it but need to set it up to be scraped to ensure its accurate.
I discovered that the values from my monitored dates are slightly different to that on the recorded units on the bill. I thought this was a case of the unit under reporting as I checked the units on the meter, and they are accurate to the that on the bill.
This was a simple case of knowing when the local meter reader was coming so once he left, I took a photo and compared it to my bill when it arrived. Bit of a long-winded process but I was unsure of any other way to ensure I could have an accurate measurement of their reading. Again, working from home during covid had its benefits. The sooner my smart meter is installed, the better.
Adding to the difficulty in verifying this information was that in February and March, the Shelly device lost contact with the AP and instead of having predictable values for each day, I got a bulk report on the 21st of Feb and the 2nd of March, as you can see below. Thankfully though, my previous billing period was November – December and they were just fine. Although a little bit frightening with the exaggerated power usage that comes with Christmas.
At the moment, these figures on their own only serve to backup that my bills are too high and if steps I am taking are having an immediate impact. Combining them with the plug and inline monitors gives a far better overview.
By subtracting these monitored devices, which include my network equipment, washer, dryer, fridge, dishwasher, consoles and similar from the total. I also play on adding a second clamp meter to monitor the lighting circuits. This should leave me with a minimal amount of unaccounted power usage in the house. I will update this series with how I managed the plugs and inline monitors which is fair more technical that this post.