By design, the smart-meter is limited in how much data it can send back. You can choose to have readings sent monthly, weekly, daily, or half-hourly. There's no option for minute-by-minute precision. That's useful from a privacy perspective - and no doubt makes the network engineering simpler - but slightly annoying from a home-monitoring perspective.

The smart-meter has the ability to send real-time information to a local device using the ZigBee network. If you have an in-home display (IHD) then you'll have seen just how accurate it is.

As I've discovered, you can't just pair any-old ZigBee device to your meter. Luckily, Octopus have sent me the "Mini". A little device which connects to the smart-meter and your home WiFi, then reports usage every 10 seconds. Let's put it through its paces.

Size

Mini by name, mini by nature!

It's rare to find a device smaller than its plug. I half-wonder if they could have integrated it and just made it into a smartplug.

Annoyingly, it is micro USB. I am a USB-C maximalist. There's no reason this device shouldn't use the same cable as everything else I own.

Installation

Plug the Mini in - ideally within 5m of your smartmeter - and wait for the blinkenlight. Follow the in-app instructions. Because, like every modern device, it needs an app. You need to install the standard Octopus Android app, and can then add the Mini to your account and to your WiFi.

Like all cheap IoT devices, it will only work on 2.4㎓, so you may need to adjust which network your phone is on.

And then…

That's it. Every 10 seconds it sends an update to Octopus. You can use the app or the website to view your current consumption or to see your last 5 minutes or last 30 minutes usage.

If you're a dab-hand with the API, you can poll that. Or you can connect it to HomeAssistant.

Downside

In theory this is nifty, but there are a few things I'm not keen on.

• Export readings simply don't work for some brands of smart meter. That's an annoyance - my meter can send half-hourly readings for export, but the Mini just shows that I'm using zero Watts.
• No local connection. It sends the data to Octopus, so I have to use their API to get the data. I'd like the ability to stream it directly from the Mini.
• USB-micro. We live in the future. USB-C or GTFO!

Honestly, a bit disappointing. If you don't have solar panels - or your meter works correctly - this could be very useful. Even so, the lack of an local API is a bit of a buzzkill. Sadly, for my purposes, it isn't very useful.

The only problem is - I don't know how long the rice will take to cook. It uses "Fuzzy Logic" to work out exactly how much heat and time is needed for perfect fluffy rice. This is inconvenient. I cannot always hear the beep the machine makes when it completes its culinary wizardry.

So let's hook it up to the Internet of Things!!!

Step 1 - Get an Energy Monitoring Smart Plug. These are now relatively cheap and reliable. As the cooker is cooking, it reports back its energy use. But where does it report to? You can use the associated app, but that doesn't have an alert to say when something has stopped drawing power.

Step 2 - Install Home Assistant on a Raspberry Pi. HA is a nifty bit of software which gives you complete control of your SmartHome. It integrates with all the various makes and models of devices you have controlling your lights, TV, plugs, smoke alarms, and other gadgets. It comes with a companion app which runs on your phone.

Step 3 - After spending a few weeks configuring everything, getting frustrated, wiping everything, starting again, and then getting it right this time - you're ready to add some automation! I used Leo Fabri's Appliance Status Monitor. You tell it which plug you want to monitor, what power level to detect as "on", what power level to detect as "off", and how long it should be off before sending you an alert.

The user interface is... intimidating.

It is necessarily complex. But this definitely isn't for the casual user!

Step 4 - Test with users. My rice cooker dips in power a few times through its cooking cycle - which sent my wife scurrying to the kitchen expecting to be fed. After which, I eventually worked out that I needed to tell the monitor to wait for the power to have dropped for at least 60 seconds before sending an alert.

Step 5 - It works!

One minute after the end of the cooking cycle, I receive an alert on my phone. I can now go and eat. Lovely!

Is this worth it?

I like playing with gadgets - so yes.

I also don't want to eat over-cooked curry, or under-done rice - so also yes.

I am lazy and don't want to get off my arse every five minutes to check the cooker - so again yes.

I don't want my rice-cooker sending all my rice-cooking habits back to the manufacturer - so even more yes.

This is a fun project for adding a minimal amount of smart-alerting to your existing appliances.

And… it works!

Mostly

These are the Meross 315 Smart Plugs. They are small(ish), cheap(ish), and easy(ish) to use.

As soon as I plugged them in, before even configuring them, my home went crazy. I got a pop-up on my phone asking if I wanted to control them with Google Home.

Nope!

I then immediately got an email from Amazon saying our Echo had detected the device and perhaps I wanted to use that to control the plugs?

Also nope!

I wanted to add the plugs using the Meross app. Not because it is particularly good (it's basically fine) - but because of a couple of limitations in Matter. Here's a page from the plugs' manual.

At the moment, Matter doesn't support firmware updates. That's probably fair. You don't want some random app bricking your device - so it is restricted to the manufacturer's app.

But Matter also doesn't support energy monitoring. I understand it's early days for the protocol, but that's a bit annoying.

Luckily, HomeAssistant came to the rescue! Because the Meross API is well documented, my local SmartHome Pi was able to get a realtime view of how much power was flowing through the plug.

Minor irritations

The power toggle - and activity LED - is on the left side of the plug. That makes it a little awkward to press and obscures the view of the LED. I guess putting it on top would make it too easy to accidentally activate?

The energy monitoring doesn't seem to update in realtime in the app.

I renamed the plug in the Android app, but that name doesn't seem to be exposed in Matter. Nor was it picked up by HomeAssistant.

In order to connect the device to WiFi, your phone needs to be on that specific WiFi network. Because the devices only support 2.4GHz, I needed to swap SSIDs on my phone. But, on the plus side, I didn't have to manually enter any passwords.

But these are all fairly minor complaints.

Verdict

For about £32 for a two-pack (depending on whether the algorithm favours you) these are pretty good value for money. They were easy to set up, quick to get working in other apps, and had a firmware update waiting for me.

I got some Meross plugs about 6 years ago and they've kept trucking all that time - so I'm pretty confident these will last. And, even if Meross disappears, Matter means that another app can easily control them.

Next Steps

Here's the plan. I'm going to plug this into my Tumble Dryer and tell HomeAssistant to monitor its energy usage and send me a message when the drying is done.