Wesley's Tool-Box

Lots of companies are hopping on the wave of Internet of Things (IoT) these days, each trying to build an ecosystem of their own. Major Korean mobile carriers (SK Telecom(SKT), KT, and LGU+) are no different, each setting up proprietary efforts. I used to largely ignore them because they required monthly fee, ranging from a few dollars per device to tens of dollars for "unlimited" (discounted with multi-year contract). With many non-carrier solutions usable without fees, I felt this to be undesirable.

However, SKT must have felt that this arrangement was hurting their chances for wide acceptance, because it began offering some of their affiliated products free of monthly fees, charging only a nominal (KRW 5,500, US$4.80) one-time fee included in the sales price since last October. I decided to take the bait and started integrating their home IoT products, sold under the "SKT Smart Home" brand, into my house. The very first one was a smart plug. The one you see here is the one made by Witty.


Over time, I installed several of these plugs around the house and some of them came from another company, Dawon DNS. Because SKT was selling them, lots of things were made to be nearly identical, namely the packaging and the functionality. The frugal-looking brown paper boxes contain the plug and the instruction manuals, all of which look almost exactly the same except for the diagram of the plug. Both companies' plugs are controlled by the one and the same official app, and works largely like as if they are the same product.

Even the price is similar, at around $22.50 to $26, which makes them one of the most inexpensive options. This includes the aforementioned fee, so the pricing is rather aggressive. The deal is made even sweeter by the fact that the plugs do not need any gateways or hubs to operate as some other solutions do (namely that of other carriers'). It will interface directly via Wi-Fi, so if you already have a wireless router at home there's no additional cost involved.

It's been about five months since I installed Seojun Smart Meter at home and took various measures to cut down unnecessary electricity use. Now was a good time to see if the smart meter was recording monthly data accurately, and whether my efforts panned out well. This graph sums up everything that needs to be said.

In terms of accuracy, the smart meter consistently reported slightly lower than the default meter installed in the premise. However, it is more less in line with the advertised margin of error (1%) after the initial month and thus I think it's reliable. This is important because the companion app effectively shows last month's finalized data a full month before it shows up in the bill, and the app also shows the forecast for this month. Now I know that these values can be trusted and I can prepare two months ahead.

Moving onto the consumption trends, my home generally spent around 190 to 200kWh in winter, then fell down to the 170kWh range in spring if the family didn't go out on a vacation. This is already somewhat below average for a 4-person family, but I started making the house even less wasteful starting in February this year by making more efficient use of the appliances and changing the lightings and bulbs to LED. Eventually, it has settled to somewhere between 140 to 150kWh per month now. This is a saving of roughly 30kWh, or more than 15%.

Thanks to this and being much more aware of the consumption in real time, I'm expecting about 30% savings in electricity costs in the summer when the air conditioning is in full operation. Home electricity rates in Korea is pseudo-exponential, so you pay a lot less for seasonal increase if you start out from a lower baseline. Recently, I helped my dad cut down power use at his house by lowering the baseline by roughly 200kWh and I think it'll save him at least US$300 per month during summer. I'm expecting that the money that went into the streamlining will pay for itself in 3 years. Overall, I'm satisfied with the results of the efforts I put in.

As the hunt for even more potential waste of power continued, I brought in the help of thermal imaging technology. By scanning each place with a thermographic camera attached to an iPhone (FLIR One; I'll write about this later) I can find any hot or cold spots that seem to be out of place.

One of such "hot" spots I found was on the side of an air conditioning unit. It wasn't being used, but standby power drawn from the wall outlet was slightly heating up the control circuit and was readily visible via thermal images. I could just pull the plug until summer, but I decided to take a step further.


I replaced the default wall outlet with the one that had an integrated switch. This way, I could cut the power from the outlet with a switch when the air conditioner isn't in use, instead of having to pull the plug. Not only would this be simple to operate, it would avoid the mechanical wear. I should have done this ages ago.

As part of my ongoing data collection, I then tried to measure how much power the air conditioners in the house would consume while trying to cool the house. Sadly, the rooms were not hot enough for them to start cooling the air. I'll have to check them out again when summer comes.