How relevant is the energy consumption of IoT and RF home devices?

Question

I am designing and building my own house. I am very interested in automatizing several devices as blinders and lights.

In general, I am thinking in using Zigbee (Xiaomi and Aqara), RF and IR devices. The latter two will be controlled by a RF + IR controller.

Each device itself won't probably consume too much. However, imagine all my switches are connected and my blinders are always waiting for an RF signal to activate them. All those devices needs then to work with DC, which makes them, at least, need the use of an AC/DC converter.

How much could this devices consume? Is it relevant? Should I worry about it and try to reduce or optimize the number of connected devices?

Answer 1

Summary: Inevitably the additional smart switches will use some power, but it's probably going to be negligible compared to the other consumers in your home. I certainly can't imagine it being more than $50/year in electricity even if you run dozens of smart devices.

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As stated in How much power do smart sockets consume themselves? you can probably expect a smart socket (or similar device) to consume around 1–2 W. Wi-Fi devices will be on the upper end, ZigBee on the lower end (perhaps even 0.5 W). That figure of course includes all of the losses inherent in the electronics, but Bence Kaulics' answer there goes into more detail if you want to work through the calculations yourself.

For comparison, incandescent light bulbs easily use 100 W while running (so over 50 times the consumption of a smart socket). A newer LED bulb will still use about 10 W while running, so several times your smart switch's usage.

Say you installed 20 smart devices each consuming 2 W of power—that's 40 W. Generally electricity is billed per kWh (a ballpark figure is $0.12/kWh in the US—and about £0.12 in the UK, too). You'd use up 1 kWh every 25 hours, so you'd be looking at about $0.11 per day due to your smart devices, which is $40/year. That is of course some money, but if you used fewer or more efficient devices, that could be much less. 10 devices at 0.5 W, for example, cuts that cost by a factor of 8—just $5/year.

I would only worry about the power consumption of smart devices if you also care about how much your other electronics use, e.g. set top boxes, routers and so forth. Most smart devices use less than those and are designed more with power consumption in mind. If you're worried, consider checking the power usage of the devices you want to buy and add it up yourself. Likely you'll find the idle consumption of these devices to be quite low, fortunately.

Answer 2

Yes, it is perfectly possible that a domestic 'smart' installation will struggle to break even in term of saved energy - even though that isn't quite the question you asked.

The RF side is fairly efficient, depending on the protocol. A receiver can be fairly low power (finger in the air of sub 1 Watt), and even if the transmit side is 5 watts, the duty cycle is very low. The trick is that maybe you end up adding these to every bulb (which was 3-5 W initially), so your lighting has become ~20% less efficient. Actually, it's far worse because the lighting would only be on for a few hours, but the overhead is on 24/7. So you've potentially halved your efficiency.

Taking a step back, the resting load of your house is probably in the order of 100-200 W (assuming you're not wasteful, and not an agressive optimiser). In that context, adding a handful of extra devices won't burn a lot of power (compared to taking a shower or an extra round of hot drinks each day).

Where you can save is if you can make use of the smarts to improve your space heating or water heating (maybe also with follow-me lighting if you're otherwise missing this). Your big loads only need a small optimisation to gain back a worthwhile amount of energy - it takes some effort to determine that the house is empty and doesn't need heating, but you'll easily justify leaving the router on 24/7 to achieve this.