Thinking About Smart Home Power Usage • Hacker News Board

Re: Thinking About Smart Home Power Usage

#11

Post by bcrosby95 » Thu, Feb 13, 2020, 9:30 PM UTC

Someone wrote: post #3

I never understood the claim that smart switches on LED lightbulbs will conserve energy. The duty cycle of the average light bulb is fairly low; I would guess they are switched on for If so, adding a ‘smart switch’ that uses 0.5W to a lighting fixture that has a 10W LED light bulb increases its average power usage by about 50%. You must be fairly sloppy to make that a gain, compared to a manually operated switch.

Lots of people have gotten lazy about turning off lights since LED is so cheap. E.g. I think our kitchen light is on around 12 hours per day because the switch isn't very convenient. Or the garage light - if it's left on during the day, it probably won't be noticed until morning.

Also kids tend not to turn lights off.

But yeah, even if you are saving money, smart switches are pretty expensive. It will take a while to recuperate the extra $ and time invested.

I would focus on switches that control several lights at once. E.g. our garage lights use 100 watts in all. Kitchen uses 65. Hallway 50.

Re: Thinking About Smart Home Power Usage

#12

Post by Bedon292 » Thu, Feb 13, 2020, 9:36 PM UTC

cushychicken wrote: post #6

We used to use those Kill-a-Watt probes at work to classify smart home device power draw. Emphasis on "used to". They are not very accurate at all, and the sampling interval over which they take data on wall power draw is slow enough that you will miss important changes in current draw on your DUT. We have since switched over to expensive, calibrated Agilent power analyzers with better time resolution. The post is we…

Do you have some of that data available? I think his data does seem off, but all these always on devices have to be costing something right? Curious what that cost actually is.

Re: Thinking About Smart Home Power Usage

#13

Post by floatingatoll » Thu, Feb 13, 2020, 9:36 PM UTC

function_seven wrote: post #2

> The real shocker was when I decided to measure only the Wemo mini smart plug with nothing connected was costing me $0.31/day. I can't buy this. That's 3,100 Wh each day, or roughly 130W constant usage. That much energy being dissipated in the plastic housing would be burning hot to the touch, or melt it. I'd wager he's off by a couple orders of magnitude. 1.3W is much more likely for a smart plug to draw. The 55W h…

To calculate the math more correctly, a 1W smart plug is contributing $0.09/month to the $400 electrical bill quoted. This is a stellar example of a micro-optimization, in programming terms.

Focusing on big spenders like "anything with a pump" and "anything that generates heat" would contribute significantly to reductions.

I once upgraded video cards, reducing my computer's power draw by 180W and lowering my electric bill accordingly. This was back in the early days of CFLs (they were terrible) so it may not seem like much, but it was on 24/7 and that was the power at idle. I think it worked out to something like $10/month of savings, which was quite noticeable for my total bill of $50 or so.

Re: Thinking About Smart Home Power Usage

#14

Post by [deleted] » Thu, Feb 13, 2020, 9:37 PM UTC

barbegal wrote: post #4

The problem of saving power with small household devices is similar to the problem with micro-transactions. The overhead of connecting devices into a smart system is far greater than the recovered cost in terms of both money and energy. A smart switch can easily run to $100 to purchase and install and $10 a year to run. So it needs to save you ~$20 a year to be worthwhile. For large appliances that are regularly used…

[deleted]

Re: Thinking About Smart Home Power Usage

#15

Post by Bedon292 » Thu, Feb 13, 2020, 9:41 PM UTC

barbegal wrote: post #4

The problem of saving power with small household devices is similar to the problem with micro-transactions. The overhead of connecting devices into a smart system is far greater than the recovered cost in terms of both money and energy. A smart switch can easily run to $100 to purchase and install and $10 a year to run. So it needs to save you ~$20 a year to be worthwhile. For large appliances that are regularly used…

While they may not actually save money over lifetime, its possible they do reduce your carbon footprint over their lifetime. I am actually curious about that side of things. The devices obviously cost some amount of resources and money, does their electricity savings every offset their initial creation.

Re: Thinking About Smart Home Power Usage

#16

Post by hotswapster » Thu, Feb 13, 2020, 9:43 PM UTC

I had this scenario too. I purchased PowerTag by a Schneider Electric and then tied this into Home Assistant via Node-red. This gave me usage on individual circuits and automation resulted in a 40% reduction in energy usage.

For curiosity I wired in an SDM eBay brand meter and it was within 1% of the Industrial grade PowerTag.

Another option is emonpi and it’s easier to install than both of the above.

Happy metering! (Oh and you’re lucky, Power in Australia is $0.28/kWh

Re: Thinking About Smart Home Power Usage

#17

Post by kcmastrpc » Thu, Feb 13, 2020, 9:44 PM UTC

How do you turn off smart bulbs which require power to retain connectivity settings/configuration?

Re: Thinking About Smart Home Power Usage

#18

Post by aequitas » Thu, Feb 13, 2020, 9:46 PM UTC

In the Netherlands when smart meters where introduced one of the requirements was that the meters should have a port with a defined standard (DSMR[0]) which could be used by the house occupant to read metrics for themselved. The standard is pretty well setup with newer versions giving per second power/gas usage readings in human parsable ascii over rs232 on an rj11 connector.

[0] https://www.netbeheernederland.nl/_upload/Files/Slimme_meter...

Re: Thinking About Smart Home Power Usage

#19

Post by cushychicken » Thu, Feb 13, 2020, 9:51 PM UTC

Bedon292 wrote: post #12

cushychicken wrote: post #6

We used to use those Kill-a-Watt probes at work to classify smart home device power draw. Emphasis on "used to". They are not very accurate at all, and the sampling interval over which they take data on wall power draw is slow enough that you will miss important changes in current draw on your DUT. We have since switched over to expensive, calibrated Agilent power analyzers with better time resolution. The post is we…

Do you have some of that data available? I think his data does seem off, but all these always on devices have to be costing something right? Curious what that cost actually is.

I don't - it was collected for work, and I'm not allowed to share it.

Re: Thinking About Smart Home Power Usage

#20

Post by mikequinlan » Thu, Feb 13, 2020, 9:57 PM UTC

kcmastrpc wrote: post #17

How do you turn off smart bulbs which require power to retain connectivity settings/configuration?

My Hue smart bulbs retain connectivity and configuration settings when powered off (via the light switch). If they didn't it would be awful -- you would have to reconnect and reconfigure every bulb in the house after each power outage. I assume the data is stored in some kind of flash memory.