Project Start with Black Friday Deal
On Black Friday, I ordered 4 Tapo P115 for less than 40€ and started diving into the following rabbit hole that I will describe here. The main reason why this setup works is due to the power measurement capabilities of modern smart plugs.
Hardware Needed
- 3x Smart Plugs with power measurement
- 1x Motion sensor
- 1x Wi-Fi Router
Initial Situation
I have one workroom with 2 desks and a lot of devices that draw power in standby mode. The combined consumption is about 16W during standby. About 2/3 of the time, all devices are in standby mode, costing me over 20€ per year with current German energy prices.
Solution
All devices with standby usage are connected via a single power strip. So, why not place a smart plug before the power strip and switch it off if the power draw is at the standby level of 16W or lower? This worked, but every time it powered on again, the trip switch activated. I am not 100% sure why, but if I switched on some devices one after another, this could be prevented.
The final solution was to use 3 power strips, each controlled by a smart plug:
- Plug 1: Switches off the main power strip that contains the other 2 power strips and central components like a network switch.
- Plug 2: Contains all devices for Desk 1.
- Plug 3: Contains all devices for Desk 2.
This setup at least prevented the trip switch from activating.
Automation
Shut Off
The first step is to determine under which conditions to power off the strips. The triggers I used are the power consumption of the plugs for each desk and the main strip. If the standby consumption is present for at least 3 minutes, the strip is switched off. Before switching off the main strip, I have to ensure that the other two strips are off, to avoid them turning off as soon as they get power again (Tapo plugs do not have an option to restore power; my ThirdReality e2 plugs do, which is far better).
Side Quest
If I forget to power off my devices, a push message on my phone warns me in the evening, as soon as I plug it into the charger, to check the workroom.
Power On
I am using an IKEA Vallhorn motion detector to monitor the entrance of the workroom. As soon as someone enters, the main switch is triggered, and the automation checks who is at home using the Fritzbox (router) integration and the presence of each person’s smartphone in the home network. Based on these checks, the desks are powered on with the corresponding smart plugs or remain offline. If a person is in the home network but is not using the desk, it will power off again after 3 minutes. If this person enters the room, the check runs again and powers on the second desk.
Economics
- 3x plugs + IKEA Vallhorn: about 40€
- Working hours: I should not count them here.
- According to my calculation, it will save me 20€ per year.
- This calculation includes the self-consumption of the plugs: 0.6W in the off position and 1W in the on position. It might look better on your side as my problem was the trip switch.
Problems
- After some reading, I came across inrush current as a potential cause for the trip switch problems. Not sure if this is correct, but it sounds plausible.
- Check the maximum allowed current for each plug and power strip to ensure your devices do not exceed these values.
- Wi-Fi plugs are a bad idea: Zigbee is much easier.
- Some devices need a constant power supply, such as printers and the IKEA Megadesk.
Zigbee Advantages
- No online connection needed
- No app required for pairing
- No cloud required
- Faster connection to the Zigbee network upon powering on
Ideas / Projects
I also applied a similar automation to my Hi-Fi setup. It’s not much power in standby mode, but the time factor is crucial: it only runs for a maximum of 2 hours a day, leaving 22 hours per day in standby mode.