# How long does it take for electricity to be considered OFF by general appliances?

I'm looking for an ATS (or DIY) to switch between my solar and grid power.

I've seen some automatic ATS like here

I've seen on youtube someone uses this model and his computer is switching between solar and grid without "power cut". According to the details of the product : "Transfer Time:≤10ms".

Transfer time is so low that the computer didn't see it as a power cut.

What are the factors that can influence this ? Is it related to the appliance ?

I was expecting the computer to turn off and turn on again. Do you know what is the maximum number of ms that will trigger a "power cut".

Will it be difficult to DIY ?

• it can actually be done so quickly there's no noticeable drop out whatsoever, if started just before a zero-crossing. Most common relays take longer, 20-40ms iirc. Commented Jul 30, 2019 at 21:38
• Most devices have components called "capacitors", which can store a small amount of electric charge. There is normally a bank of large capacitance at the power input to the device, and these capacitors help filter out noise (variations in the input voltage) and present a stable voltage to downstream electronics. How long that'll last once power is cut depends on the design of the device and how much power it is dissipating at the time power was lost. Commented Jul 30, 2019 at 21:58
• When designing a piece of test equipment years ago, we needed to ensure that data was properly written to an EEPROM if power was lost, so that the data was not lost. We figured we needed 10 ms to accomplish this. We measured how much power the equipment needed to operate, and ensured we had enough capacitance to get that last gasp task accomplished. The time we chose was to solve a design problem specific to this device. Commented Jul 30, 2019 at 22:00
• Capacitors cost money, and minimizing the components in a product is important to the bottom line. Commented Jul 30, 2019 at 22:00
• BTW, you can see this with something like a laptop power supply. There is usually an LED on the brick. If you unplug the brick from the wall without the laptop connected, that LED will remain lit for a long time. Plug it into the laptop and it'll probably go out very quickly. Here, the load at the time of power loss is being changed, and the LED is the "capacitors still have some power in them" indicator. Commented Jul 30, 2019 at 22:02