“Give the increasing power of the raspberry pi's you need an increasingly powerful power supply. An old phone charger use to be fine on older pi models but it's better now to have a few more amps to spare for reliable performance. It's also good to know it's from a reliable source if it's going to be left on 24/7”
“I tried a lot of normal phone chargers. Even up to a bit more that 3 amps, but all of them dropped in voltage when my pi 3B+ had difficult tasks. After running longer on these standard chargers the Pi would reboot and so the data on the SDcard would corrupt a bit.
This Official Raspberry Pi 3 Power supply has none of the disadvantages.”